English study companion · 2026-08-24
A practical, English-only word list drawn from Atlas of the Moon and The Moon and How to Observe It, with concise definitions and carefully selected sentences from the books.
The baseline comes from the official 2016 College English curriculum vocabulary appendix. Unstarred entries were treated as the CET-4 family baseline; starred entries were treated as CET-6. The source file SHA-256 is 9166d3c03b7bc43abd9d9df91bd2ef8085b4419286f1e5ca100dea68f3cfd1f1.
Words absent from the parsed CET-4 forms were then reviewed with ordinary linguistic judgment. Transparent inflections, obvious derivatives of CET-4 words, personal and lunar-feature names, abbreviations, OCR fragments, and items without a reliable complete source sentence were excluded. Scientific terms were retained when they are genuinely useful for reading the two books.
The official appendix states 5,418 entries, while extraction produced 5,426 logical lines. That eight-line discrepancy is disclosed rather than silently normalized. Every published item received a final word-by-word review.
No entries match this search.
a shortened form of a word or phrase
In this atlas, both on the maps and throughout the text, the abbreviations E (for east) and W (for west) are used instead of the signs + and −.
Atlas of the Moon — PDF p. 11The abbreviations N (for north) and S (for south) are often used instead of the corresponding signs + and −.
Atlas of the Moon — PDF p. 11a defect in an optical system that prevents an exact or undistorted image
Their unsophisticated optical configuration produces false color (chromatic aberration), which becomes obvious when bright objects like the Moon are viewed.
The Moon and How to Observe It — PDF p. 241They suffer greatly from chromatic aberration caused by the splitting of light into its component colors after it is refracted through glass, and spherical aberration caused by light not being brought to a single focus.
The Moon and How to Observe It — PDF p. 246unsuccessful or ending before completion
After several abortive attempts, probes of the second series (Lunas 5–14, 1965–1968) achieved the first soft landing on the Moon (Luna 9, 1966) and established the first artificial lunar satellite (Luna 10, 1966).
Atlas of the Moon — PDF p. 99to exist in large numbers or amounts
Craters up to 50 km in diameter abound.
The Moon and How to Observe It — PDF p. 79an additional component used to improve or extend the function of equipment
An accessory called a teleconverter increases the focal length of a telephoto lens (see Table 2.2).
The Moon and How to Observe It — PDF p. 96Electric focusers enable the focus to be adjusted remotely from the telescope, and they are considered an essential accessory to the lunar imager, not a luxury.
The Moon and How to Observe It — PDF p. 103designed to reduce color fringing caused by different wavelengths focusing separately
Achromatic refractors introduce a degree of false color, not usually a problem when the observer is studying topography alone, but distracting if a TLP search is being attempted.
The Moon and How to Observe It — PDF p. 45Finderscopes have achromatic objective lenses (typically 20–50mm) and have fixed eyepieces that can be adjusted for focus.
The Moon and How to Observe It — PDF p. 246sharpness of vision or perception
Lunar features may be used as a test of visual acuity.
The Moon and How to Observe It — PDF p. 105next to or very near something else
One of the best color contrasts can be seen by viewing the adjacent seas of the reddish Mare Serenitatis and the distinctly blue Mare Tranquillitatis.
The Moon and How to Observe It — PDF p. 45In many instances, features (or groups of features) of interest that lie on, or extend beyond, the edges of the maps may be mentioned, but there is minimal repetition in the descriptions of adjacent areas.
The Moon and How to Observe It — PDF p. 129to be next to and share a boundary with
A highly eroded, irregular crater, de la Rue (136 km), at the far eastern end of the mare, contrasts with the sharp-rimmed craters Strabo (55 km) and Thales (32 km) that adjoin it.
The Moon and How to Observe It — PDF p. 142Further east, the prominent duo of Zagut (84 km) and Rabbi Levi (81 km) adjoin the prominent western wall of a large and otherwise considerably eroded unnamed crater, elongated east–west (105 × 130 km).
The Moon and How to Observe It — PDF p. 218the arrival or introduction of an important new thing
Until the advent of photography in the 19th Century, drawing at the eyepiece was the only means of recording the Moon’s features.
The Moon and How to Observe It — PDF p. 82concerned with beauty or the visual appeal of something
The lunar observer isn’t some kind of weird nocturnal art student – nobody is allocating marks for artistic flair or the aesthetic appeal of an observational drawing.
The Moon and How to Observe It — PDF p. 84While color can enhance the aesthetic quality of an image, it can also be undesirable.
The Moon and How to Observe It — PDF p. 100at or from a great distance
In comparing the Earth with the Moon from afar, it would appear that no two bodies could be so entirely dissimilar in history, composition, form and appearance.
The Moon and How to Observe It — PDF p. 72Nothing of the satellite’s surface can be seen from afar because it is wrapped in a thick, yellow blanket of nitrogen and methane.
The Moon and How to Observe It — PDF p. 78far from the place or area being considered
A small proportion of material found in any spot will come from much further afield, debris thrown out by distant impacts hundreds of kilometers away.
The Moon and How to Observe It — PDF p. 27Further afield, the bright rays commence their long paths in all directions across the Moon’s surface.
The Moon and How to Observe It — PDF p. 189using an optical arrangement in which incoming and outgoing rays are parallel
Afocal Photography Afocal photography – photographing an object through the telescope eyepiece with the camera’s lens also in place – can be performed with both conventional film cameras and digital cameras with fixed lenses.
The Moon and How to Observe It — PDF p. 93Even with such limitations, afocal photography through such a basic camera can produce pleasing results.
The Moon and How to Observe It — PDF p. 93a small tool that sprays paint or ink using compressed air
The airbrush technique of relief representation, which was developed in the early 1960s in the USA for the production of the 1:1,000,000 LAC series of charts, has proved to be the most convenient one.
Atlas of the Moon — PDF p. 11For printing purposes and distinct representation, photographs of selected parts of the lunar surface were either adjusted or completely redrawn using the airbrush technique.
Atlas of the Moon — PDF p. 112similar or closely related
At the other extreme, the path taken by the waning Moon at last quarter in spring is akin to that of the Sun in midwinter—very low in the sky.
Atlas of the Moon — PDF p. 8the fraction of incoming light reflected by a surface
Conversely, some albedo features are quite invisible when near the morning or evening terminator, but stand out boldly under a high Sun.
The Moon and How to Observe It — PDF p. 45Some of the Moon’s brighter albedo features are noticeable even when they are not directly illuminated by the Sun, but instead bathed in the glow of earthshine.
The Moon and How to Observe It — PDF p. 45although
So we now have a credible outline of the Moon's history, albeit with many gaps and unanswered questions awaiting further clarification in the years to come.
Atlas of the Moon — PDF p. 11If, for example, the eastern limb of the Moon is turned toward the Earth, the boundary of the visible part can slide over to the very eastern shores of Mare Marginis and Mare Smythii, and almost the whole areas of these maria will come into view (albeit considerably foreshortened).
Atlas of the Moon — PDF p. 93to bring into a common line, orientation, or precise position
When the Moon is near new or full phase, the Earth, Moon and Sun are aligned – a phenomenon known as syzygy.
The Moon and How to Observe It — PDF p. 54Given that the view through the camera will not be visible during photography, the Moon must be kept precisely aligned through the cross hairs of an accurately aligned viewer.
The Moon and How to Observe It — PDF p. 93an arrangement in a straight line or a precisely adjusted relative position
If the image drifts too much during the clip, the software used to process the video clip may not be able to produce a good alignment.
The Moon and How to Observe It — PDF p. 102The alignment of both the primary mirrors can usually be adjusted by hand, using three wingnuts at the base of the mirror cell, but the secondary will usually require a small screwdriver or allen key.
The Moon and How to Observe It — PDF p. 248to make a problem or harmful effect less severe
Cheap, small telescopes attempt to alleviate the worst effects of aberration by having large stops placed inside the telescope tube, preventing the outer parts of the cone of light from traveling down to the eyepiece.
The Moon and How to Observe It — PDF p. 246to assign or distribute for a particular purpose
The lunar observer isn’t some kind of weird nocturnal art student – nobody is allocating marks for artistic flair or the aesthetic appeal of an observational drawing.
The Moon and How to Observe It — PDF p. 84an annual reference containing calendars and astronomical or other tabulated data
The values of libration in latitude and longitude are available in most astronomical almanacs.
Atlas of the Moon — PDF p. 7The period when an area of interest will be close to the terminator can be determined beforehand by referring to the colongitude tables on page 218 or by consulting an astronomical almanac or a computer program.
Atlas of the Moon — PDF p. 108using movement in altitude and azimuth, or a mount that provides those two motions
Altazimuth Mounts Altazimuth mounts enable the telescope to be moved up and down (in altitude) and from side to side (in azimuth).
The Moon and How to Observe It — PDF p. 254Better altazimuth models are provided with slow-motion knobs that allow the telescope to be moved without having to push its tube around.
The Moon and How to Observe It — PDF p. 254occurring by turns, or to switch repeatedly between two things
Diurnal libration can appear something like the parallax effect produced by an alternate left- and right-eye views of a tennis ball placed 10 m away.
The Moon and How to Observe It — PDF p. 57It is entirely possible to mount these filters side-by-side on a card, and manually alternate them in front of an eyepiece that has a good level of eye relief.
The Moon and How to Observe It — PDF p. 234an instrument that measures height or altitude
The laser altimeter of Apollo 15 discovered some exceptionally flat places in Oceanus Procellarum with height differences of ±80 m over a distance of 200 km.
Atlas of the Moon — PDF p. 45open to more than one interpretation or not clearly defined
The maps correspond with those published in the Hatfield Photographic Lunar Atlas published by Springer-V erlag (see the resources section of this book), one of the least ambiguous maps in print, drawn with clear lines and easy to use in the field at the eyepiece.
The Moon and How to Observe It — PDF p. 129a change or addition made to improve or correct something
Lunar nomenclature has had a long and intricate history—full of mistakes, confusion and amendments, and with many modifications—and finally, a unique selection of names has been created.
Atlas of the Moon — PDF p. 12to increase the strength or magnitude of something
Most of the time atmospheric turbulence, amplified by magnification, forces the observer to use magnifications that are less than what the instrument is capable of.
Atlas of the Moon — PDF p. 107similar in a way that permits a useful comparison
These systems are analogous to the well-known terrestrial coordinates of latitude and longitude, but despite these similarities, there are many differences between the definitions of fundamental planes of reference and orientations, not forgetting the nomenclature.
Atlas of the Moon — PDF p. 111a comparison based on a meaningful similarity between different things
Many of Ariel’s features, like crustal melts and glacial flows, have no analogy with anything seen on the lunar surface.
The Moon and How to Observe It — PDF p. 79measured by or relating to an angle
The Earth–Moon system has the largest amount of angular momentum (a product of the objects’ masses and velocities) in the Solar System; what mechanisms could possibly account for this?
The Moon and How to Observe It — PDF p. 12The average angular diameter of the Moon as seen from the Earth’s surface is 31′05′′.
The Moon and How to Observe It — PDF p. 53relating to the interval between successive passages through perigee
Twice every anomalistic month (the lunar month from perigee to perigee), libration in longitude creates a maximum east–west displacement on opposite sides of the Moon’s edge.
The Moon and How to Observe It — PDF p. 57If the Moon’s diameter is measured in this manner over a period of a year, then it becomes clear that the period from one perigee to the next; called the “anomalistic month, ” is shorter than the synodic month (new Moon to new Moon) by a couple of days.
The Moon and How to Observe It — PDF p. 108different from what is normal or expected
Such bouts of anomalous short-lived activity seem to occur sporadically in a number of specific small areas of the lunar surface.
The Moon and How to Observe It — PDF p. 44Colored filters can enhance the visibility of anomalous colored areas on the lunar surface.
The Moon and How to Observe It — PDF p. 232something that differs unexpectedly from the normal pattern
Using the device, it is possible to determine whether a feature is exhibiting a genuine brightness anomaly by comparing it with the brightness of other features in the immediate area.
The Moon and How to Observe It — PDF p. 234a light-colored igneous rock composed mainly of plagioclase feldspar
Minerals like anorthosite would have been less dense than the magma melt, and they floated to the surface, aided by upwelling magmatic convection currents, to accumulate in gigantic “rockbergs” at the Moon’s surface.
The Moon and How to Observe It — PDF p. 18Lighter, less dense minerals like anorthosite would have floated to the surface of the magma melt, aided by upwelling convection currents, accumulating in gigantic “rockbergs,” which became the first substantial crust of the Moon.
The Moon and How to Observe It — PDF p. 19a structure used to transmit or receive radio waves
But in August 1991 a team of astronomers at the California Institute of Technology made an excellent series of radar images of Mercury’s surface, using a high-power beam sent by the Jet Propulsion Laboratory’s Goldstone antenna in California.
The Moon and How to Observe It — PDF p. 71the opening through which light enters an optical instrument
At first glance, they resemble regular binoculars of the same aperture but weigh slightly more, and they can be used like normal binoculars.
The Moon and How to Observe It — PDF p. 242Regardless of a telescope’s aperture or physical size, the most important thing to be aware of when purchasing any telescope is its optical quality.
The Moon and How to Observe It — PDF p. 245a lens or telescope corrected to bring several colors into nearly the same focus
Views of the Moon through an apochromat are almost completely free of distortion and are of high contrast, rivaling the kind of view to be had through a good-quality long-focal-length Newtonian reflector (see below).
The Moon and How to Observe It — PDF p. 247Another, more expensive way to minimize chromatic distortion is to use a specially designed lens (such as a “Chromacorr”) that attaches to the eyepiece, transforming a budget achromatic refractor into a telescope that approaches the performance of a high-end apochromat.
The Moon and How to Observe It — PDF p. 247the point in an Earth-orbiting body's path that is farthest from Earth
The difference in apparent size of the Moon near perigee and apogee.
The Moon and How to Observe It — PDF p. 52Having an apparent diameter about 12% larger at perigee, the apparent area of the perigee Moon is a huge 29% larger than at apogee.
The Moon and How to Observe It — PDF p. 53large or clear enough to be noticed or measured
Types of Lunar Rock The Moon has never possessed an appreciable atmosphere, and its surface has been subjected to none of the processes of erosion found on the Earth.
The Moon and How to Observe It — PDF p. 24The lunar crust has never been subjected to any appreciable tectonic activity, and large-impact features many billions of years old can be clearly traced; some of them were actually formed before life on Earth appeared.
The Moon and How to Observe It — PDF p. 28a broad area or deposit spreading outward from a central feature
A curious bright apron extending 20 km is formed by the rays immediately north of the crater.
The Moon and How to Observe It — PDF p. 147the two extreme orbital points, such as apogee and perigee
The imaginary line that joins the points of apogee and perigee – effectively the major axis of the Moon’s elliptical orbit – is called the “line of apsides”.
The Moon and How to Observe It — PDF p. 53The line of apsides rotates (with respect to the stars) in a prograde fashion every 8.85 years.
The Moon and How to Observe It — PDF p. 53a curved segment or an angular measure on a circle
Atmospheric Phenomena Lunar rainbows are created under the same circumstances as rainbows produced by the Sun: a colored arc of 42° radius situated directly opposite the light source.
The Moon and How to Observe It — PDF p. 63Occultation studies that accurately measure the drop in light at occultation have revealed Aldebaran to have a diameter of 20 milliseconds of arc – the apparent diameter of a star 50 km away.
The Moon and How to Observe It — PDF p. 66to curve upward, or a curved structure
It is possible, though, that some domes are uplift features like the Adirondack Mountains in New Y ork State, where deep intrusions of magma have forced the overlying layers of rock to arch upwards.
The Moon and How to Observe It — PDF p. 118a collection of historical records, images, or data
Artist and photographer Michael Light drew on NASA ’s original photographic archives to assemble an archetypal lunar journey in images, from take-off to landing.
The Moon and How to Observe It — PDF p. 270curved like a bow or arc
Many prominent graben cut across lunar maria, parallel to mare borders; these are known as arcuate rilles because of their curving paths.
The Moon and How to Observe It — PDF p. 41Prominent arcuate rilles lie near the southwestern border of Mare Tranquillitatis and the western and southeastern border of Mare Humorum.
The Moon and How to Observe It — PDF p. 41an ordered arrangement or a large and varied group of things
CCDs in low-end digicams may have an array of 640 × 480 pixels, while a more expensive digicam CCD may boast 2240 × 1680 pixels (around 4 megapixels).
The Moon and How to Observe It — PDF p. 99Digital Imaging A CCD is a small flat chip, about the diameter of a matchhead in most commercial digicams, made up of an array of tiny light-sensitive elements called pixels.
The Moon and How to Observe It — PDF p. 99an artificial feature or error introduced by a method, instrument, or processing step
Stippling in too regimented a fashion – along straight lines, for example – may give rise to unwelcome artifacts.
The Moon and How to Observe It — PDF p. 88The airy pattern, an artifact introduced by optics, will distort according to the degree of atmospheric turbulence along its light path.
The Moon and How to Observe It — PDF p. 89to move upward or climb
Through a telescope the scarp may appear as a steep slope, but it is not as precipitous as appearances might suggest: it has a gradient of about 7°, so gentle that it could be ascended without much difficulty.
The Moon and How to Observe It — PDF p. 185to discover or determine something with certainty
With practice, a feature’s apparent brightness during the lunar day can be ascertained, along with features in the target’s immediate vicinity.
The Moon and How to Observe It — PDF p. 234to attribute something to a particular cause or source
These brightenings have been ascribed to the lunar rocks fluorescing as the solar particles impacted on them.
The Moon and How to Observe It — PDF p. 45Even using a good telescope under ideal conditions, the inexperienced lunar observer may not expect to see obvious hues of purple, brown, red, green and blue on the Moon, and their presence may wrongly be ascribed to some kind of anomalous event.
The Moon and How to Observe It — PDF p. 45not straight, level, or correctly aligned
Planets far bigger than the Earth have been knocked askew by cosmic collision.
The Moon and How to Observe It — PDF p. 18Active geysers shoot material up to 20 km above Triton’s surface and are blown askew by high-altitude winds.
The Moon and How to Observe It — PDF p. 79a violent attack or damaging impact
Global maps would be dramatically different had the Earth escaped repeated major cosmic assaults.
The Moon and How to Observe It — PDF p. 72a confident statement or claim
Current geophysical theories do not support this assertion – the Atlantic basin itself is a very young feature, just 130 million years old.
The Moon and How to Observe It — PDF p. 14These assertions were sensationalist and based on poor science.
The Moon and How to Observe It — PDF p. 48the process by which one material is incorporated into another
The Mg-suite rocks date from around 4.5 to 4.2 billion years, and were formed by a process of assimilation in numerous magmatic intrusions into the anorthositic crust.
The Moon and How to Observe It — PDF p. 26of various different kinds grouped together
According to the theory of co-accretion, around 4.6 billion years ago, the Moon condensed from a primordial cloud of gas, dust and assorted debris in orbit around the Earth.
The Moon and How to Observe It — PDF p. 14Crossstaffs and assorted naked eye devices were used extensively in the pretelescopic era, and they are easy to construct.
The Moon and How to Observe It — PDF p. 108a small rocky or metallic body orbiting the Sun
Breccia is a composite rock made up of fragments created through the processes of impact shattering, mixing, melting and recrystallization of rock during the high energies released during meteoroid and asteroid impacts.
The Moon and How to Observe It — PDF p. 26Jupiter’s Lagrangian points, for example, are occupied by the Trojan asteroid groups that orbit the Sun at the same distance and in the same plane as Jupiter, but 60° preceding and following the giant planet.
The Moon and How to Observe It — PDF p. 67relating to or resembling asteroids
The theory may explain the similar crater-sculpted faces of the Moon and Mercury, caused when both objects encountered asteroidal debris in the inner Solar System.
The Moon and How to Observe It — PDF p. 16The unique chemical makeup of KREEP enables it to be used as a chemical tracer to chart the convoluted history of lunar volcanism and asteroidal bombardment.
The Moon and How to Observe It — PDF p. 19photography of celestial objects and astronomical phenomena
When beginning in astrophotography, it is also essential to make a written record of the precise exposures, film type and lunar phase so that you can identify an optimum combination that can be repeated in the future.
The Moon and How to Observe It — PDF p. 98not symmetrical or not identical on opposite sides
Experiments have shown that such asymmetric rays are produced by high-velocity impactors that approach the Moon’s surface at angles shallower than 7°.
The Moon and How to Observe It — PDF p. 36Brilliant crater in Oceanus Procellarum, the center of an asymmetric ray system traceable for 300 km to its east.
The Moon and How to Observe It — PDF p. 122a systematically arranged collection of maps, charts, or plates
Many older atlases may contain errors of nomenclature or outmoded and unofficial designations for features. “Pickering, ” for example, was a name once unofficially given to Messier A in Mare Fecunditatis.
The Moon and How to Observe It — PDF p. 88to be available or useful for a purpose
Eyepiece-projection adapters are widely available.
Atlas of the Moon — PDF p. 108to turn away, especially the eyes or attention
For example, a small crater lying some distance from a feature under scrutiny can appear to completely vanish from sight, while features in the terrain surrounding the crater remain visible; of course, this effect is noticeable only through averted vision, and is cancelled out immediately when the eye flicks onto the affected area.
The Moon and How to Observe It — PDF p. 240relating to or situated around an axis
A collision between the embryonic Mercury and Venus may account for their unusual properties – Mercury’s huge iron core and Venus’s slow, retrograde axial rotation.
The Moon and How to Observe It — PDF p. 18But the lunar poles are actually tilted 6.4° to its orbital plane, and the axial tilt remains fixed in one direction in space.
The Moon and How to Observe It — PDF p. 57horizontal angular direction measured around the horizon
Altazimuth Mounts Altazimuth mounts enable the telescope to be moved up and down (in altitude) and from side to side (in azimuth).
The Moon and How to Observe It — PDF p. 254Dobsonians consist of a ground box with an azimuth bearing and another box that holds the telescope tube.
The Moon and How to Observe It — PDF p. 254a barrier inside an optical instrument that blocks stray light
The optical surfaces are usually multicoated to minimize reflections, and internal baffles block stray light and internal reflections, providing better contrast.
The Moon and How to Observe It — PDF p. 243empty, lifeless, or unable to support growth
Although the Moon appears to be a barren and entirely dead world, there have been occasional reports – mainly from amateur lunar observers – of small-scale transient changes on the Moon’s surface called TLP (transient lunar phenomena).
The Moon and How to Observe It — PDF p. 44the common center of mass around which two or more bodies orbit
If the Earth and Moon were equal in all respects, then the barycenter would be positioned in space exactly between the Earth and Moon.
The Moon and How to Observe It — PDF p. 52In fact, both the Earth and Moon revolve about their common center of gravity, a point called the barycenter.
The Moon and How to Observe It — PDF p. 52a dark, fine-grained volcanic rock formed from cooled lava
Basalt is a dark-colored volcanic rock that once flowed as lava and filled all the marial basins of the near side and some areas on the far side.
The Moon and How to Observe It — PDF p. 25Basalt, anorthosite and breccia make up the three main types of lunar rock.
The Moon and How to Observe It — PDF p. 25composed of, containing, or resembling basalt
Basaltic in composition, the marial lava flows had the viscosity of motor oil and were ductile and fast-moving.
The Moon and How to Observe It — PDF p. 20The youngest lunar rocks – the basaltic lava that filled the near-side impact basins – date from around 3 billion years, which makes them about as old as the oldest rocks found on the Earth.
The Moon and How to Observe It — PDF p. 24to strike repeatedly and damage or erode
One of the Moon’s most eroded named craters, the extremely battered Louville (36 km) can be just made out on the shore of a small bay in Sinus Roris.
The Moon and How to Observe It — PDF p. 168Scheiner, to its immediate northwest, is a considerably more ancient feature, its wall and floor having been battered and eroded by multiple impacts.
The Moon and How to Observe It — PDF p. 192a small rounded drop, particle, or object
A micrometeorite impact pit in a tiny glassy bead sampled from the lunar soil.
The Moon and How to Observe It — PDF p. 33Some larger fragments may be hastily welded together in breccias, while smaller droplets of material may cool and solidify in flight, forming tiny glassy beads or larger “bombs.” The ejecta itself is deposited in an ordered manner.
The Moon and How to Observe It — PDF p. 30solid rock underlying loose surface material
The material originally nearer the surface is ejected furthest, while deeper bedrock is lobbed shorter distances from the rim.
The Moon and How to Observe It — PDF p. 31Beyond the rim there is a considerable amount of physical structure, including prominent radial ridges and grooves, in addition to secondary cratering caused by the impact of substantial chunks of excavated bedrock.
The Moon and How to Observe It — PDF p. 32convex on both surfaces
In their most basic form, they consist of small biconvex objective lenses and biconcave eye lenses, and these form an upright image.
The Moon and How to Observe It — PDF p. 241A monocentric eyepiece consists of a meniscus lens cemented to either side of a biconvex lens.
The Moon and How to Observe It — PDF p. 252designed for viewing with both eyes, or a two-eyed optical instrument
A binocular view of the crescent Moon, its dark side adorned with blue earthshine, is utterly beautiful.
The Moon and How to Observe It — PDF p. 111For binocular studies of the Moon, the higher the magnification, the better; with the exception of zoom binoculars and specialist giant binoculars, most binoculars give magnifications of between 7 and 15×.
The Moon and How to Observe It — PDF p. 111a two-eyed optical instrument for viewing distant objects
The ashen glow of this twice-reflected light is called “earthshine,” a faint glow on the unilluminated portion of the Moon, often visible with the unaided eye and striking through binoculars.
The Moon and How to Observe It — PDF p. 60A pair of good-quality binoculars reveal a considerable amount of lunar detail.
The Moon and How to Observe It — PDF p. 111the regions of a world where life exists, considered as a system
Only one world we know of – our own Earth – has a dynamic biosphere.
The Moon and How to Observe It — PDF p. 69The topographic evidence for ancient bombardment has largely been obliterated by the powerful forces of plate tectonics and vulcanism, in conjunction with the dynamic atmosphere, hydrosphere and biosphere.
The Moon and How to Observe It — PDF p. 72lacking strong or distinctive features
Europa is the smoothest, most topographically bland satellite in the Solar System: its features are comparable in magnitude to pencil markings on a pool ball.
The Moon and How to Observe It — PDF p. 77Around Mons Rümker, the marial plains are crossed by one or two very inconspicuous wrinkle ridges and are dusted with a few rays, and it is one of the most topographically bland areas on the entire Moon.
The Moon and How to Observe It — PDF p. 178to appear and disappear rapidly or intermittently
The edge of the Moon is quite irregular, and grazing stars can appear to blink on and off several times as they disappear behind hills and mountains and reappear in lunar valleys.
The Moon and How to Observe It — PDF p. 67There are a number of features on the Moon that will appear to blink naturally, among them being the southwestern part of the crater Fracastorius and a section of the western wall of Plato.
The Moon and How to Observe It — PDF p. 234sustained or repeated impacts by projectiles or space debris
The unique chemical makeup of KREEP enables it to be used as a chemical tracer to chart the convoluted history of lunar volcanism and asteroidal bombardment.
The Moon and How to Observe It — PDF p. 19All of the terrestrial planets – Mercury, Venus, Mars and the Earth – are thought to have been subjected to similar levels of bombardment, but only Mercury’s surface resembles that of the Moon.
The Moon and How to Observe It — PDF p. 27a short period or episode of an activity or condition
Such bouts of anomalous short-lived activity seem to occur sporadically in a number of specific small areas of the lunar surface.
The Moon and How to Observe It — PDF p. 44In addition to elusive bouts of short-lived TLP activity, lunar changes of a permanent nature have also been suggested; there are a number of alleged cases.
The Moon and How to Observe It — PDF p. 47interwoven or arranged like strands in a braid
A braided wrinkle ridge runs southwest of Lansberg past the flooded crater Lansberg C (17 km) and the small, bright-ray crater Lansberg D (9.5 km) to converge with several more complex wrinkle ridges in Oceanus Procellarum.
The Moon and How to Observe It — PDF p. 180an opening made by breaking through a wall or boundary, or to make such an opening
The crater’s northern wall is breached by a broad, roughly hewn valley some 18 km long, at the northern end of which sits a prominent 7 km bowl-shaped crater.
The Moon and How to Observe It — PDF p. 171Eddington shares its low western wall with the broad low-walled plain of Struve, which is linked with Russell to the north by a broad breach in its northern wall.
The Moon and How to Observe It — PDF p. 173rock composed of angular fragments cemented together
Breccia is a composite rock made up of fragments created through the processes of impact shattering, mixing, melting and recrystallization of rock during the high energies released during meteoroid and asteroid impacts.
The Moon and How to Observe It — PDF p. 26Breccias are described as monomict if they contain fragments of only one rock type; most breccias are polymict and are composed of more than one type of rock.
The Moon and How to Observe It — PDF p. 26quick, energetic, or moderately fast
It follows that at the equator the speed of the Moon’s terminator is, on average, about 15 km per hour (a brisk jogging speed) taking 29.5 days to make a complete circuit about the Moon, with its circumference of 10,920 km, from one sunrise/set to the next.
The Moon and How to Observe It — PDF p. 62to loom or remain in a dark, heavy, or threatening manner
North of these brooding sentinels, cratered, hilly terrain rises from the flat expanses of Oceanus Procellarum (Ocean of Storms) to the west and blends into Montes Jura, a magnificent arc of peaks.
The Moon and How to Observe It — PDF p. 115Pitatus broods over Mare Nubium’s southern shoreline.
The Moon and How to Observe It — PDF p. 180something that absorbs or reduces the effect of an impact
Through the eons, the substantial atmospheres of Venus, the Earth and Mars have served as an effective impact buffer, allowing only a few of the biggest incoming objects to wreak large-scale damage.
The Moon and How to Observe It — PDF p. 27a rounded swelling that projects beyond a surrounding surface
As the Moon raises tidal bulges in the Earth’s oceans, friction between the ocean masses and the Earth’s crust acts like a brake, gradually decelerating the Earth’s rate of spin.
The Moon and How to Observe It — PDF p. 13Because the inner regions of the protoplanet became more massive, there was a gradual acceleration in its axial rotation, and centrifugal forces gave rise a pronounced equatorial bulge.
The Moon and How to Observe It — PDF p. 13the chemical element with atomic number 20
Typically around 50% of lunar basalt comprises the mineral pyroxene, a calcium–magnesium–iron silicate.
The Moon and How to Observe It — PDF p. 25a deep valley with steep sides
Vallis Marineris, to the southeast of Tharsis, is a vast canyon produced by crustal rifting.
The Moon and How to Observe It — PDF p. 74For example, the base of Hadley Rill, a large lunar canyon on the eastern border of Mare Imbrium, is covered with a thick blanket of soil embedded with sizable boulders that have fallen from the higher slopes.
The Moon and How to Observe It — PDF p. 49a headland that projects into a sea or other broad expanse
Luna 17, which landed to the south of Cape Heraclides, transported an automatic mobile laboratory, Lunokhod 1, to the Moon.
Atlas of the Moon — PDF p. 26a person who creates or studies maps
The Consolidated Lunar Atlas (ref. 11), published in 1967, is still the best and most detailed Earth-based photographic atlas of the Moon; it shows the individual surface areas under different solar-illumination angles, which is essential for the work of the cartographer.
Atlas of the Moon — PDF p. 112relating to the creation or design of maps
A cartographic representation of the lunar surface can be schematic, generalized, or realistically detailed.
Atlas of the Moon — PDF p. 11The mapping starts with the selection of a suitable cartographic projection, which in turn involves consideration of the scale of the map and the number of sections into which it is to be divided.
Atlas of the Moon — PDF p. 11the science and practice of making maps
Old general maps, full of other glaring errors in cartography, can hardly be used as evidence, and many historical observations of Linné are contradictory.
The Moon and How to Observe It — PDF p. 48a standard type of thick, smooth drawing paper
To make regular pencil sketches, a good range of soft-leaded pencils and a small pad of smooth cartridge paper are recommended.
The Moon and How to Observe It — PDF p. 84My own preference – soft pencil on smooth cartridge paper – is by far the quickest and least fussy medium.
The Moon and How to Observe It — PDF p. 87to cut, wear, or excavate a shape or feature into a surface
This debris may have carved out some of the large lunar-impact scars – certainly, some of the ancient impact basins correspond in age with the proposed era of capture.
The Moon and How to Observe It — PDF p. 17The origin of the scarp is linked to the stresses set up in the lunar crust by the asteroidal impact that carved the Nectaris impact basin.
The Moon and How to Observe It — PDF p. 125using both lenses and mirrors, or an optical instrument of this type
Catadioptrics Catadioptric telescopes use a combination of mirrors and lenses to collect and focus light.
The Moon and How to Observe It — PDF p. 249There are two popular forms of catadioptric – the Schmidt-Cassegrain telescope (SCT) and the Maksutov-Cassegrain telescope (MCT).
The Moon and How to Observe It — PDF p. 249a sudden event causing great damage or destruction
Current theories about the extinction of many dinosaur species credit this crater with having just the right age, size and location to have been responsible for this catastrophe.
The Moon and How to Observe It — PDF p. 73It is estimated that during the past 600 million years, some 2,000 major impact events have occurred on the Earth. Yet even this phase must be regarded as quiescent compared with the cosmic catastrophes of several thousands of millions of years ago.
The Moon and How to Observe It — PDF p. 72causing or involving sudden and extensive destruction
Life has had an immense effect upon our planet’s external appearance, and human activity now has the potential to trigger a more vigorous, and potentially catastrophic, pace of change.
The Moon and How to Observe It — PDF p. 69Like Gaspra, Ida displays grooves indicating that it was once part of a larger body that experienced a catastrophic fragmentation.
The Moon and How to Observe It — PDF p. 75a chain of craters in planetary nomenclature
Across the mare due south of Eddington, Krafft (51 km) is joined with Cardanus (50 km) by Catena Krafft (60 km long), a small continuous crater chain that can be discerned through a 100 mm telescope.
The Moon and How to Observe It — PDF p. 173Running across the eastern part of its floor is Catena Davy, a crater chain that can be traced 50 km to the bright impact crater of its origin, Davy G (12 km).
The Moon and How to Observe It — PDF p. 181a hollow space or depression within a solid body
A plume of ejecta is thrown up from the Moon’s surface as the edge of the explosion cavity is deformed and uplifted.
The Moon and How to Observe It — PDF p. 31relating to the sky or objects in space
If the Moon’s orbit were circular and the plane happened to coincide with the celestial equator, all retardations would be around the same length.
The Moon and How to Observe It — PDF p. 62Lunar Occultations When a distant celestial object, be it a star, planet or deep sky object, is temporarily hidden from view by the Moon, a lunar occultation takes place.
The Moon and How to Observe It — PDF p. 66directed or appearing to act outward from a center of rotation
It saw the Earth and Moon as having once been joined in a hot rotating body whose rapid spin created centrifugal forces powerful enough to fling off the material of the Moon.
The Moon and How to Observe It — PDF p. 13One theory suggests that the Moon was a mere by-product of an Earth–Mars centrifugal separation – a smaller “droplet” of material that appeared between the two main planets.
The Moon and How to Observe It — PDF p. 14an enclosed cavity or compartment
This lens focuses light across a chamber filled with vitreous humor, a clear jelly that gives the eyeball its rigidity, and an upside-down image is projected onto the retina inside the back part of the eyeball.
The Moon and How to Observe It — PDF p. 239relating to color, especially color effects in an optical system
Their unsophisticated optical configuration produces false color (chromatic aberration), which becomes obvious when bright objects like the Moon are viewed.
The Moon and How to Observe It — PDF p. 241Apochromatic refractors use special glass in their 2- or 3-element objective lenses to bring the light to a tack-sharp focus, delivering images that are virtually free from the effects of chromatic distortion.
The Moon and How to Observe It — PDF p. 247a thick or substantial piece of material
The Moon is a chunk of material spun off from a rapidly revolving Earth.
The Moon and How to Observe It — PDF p. 12Beyond the rim there is a considerable amount of physical structure, including prominent radial ridges and grooves, in addition to secondary cratering caused by the impact of substantial chunks of excavated bedrock.
The Moon and How to Observe It — PDF p. 32the distance around a circle or rounded body
Mare Imbrium is surrounded for 300° of its circumference by the most spectacular series of mountain ranges on the Moon’s near side.
The Moon and How to Observe It — PDF p. 115It follows that at the equator the speed of the Moon’s terminator is, on average, about 15 km per hour (a brisk jogging speed) taking 29.5 days to make a complete circuit about the Moon, with its circumference of 10,920 km, from one sunrise/set to the next.
The Moon and How to Observe It — PDF p. 62the removal or sale of remaining stock
Unfortunately, newspaper advertisements announcing massive stock clearances of telescopes and binoculars are often full of outrageous hyperbole, with claims of extravagant magnifications and the ability of the instrument to show all the wonders of the Universe.
The Moon and How to Observe It — PDF p. 245a close group of similar objects
The Moon’s near side has 18 named mountain ranges and 30 individually named mountains, but there are many more small, unnamed mountain peaks and peak clusters within the maria.
The Moon and How to Observe It — PDF p. 43The famous Henbury crater cluster, just south of Alice Springs, encompasses an oval area of some 1.25 sq km.
The Moon and How to Observe It — PDF p. 73a tight grasp or controlling hold
It is the only planetary satellite currently in the clutches of active vulcanism, and its surface features are the newest in the entire Solar System.
The Moon and How to Observe It — PDF p. 77to occur at the same position, time, or condition
If the Moon’s orbit were circular and the plane happened to coincide with the celestial equator, all retardations would be around the same length.
The Moon and How to Observe It — PDF p. 62Over 2 years later, the ellipse’s major axis has rotated so that it is perpendicular to the Sun’s direction; apogee or perigee then coincides with either the first or last quarter, and by this time the orbital ellipse will have been gradually pulled back into a less eccentric shape.
The Moon and How to Observe It — PDF p. 55an occurrence in which events or properties agree unexpectedly
One of the Solar System’s greatest coincidences is the fact that both the Sun and Moon have an apparent angular diameter of around half a degree as viewed from the Earth’s surface.
The Moon and How to Observe It — PDF p. 64It is probably no coincidence that most TLP activity takes place in areas that have succumbed to substantial crustal stress and display extensive, deep-seated faulting – around mare borders and on the fractured floors of some craters.
The Moon and How to Observe It — PDF p. 47to strike another moving or stationary body
New crustal material is supplied by the mantle as active volcanic ridges push oceanic plates apart, causing them to collide with continental crust at its margins.
The Moon and How to Observe It — PDF p. 42Over the eons, innumerable meteoroids, asteroids and cometary nuclei have collided with the Moon.
The Moon and How to Observe It — PDF p. 69the precise alignment of optical components along a common axis
German-style Porro prism binoculars feature objective housings that screw into the main body containing the prisms; their modular nature makes them more susceptible to going out of collimation after knocks.
The Moon and How to Observe It — PDF p. 243Collimation can be time-consuming and a little tricky for novices, but new telescopes should be provided with adequate instructions, and there are many internet resources that explain the process in detail.
The Moon and How to Observe It — PDF p. 248an event in which moving bodies strike one another
The Moon was formed from material thrown out from the Earth after a planetary collision.
The Moon and How to Observe It — PDF p. 13So, the idea that a much smaller planetary collision brought about the Moon’s birth has now gained great respectability among planetary scientists.
The Moon and How to Observe It — PDF p. 18the selenographic longitude of the morning terminator measured westward from the lunar prime meridian
At new Moon, the Sun’s selenographic colongitude equals 270°, at first quarter 90°, full Moon 180° and last quarter 180°.
The Moon and How to Observe It — PDF p. 91In order to calculate precisely where the morning or evening terminator of the Moon lies, a figure called the Sun’s selenographic colongitude is used (see Table 4.1).
The Moon and How to Observe It — PDF p. 91the color or pattern of colors visible in something
Some areas of the Moon do possess delicate, but noticeable, coloration, and the observed intensity of these colors varies with their illumination.
The Moon and How to Observe It — PDF p. 45It may be an area where volcanic gases have vented, causing a change in the coloration of the surface materials.
The Moon and How to Observe It — PDF p. 176an icy small body that may form a coma and tail when near the Sun
Atmosphereless Mercury and the Moon have been fully exposed to the harsh vacuum of space and subjected to bombardment by interplanetary dust, meteoroids, asteroids and comets, in addition to x-rays, gamma rays and cosmic rays.
The Moon and How to Observe It — PDF p. 27The supply of these objects is constantly being replenished as the Moon’s gravity sweeps up material, much of it micrometeoroidal debris left in the wake of comets.
The Moon and How to Observe It — PDF p. 68relating to or originating from a comet
Gone are the days when our own little corner of the Universe was viewed as a place of eternal tranquility, save for the occasional cometary visitor.
The Moon and How to Observe It — PDF p. 18Over the eons, innumerable meteoroids, asteroids and cometary nuclei have collided with the Moon.
The Moon and How to Observe It — PDF p. 69to collect information and arrange it into a single work or dataset
Having received the radar reflections at New Mexico’s Very Large Array radio telescope, the data was compiled into a map.
The Moon and How to Observe It — PDF p. 71to add to or combine with something to produce a complete effect
At syzygy, the Sun’s gravitational attraction complements that of the Moon, producing the most pronounced tidal bulges.
The Moon and How to Observe It — PDF p. 54combining in a way that completes or improves each part
Both programs were complementary to each other and produced a rich harvest of new data about the Moon.
Atlas of the Moon — PDF p. 99made from several distinct parts or materials
Breccia is a composite rock made up of fragments created through the processes of impact shattering, mixing, melting and recrystallization of rock during the high energies released during meteoroid and asteroid impacts.
The Moon and How to Observe It — PDF p. 26to press into a smaller volume or denser state
The crust beneath the impactor is compressed and the surrounding material is pushed downwards and outwards.
The Moon and How to Observe It — PDF p. 30Immediately following the impact, the compressed crust rebounds, forming a central elevation.
The Moon and How to Observe It — PDF p. 31the action or state of being pressed into a smaller volume
Although some upland areas may be true volcanoes, none of the Moon’s mountains have been caused by tectonic-driven crustal compression.
The Moon and How to Observe It — PDF p. 42Most of the dorsa are compression features, formed when the mare lavas subsided, reducing the marial surface area and crumpling mare material in a gradual manner.
The Moon and How to Observe It — PDF p. 118curved inward like the inside of a bowl
Plotted to scale and viewed from above, the path of the Moon around the Earth is always concave to the Sun.
The Moon and How to Observe It — PDF p. 52The most popular reflecting telescope design, the Newtonian, uses a concave primary mirror held in a cell at the bottom of the tube and a smaller flat secondary mirror mounted on a “spider” near the top of the tube, which reflects light sideways through the tube into the eyepiece.
The Moon and How to Observe It — PDF p. 248sharing the same center
Many of the bigger, generally unflooded far-side impact basins display central massifs and a system of concentric mountain rings.
The Moon and How to Observe It — PDF p. 43a solid or surface tapering from a circular base to a point
The umbra is the darkest part of the shadow and is a cone of deep shadow formed by the external common tangents of the Sun and the object.
The Moon and How to Observe It — PDF p. 63An umbral shadow cone over 1.3-million-km long is cast by the Earth.
The Moon and How to Observe It — PDF p. 64the arrangement of the parts of a system or object
Their unsophisticated optical configuration produces false color (chromatic aberration), which becomes obvious when bright objects like the Moon are viewed.
The Moon and How to Observe It — PDF p. 241Numerous optical configurations are used in binoculars, and this is obvious when one looks at the wide variety of different shapes and sizes available.
The Moon and How to Observe It — PDF p. 243joined together or sharing a boundary
One interesting crater thought to have been formed secondary to the Copernicus impact is the keyhole-shaped conjoined craters Fauth (12km) and Fauth A (9.6km), a short distance south of Copernicus, visible through binoculars.
The Moon and How to Observe It — PDF p. 121Conjoined craters Plana (44 km) and Mason (37 km) are depressed into the disintegrated terrain on the southern border of Lacus Mortis.
The Moon and How to Observe It — PDF p. 144following one after another without interruption
In spring, the ecliptic is at a steep angle to the eastern horizon, meaning that around the time of full Moon, its period of retardation is greatest, and consecutive evening rising times are most widely separated.
The Moon and How to Observe It — PDF p. 63In spring the ecliptic is at a steep angle to the eastern horizon, which means that, around the time of full Moon, its consecutive evening rising times are widely separated; sometimes by as much as an hour and a half.
The Moon and How to Observe It — PDF p. 109the preservation of a physical quantity in a closed system
The law of conservation of angular momentum states that in a system like that of the Earth and Moon, the total momentum remains constant.
The Moon and How to Observe It — PDF p. 54easy to notice or clearly visible
A conspicuous absence of large marial plains is the most significant difference between Mercury and the Moon.
The Moon and How to Observe It — PDF p. 70Just west of Maskelyne A lies the tiny crater Censorinus (3.8 km), conspicuous because of its brilliant (25-km-diameter) collar of ejecta.
The Moon and How to Observe It — PDF p. 223a recognized pattern or region of stars in the sky
The inclination of the Moon’s orbit to the ecliptic, combined with the recession of the line of nodes, means that every 18.61 years the Moon attains its most southerly declination below the ecliptic, in the constellation of Sagittarius.
The Moon and How to Observe It — PDF p. 53a component part of a whole
Beneath this layer, some constituents of the core, at a temperature of 1,000°C, are likely to exist in a molten state.
The Moon and How to Observe It — PDF p. 21Mg-suite rocks probably make up a major constituent of the Moon’s lower crust, as they are found in abundance in the ejecta from the major impact basins – impacts large enough to have excavated material from deep within the crust.
The Moon and How to Observe It — PDF p. 26a limitation or condition that restricts possibilities
There are a number of constraints facing current theories of the Moon’s origin.
The Moon and How to Observe It — PDF p. 12to think about or consider carefully
The science and technology of the second half of the 20th century have brought the Moon so close to us that we now regard it much the same way that 15th-century navigators contemplated the exploration of distant continents.
Atlas of the Moon — PDF p. 6to bring about or arrange, often awkwardly or deliberately
The division between each area described does not follow the exact lines of a grid, as this would contrive to split up the descriptions of some features and associated groups of features between areas.
The Moon and How to Observe It — PDF p. 129heat transfer by the movement of a fluid or slowly flowing material
Minerals like anorthosite would have been less dense than the magma melt, and they floated to the surface, aided by upwelling magmatic convection currents, to accumulate in gigantic “rockbergs” at the Moon’s surface.
The Moon and How to Observe It — PDF p. 18Lighter, less dense minerals like anorthosite would have floated to the surface of the magma melt, aided by upwelling convection currents, accumulating in gigantic “rockbergs,” which became the first substantial crust of the Moon.
The Moon and How to Observe It — PDF p. 19to move toward and meet at a common point
Basin formation imparted tremendously powerful seismic waves into the lunar crust, which traveled around the Moon to converge on the other side, immediately opposite the impact site.
The Moon and How to Observe It — PDF p. 37A network of wrinkle ridges 300 km from north to south converges on Lamont, a unique and fascinating feature in southwestern Mare Tranquillitatis.
The Moon and How to Observe It — PDF p. 118curved or bulging outward
Gauricus has broad inner walls, peppered with craters of various sizes, and it has a rather smooth, slightly convex floor, with no trace of a central uplift.
The Moon and How to Observe It — PDF p. 187Mersenius (84 km), on the western shore of Mare Humorum, is a prominent crater with a broad, terraced wall surrounding a smooth and markedly convex floor.
The Moon and How to Observe It — PDF p. 200extremely complex, intricate, or folded
The unique chemical makeup of KREEP enables it to be used as a chemical tracer to chart the convoluted history of lunar volcanism and asteroidal bombardment.
The Moon and How to Observe It — PDF p. 19KREEP is made up of Potassium (chemical symbol K), rare earth elements (REE) and phosphorus (P), and its unique chemical makeup allows it to be used as a marker for tracing the convoluted history of the Moon’s surface.
The Moon and How to Observe It — PDF p. 20a luminous region around a celestial body, especially the Sun's outer atmosphere
A bright, pearly white region, the lunar corona, can often be seen around the Moon.
The Moon and How to Observe It — PDF p. 63Unlike the solar corona, which is part of the Sun’s atmosphere, the lunar corona is simply caused by the reflection and diffraction of moonlight amid water droplets in the Earth’s lower clouds.
The Moon and How to Observe It — PDF p. 63an optical element designed to reduce aberration or distortion
Light enters the top of the telescope tube through a large corrector plate, a sheet of flat-looking glass with a large secondary mirror mounted at its center.
The Moon and How to Observe It — PDF p. 249The corrector plate is actually aspherical in shape, figured to refract the light onto an internal primary mirror, which reflects light onto the convex secondary mirror, which in turn reflects light back down the tube and through a central hole in the primary mirror into the eyepiece.
The Moon and How to Observe It — PDF p. 249to establish or recognize a relationship between things
At first, the observer, armed with a map, may struggle to correlate the view through the telescope with the major features marked on a map.
The Moon and How to Observe It — PDF p. 83as a result of or provided by something
At the push of a button they deliver sharp, vibration-free views courtesy of moving optical elements (most of them require batteries).
The Moon and How to Observe It — PDF p. 242to hold or support gently, or a supporting frame in which something rests
This spectacle – one of the prettiest sights visible without optical aid – is sometimes called “the old Moon cradled in the young Moon’s arms. ”Viewed from the near side of the Moon at this phase, the Earth would appear as a brilliant, near-full disc.
The Moon and How to Observe It — PDF p. 60The simplest form of mount is a telescope inserted into a large ball that can freely and smoothly rotate in a cradle; several small reflectors are mounted in such a manner, and they are great fun to use.
The Moon and How to Observe It — PDF p. 254a bowl-shaped depression formed by an impact or by volcanic activity
A micrometeoroid that would burn up completely in the Earth’s atmosphere will hit the lunar surface and produce a tiny impact crater.
The Moon and How to Observe It — PDF p. 29As the crust decompresses, rebound effects produce a central uplift in larger craters, and a substantial layer of melted rock accumulates within the crater’s bowl.
The Moon and How to Observe It — PDF p. 30a very small crater
Low, rounded hills called “domes” – typically a few hundred meters high and with bases several kilometers across – are the remnants of ancient lunar volcanoes, and their tiny summit craterlets represent volcanic vents.
The Moon and How to Observe It — PDF p. 38An unusual, unnamed feature just north of the crater Hyginus appears as an ill-defined crater, 20 km in diameter, with a domed floor and a central craterlet.
The Moon and How to Observe It — PDF p. 137believable and worthy of trust
For an LTP observation to be credible, it should be confirmed by experienced observers or, even better, by separate and independent observers.
Atlas of the Moon — PDF p. 109For an observation to be credible, it is vital to have at least two independent observers, one (or both) of them recording with a video camera.
Atlas of the Moon — PDF p. 109a curved shape or phase narrower than a semicircle
However, libration can cause Ptolemaeus to appear on the morning terminator of a distinctly crescent Moon, as well as on a considerably gibbous Moon.
The Moon and How to Observe It — PDF p. 59Earthshine is most obvious when the Moon is a thin waxing or waning crescent in a reasonably dark sky.
The Moon and How to Observe It — PDF p. 60sharply defined and clear
Orthoscopic and Plössl eyepieces deliver crisp images with flat fields of view.
The Moon and How to Observe It — PDF p. 98Despite having narrow apparent fields of view of around 30°, monocentrics deliver excellent, crisp, color-free, high-contrast images of the Moon, completely free from ghost images, and they can be used with low-focal-length telescopes.
The Moon and How to Observe It — PDF p. 252simple, rough, and not carefully refined
This crude trick simply makes a poor image appear slightly less poor, and the presence of the stop reduces the aperture of the instrument, as well as light grasp and resolving power.
The Moon and How to Observe It — PDF p. 246the outermost solid layer of a planet, moon, or other rocky body
As the Moon raises tidal bulges in the Earth’s oceans, friction between the ocean masses and the Earth’s crust acts like a brake, gradually decelerating the Earth’s rate of spin.
The Moon and How to Observe It — PDF p. 13It is thought that the Moon’s differentiated crust and mantle may have formed by about 4.4 billion years ago, only a couple of hundred million years after the Moon’s formation.
The Moon and How to Observe It — PDF p. 18relating to the crust of a planet or moon
Mascons were formed during the excavation of the nearside impact basins, when vast quantities of lunar crustal material were removed, leading to an immediate uplift of denser rocks from the Moon’s mantle.
The Moon and How to Observe It — PDF p. 23Because there has been no lunar tectonic activity or large-scale crustal movement, metamorphic rocks such as schist and gneiss, formed slowly through crustal pressure and heat, are not found on the Moon.
The Moon and How to Observe It — PDF p. 25having an ordered crystal structure or resembling crystal
Thermoluminescence is caused when certain crystalline materials emit light when they are heated (as excited electrons fall back to their ground state), but the amount of light given off by lunar thermoluminescence is entirely incapable of being detected by amateur instruments, and the process certainly would not explain any reported TLP.
The Moon and How to Observe It — PDF p. 45A transparent membrane at the front of the eye, the cornea; focuses light rays through the aqueous humor, a chamber filled with transparent fluid, through an opening in the iris, the pupil, and on through a clear crystalline lens behind it.
The Moon and How to Observe It — PDF p. 239to reach the highest point in the sky or a final peak
Are the rays brightest at full Moon, or are they at maximum brightness when the Sun has culminated at their location?
The Moon and How to Observe It — PDF p. 123From Melbourne (37.5°S), the Moon culminates at an altitude of 24.5°.
The Moon and How to Observe It — PDF p. 53the point at which a celestial body reaches its greatest altitude
When the full Moon is positioned near the extreme southerly point of its orbit, it barely clears the southern horizon at its culmination around midnight in June, when viewed from northern temperate latitudes.
The Moon and How to Observe It — PDF p. 53This graph represents the varying altitude of the Moon in its four main phases at southern culmination from northern temperate regions.
The Moon and How to Observe It — PDF p. 61quick and not detailed or thorough
Even a cursory telescopic view will convince the observer that Copernicus’s floor is considerably depressed beneath the mean level of the surrounding landscape.
The Moon and How to Observe It — PDF p. 160They can be carried in a coat pocket and are great for cursory lunar observation.
The Moon and How to Observe It — PDF p. 246the degree or state of being curved
Prone to the optical aberrations of astigmatism and field curvature, most Cassegrains are large, observatory-sized instruments with focal lengths ranging from f/15 to f/25 – excellent for lunar studies at high-magnification.
The Moon and How to Observe It — PDF p. 248Importantly, a correction factor needs to be introduced into the equation to account for the curvature of the Moon’s surface since the further a feature is in longitude from the mean center of the Moon’s disc, the shorter a shadow of given length will appear to be.
The Moon and How to Observe It — PDF p. 238a room with controlled light for processing or manipulating photographs
Digital images are infinitely easier to enhance and manipulate than conventional photographs in a photo lab darkroom.
The Moon and How to Observe It — PDF p. 99to overwhelm the sight with intense brightness
However, along the terminator the Moon’s surface varies in brightness from pitch black, through all shades of gray, to dazzling white.
The Moon and How to Observe It — PDF p. 86scattered fragments left by destruction, impact, or erosion
The Moon formed from a cloud of debris in orbit around the embryonic Earth.
The Moon and How to Observe It — PDF p. 13Co-accretion According to the theory of co-accretion, around 4.6 billion years ago, the Moon condensed from a primordial cloud of gas, dust and assorted debris in orbit around the Earth.
The Moon and How to Observe It — PDF p. 14angular distance north or south of the celestial equator
Half an orbit later, the Moon attains its most northerly declination, on the border of Gemini and Taurus.
The Moon and How to Observe It — PDF p. 53The declination of the celestial equator is 0°, of the north celestial pole +90°, and of the south celestial pole −90°.
Atlas of the Moon — PDF p. 111to devote something to a particular purpose or activity
Digicams, digital camcorders, webcams and dedicated astronomical CCD cameras have afforded amateur astronomers with quite modest equipment the opportunity to obtain wonderfully detailed images of the Moon.
The Moon and How to Observe It — PDF p. 99Dedicated searches have been made with large professional telescopes as well.
The Moon and How to Observe It — PDF p. 67to reach a conclusion by reasoning from known facts
Traced backwards in time, it can be deduced that several billion years ago the Moon orbited just a few tens of thousands of kilometers away from the Earth, and a terrestrial day matched a lunar “month” of just a few hours; the Moon would have loomed apparently motionless over one hemisphere of the Earth, a great, hot orb that produced solar and lunar eclipses every few hours.
The Moon and How to Observe It — PDF p. 14to alter a shape through force or pressure
Normal faults are the most commonly observed types of fault on the Moon, and result from crustal tension; as the crust is pulled apart, the rocks may deform to a certain degree, but there comes a point when the crust cracks.
The Moon and How to Observe It — PDF p. 41a process of deterioration or loss of normal function
The development of cataracts and age-related macular degeneration (AMD) is inhibited by Vitamin E, a substance found in wheat germ oil, sunflower seed and oil, hazelnuts, almonds, wheat germ, fortified cereals and peanut butter.
The Moon and How to Observe It — PDF p. 240a decline in quality, clarity, or condition
This has implications for observing the Moon, especially from temperate locations: the higher the Moon is in a dark sky, the better the view through the telescope because of increased contrast and less trouble from atmospheric degradation of the lunar image.
The Moon and How to Observe It — PDF p. 61While an image of the Moon taken through, say, a 500mm telephoto lens in conjunction with a ×2 teleconverter will be the same size as one taken through a regular 1,000mm telephoto lens, the teleconverter image may be slightly dimmer and less well resolved, as a slight degree of optical degradation is introduced when the light passes through the extra lenses of the teleconverter.
The Moon and How to Observe It — PDF p. 96to reduce in quality, clarity, or physical condition
When digital zoom comes into play at high magnifications, the quality of the image begins to degrade and the advantages of zooming are completely cancelled out.
The Moon and How to Observe It — PDF p. 100to mark, describe, or show the boundary or outline of something
Dashed lines can be used to delineate features like rays, and dotted lines can be used to mark the boundaries of areas of different tone.
The Moon and How to Observe It — PDF p. 85If a part of the drawing depicts mountainous terrain, attempt to delineate the borders of the terrain, outlining the main peaks, features of relief and main shadows.
The Moon and How to Observe It — PDF p. 85to mislead into believing something false
One thing is important for the user: when one examines a drawing or photograph of the Moon’s relief, the direction of solar illumination has to be taken into account, otherwise the eye can be deluded into accepting optical reversals.
Atlas of the Moon — PDF p. 11to indicate, represent, or mean
The power of binoculars is identified by two figures that denote their magnification and the size of their objective lenses: 7 × 30 binoculars give a magnification of 7 × and have 30mm objective lenses.
The Moon and How to Observe It — PDF p. 241to represent something in a picture, diagram, or words
If a part of the drawing depicts mountainous terrain, attempt to delineate the borders of the terrain, outlining the main peaks, features of relief and main shadows.
The Moon and How to Observe It — PDF p. 85Try to avoid depicting lunar mountains as upturned V shapes – this might be fine for cartoon strips, but it only serves to confuse the appearance of a lunar observational drawing.
The Moon and How to Observe It — PDF p. 85to reduce the amount or supply of something
Taken as a whole, the Moon possesses substantially less iron than the Earth; its rocks contain no water and they are depleted in other volatiles (substances that vaporize at relatively low temperatures).
The Moon and How to Observe It — PDF p. 12the laying down or accumulation of material
Lunar domes are squat features that were built up by lava and ash deposition when the moon was volcanically active.
The Moon and How to Observe It — PDF p. 39This impressively sculpted terrain, formed by the erosion and deposition of piles of debris ejected during the Orientale impact, superficially resembles a terrestrial mountainous landscape that has experienced erosion by an ice sheet.
The Moon and How to Observe It — PDF p. 43to mark, name, or identify for a particular purpose
Partial lunar eclipses are designated a magnitude value from 0 to 1 for their maximum phase; for example, if the magnitude is 0.5, then half of the Moon’s diameter is covered by the umbra at maximum eclipse.
The Moon and How to Observe It — PDF p. 65So, in addition to designating the viewing with a letter and a figure (AI to AV or P1 to P10), a brief, written description of viewing, such as “AII – Good with occasional moments of excellent sight,” can be made.
The Moon and How to Observe It — PDF p. 89an official name, label, or identifying description
If the feature that was observed cannot be identified with an official IAU designation, note its location in relation to several of the nearest named features – “small group of hills in Mare Frigoris, immediately west of Harpalus, ” for example.
The Moon and How to Observe It — PDF p. 88empty, bleak, and without signs of life
Those who claim that any telescope with an aperture smaller than 75mm is useless for lunar observation misunderstand the main reason why most people observe the Moon – for the sheer pleasure of scanning their eyes along the rugged lunar terminator, to be enthralled by the magnificent desolate expanses of the marial plains and to be astounded by the grandeur of our sister planet.
The Moon and How to Observe It — PDF p. 246causing harm or damage
Smoking is detrimental to astronomical observation, let alone the smoker’s general health.
The Moon and How to Observe It — PDF p. 240to destroy or damage severely
Around 65 million years ago, dinosaurs of the late Cretaceous period may have witnessed a significant asteroidal impact that devastated the (now) Yucatan peninsula area.
The Moon and How to Observe It — PDF p. 73a departure from an expected path, value, or condition
However, in practice there can be deviations of up to three-quarters of a day to take into account.
Atlas of the Moon — PDF p. 100entirely lacking something
On the whole, the area of Lacus Excellentiae is monotonous, devoid of obvious faulting or features constructed on a grand scale.
The Moon and How to Observe It — PDF p. 204Ammonius (9 km), a young, bowl-shaped impact crater on Ptolemaeus’s northeastern floor, shows up as a brilliant white spot under a lunar midday Sun, but its surroundings are surprisingly devoid of any prominent ejecta.
The Moon and How to Observe It — PDF p. 207joining nonadjacent corners or slanting across a shape
The most widely available eyepieces have a barrel diameter of 1.25 inches, and these can be mounted to a .965-inch eyepiece tube using an adapter or a hybrid star diagonal (a mirror that flips the image 90°).
The Moon and How to Observe It — PDF p. 247to recognize or show a difference between things
The eye is capable of differentiating between hundreds of shades of gray, so a skilled observer can easily subdivide the basic scale yet further.
The Moon and How to Observe It — PDF p. 86the process by which materials separate according to physical or chemical properties
In the resulting global ocean of molten rock, chemical differentiation would have taken place, causing heavier elements to sink toward the Moon’s center and lighter ones to float to the surface.
Atlas of the Moon — PDF p. 11the spreading or bending of waves around an obstacle or through an opening
One or two (rarely, three) rainbowcolored halos are sometimes observed to encircle the Moon; this is caused by the diffraction of moonlight by ice crystals in the Earth’s upper atmosphere.
The Moon and How to Observe It — PDF p. 63Unlike the solar corona, which is part of the Sun’s atmosphere, the lunar corona is simply caused by the reflection and diffraction of moonlight amid water droplets in the Earth’s lower clouds.
The Moon and How to Observe It — PDF p. 63spread over a wide area without a sharp boundary
Sometimes the lunar halo may be host to parselene, diffuse images of the Moon located 22° from either side of it, caused by moonlight’s refraction among ice crystals in Earth’s upper atmosphere.
The Moon and How to Observe It — PDF p. 63Observations of diffuse glows on the lunar horizon near the terminator, made from lunar orbit, plus amateur observations of the “graying” of normally intensely black shadow near the Moon’s terminator, may indicate the presence of transient dust clouds suspended above the lunar surface.
The Moon and How to Observe It — PDF p. 49a compact digital camera
As a general rule, the digicam with the highest pixel rating will produce the clearest, highest-resolution views of the Moon.
The Moon and How to Observe It — PDF p. 99CCDs in low-end digicams may have an array of 640 × 480 pixels, while a more expensive digicam CCD may boast 2240 × 1680 pixels (around 4 megapixels).
The Moon and How to Observe It — PDF p. 99to make something weaker or less concentrated
Similarly, the rays that form the inner cone, in which the light of the Sun is reduced, let us imagine, as if a large glass prism bends the light passing through it, so that the dark umbral shadow is diluted.
Atlas of the Moon — PDF p. 110to become or make smaller, weaker, or less distinct
Having been formed by very runny lava, the channels always progress downhill, gradually diminishing in depth and width, although the overall slope of the landscape is not always evident.
The Moon and How to Observe It — PDF p. 40An arc of individual craters of diminishing size proceeds from Rutherford westwards across Clavius’s floor: Clavius D (28 km), Clavius C (22 km), Clavius N (13 km), Clavius J (11 km) and Clavius JA (8 km).
The Moon and How to Observe It — PDF p. 191to perceive or distinguish something that is difficult to see
The giant (2,500-km-diameter) South Pole–Aitken Basin can be easily discerned on the lunar far side.
The Moon and How to Observe It — PDF p. 30Dorsa are the same color as the terrain around them, and they cannot be discerned under a high Sun.
The Moon and How to Observe It — PDF p. 39an inconsistency or unexplained difference between things
The task of restoring order to this accumulated mass of discrepancies and coming up with an acceptable nomenclature was taken on by the International Astronomical Union.
Atlas of the Moon — PDF p. 12to spread or scatter in different directions
Moreover, it is known that such insubstantial features, should they ever exist, would not remain for very long – the material would disperse into space just as quickly as it had accumulated.
The Moon and How to Observe It — PDF p. 67to move something from its usual or original position
The additional gravitational attraction of this displaced tidal bulge actually tugs on the Moon and imparts angular momentum to it.
The Moon and How to Observe It — PDF p. 54Libration in latitude, as this phenomenon is called, displaces the mean center of the Moon north–south by between 6.5° and 6.9°.
The Moon and How to Observe It — PDF p. 57a change in position from a reference point
Another consequence of the friction between the Earth’s crust and the oceans is the displacement of the tidal bulge slightly forward of the direction of the Moon.
The Moon and How to Observe It — PDF p. 54Twice every anomalistic month (the lunar month from perigee to perigee), libration in longitude creates a maximum east–west displacement on opposite sides of the Moon’s edge.
The Moon and How to Observe It — PDF p. 57to ignore or pay no attention to
If this is the case, you have my permission to disregard everything your art teacher ever told you!
The Moon and How to Observe It — PDF p. 84to alter the shape or appearance of something inaccurately
Its neighbor, Messier A, measures 13 × 11 km, and has a more distorted shape owing to an extended (nearly double) western rim.
The Moon and How to Observe It — PDF p. 48The airy pattern, an artifact introduced by optics, will distort according to the degree of atmospheric turbulence along its light path.
The Moon and How to Observe It — PDF p. 89an alteration that makes an image, shape, or measurement inaccurate
Apochromatic refractors use special glass in their 2- or 3-element objective lenses to bring the light to a tack-sharp focus, delivering images that are virtually free from the effects of chromatic distortion.
The Moon and How to Observe It — PDF p. 247Views of the Moon through an apochromat are almost completely free of distortion and are of high contrast, rivaling the kind of view to be had through a good-quality long-focal-length Newtonian reflector (see below).
The Moon and How to Observe It — PDF p. 247occurring daily or relating to a daily cycle
Diurnal libration can appear something like the parallax effect produced by an alternate left- and right-eye views of a tennis ball placed 10 m away.
The Moon and How to Observe It — PDF p. 57The extent of this diurnal libration depends on the observer’s actual location on the Earth, and is restricted by the Earth’s apparent diameter of some 2° as seen from the Moon.
The Moon and How to Observe It — PDF p. 57a beneficial result or return from effort
Both these techniques require proficiency in brushwork, and although a description of the methods involved is beyond this book, practice, experimentation and perseverance will pay big dividends.
The Moon and How to Observe It — PDF p. 87a low, rounded swelling of the surface, often of volcanic origin
Even with such fluid lunar lava flows, domes built up when a balance had been struck between the supply of lava being erupted and the rate of cooling of the extruded material.
The Moon and How to Observe It — PDF p. 38Low, rounded hills called “domes” – typically a few hundred meters high and with bases several kilometers across – are the remnants of ancient lunar volcanoes, and their tiny summit craterlets represent volcanic vents.
The Moon and How to Observe It — PDF p. 38the plural of dorsum, used for systems of wrinkle ridges
Dorsa are the same color as the terrain around them, and they cannot be discerned under a high Sun.
The Moon and How to Observe It — PDF p. 39Many of the major dorsa appear to follow the outlines of the mare basins.
The Moon and How to Observe It — PDF p. 39a named wrinkle ridge on a planetary surface
Near the western shore of Mare Serenitatis are a number of narrower dorsa, including Dorsum Buckland (150 km long), Dorsum Gast (60 km long), Dorsum Owen (50 km long) and Dorsum von Cotta (220 km long).
The Moon and How to Observe It — PDF p. 133North of Dorsum Owen, 100 km from the western shore, is a bright circular patch 10 km wide that surrounds a tiny 2.4-km-diameter crater called Linné.
The Moon and How to Observe It — PDF p. 133a pair of optical lens elements used together
Orthoscopic eyepieces comprise four elements, an achromatic doublet eye lens and a cemented triplet field lens.
The Moon and How to Observe It — PDF p. 252Similar to the Ramsdens, their eye lens (the lens closest the eye) consists of an achromatic doublet.
The Moon and How to Observe It — PDF p. 252a disadvantage or negative feature
Photographs taken with slower film can withstand much more enlargement than those taken with faster film, but slow films also have the drawback of requiring more time to expose.
The Moon and How to Observe It — PDF p. 96On the face of it, such an instrument would be ideal for general lunar observation, but there are drawbacks.
The Moon and How to Observe It — PDF p. 242able to deform or flow without breaking
Basaltic in composition, the marial lava flows had the viscosity of motor oil and were ductile and fast-moving.
The Moon and How to Observe It — PDF p. 20to make an exact or corresponding copy
The totally disoriented observer could consider duplicating the atlas pages left-right reversed (or an even more hopeless idea) reading the maps reflected in a hand-held mirror.
Atlas of the Moon — PDF p. 108somewhat dark or dim in color or light
Mare Acidalium is the most prominent of the far-northern hemisphere’s dusky tracts.
The Moon and How to Observe It — PDF p. 74Several dusky bands of lower albedo mark the inner western wall; these shadow bands are a source of fascination to many lunar observers.
The Moon and How to Observe It — PDF p. 171to make something appear very small by comparison
There are several physically larger satellites than the Moon – namely, Saturn’s satellite Titan (5,150km) and Jupiter’s satellites Io (3,630km), Ganymede (5,268km) and Callisto (4,806km) – but they themselves are utterly dwarfed by the giant planets they orbit.
The Moon and How to Observe It — PDF p. 12Comparable lunar valleys, like Vallis Alpes and Vallis Schrödinger, are dwarfed in comparison.
The Moon and How to Observe It — PDF p. 74a mechanism or process that generates a magnetic field from moving conductive material
Studies of remnant magnetism frozen into ancient lunar rocks as they solidified show that the lunar magnetic field strength in the past was at least 3,000 nT and was likely to have been produced in the hot molten interior by a dynamo effect similar to that which produces the Earth’s magnetic field.
The Moon and How to Observe It — PDF p. 22sunlight reflected from Earth that faintly lights the Moon's night side
Some of the Moon’s brighter albedo features are noticeable even when they are not directly illuminated by the Sun, but instead bathed in the glow of earthshine.
The Moon and How to Observe It — PDF p. 45Earthshine How could a spectroscope that is pointed directly towards the surface of the lifeless Moon possibly detect water, molecular oxygen and chlorophyll, the latter indicating the presence of land plants?
The Moon and How to Observe It — PDF p. 60not circular or not centered on the expected focus
In the capture scenario, gravitational perturbations caused the orbit of an inner planet to become so eccentric that it came within the range of capture by the Earth.
The Moon and How to Observe It — PDF p. 16An exceptionally close encounter between Mercury and the Moon may have been sufficient to have both perturbed Mercury into its current eccentric orbit and propelled the Moon across the gulf of space into the Earth’s gravitational embrace.
The Moon and How to Observe It — PDF p. 16a measure of how much an orbit or ellipse departs from a circle
This periodic gravitational tugging is a phenomenon known as evection, and causes the eccentricity of the Moon’s orbit to vary between 0.0432 and 0.0666, a complete cycle recurring every 87.1 years.
The Moon and How to Observe It — PDF p. 55Careful measurement will reveal that the figure is really an ellipse with a mean eccentricity of 0.055 (the ratio of the difference between the major and minor axes to the major axis), with the Earth lying slightly to one side of the center, positioned over a focus of that ellipse.
The Moon and How to Observe It — PDF p. 51an obscuring of one celestial body by another body or its shadow
In an astronomical sense, the recession of the line of nodes is important, since solar and lunar eclipses are dependent on the nodes’ position in relation to the Sun and the Earth.
The Moon and How to Observe It — PDF p. 53The recession of the line of nodes has important consequences for the timing of solar and lunar eclipses.
The Moon and How to Observe It — PDF p. 55the plane of Earth's orbit and the apparent annual path of the Sun on the sky
They must account for our satellite’s relatively large size and explain why it has a near-circular orbit inclined by 5° to the Earth’s orbital plane (the ecliptic).
The Moon and How to Observe It — PDF p. 12Capture theory may explain why the Moon now orbits the Earth at a 5° inclination to the ecliptic, in addition to accounting for the marked difference in the density and composition of the Earth and Moon.
The Moon and How to Observe It — PDF p. 17to force or throw material out
The material originally nearer the surface is ejected furthest, while deeper bedrock is lobbed shorter distances from the rim.
The Moon and How to Observe It — PDF p. 31Streams of ejected debris can produce lines of craters arrayed radially around their parent crater.
The Moon and How to Observe It — PDF p. 32material expelled from an impact crater or volcanic vent
The excavated material is distributed around the crater in an ejecta blanket.
The Moon and How to Observe It — PDF p. 30A plume of ejecta is thrown up from the Moon’s surface as the edge of the explosion cavity is deformed and uplifted.
The Moon and How to Observe It — PDF p. 31a more detailed development or explanation of an idea
One elaboration of the theory suggests that the roughly circular basin of the Pacific Ocean represents the scar of the Moon’s violent birth, the Atlantic Ocean having been a split in the thin terrestrial crust to accommodate the huge mass of material torn from the other side of the planet: hence the matching Atlantic coastlines of Africa and South America.
The Moon and How to Observe It — PDF p. 14to pass, especially of time
Many observers choose to note the time elapsed from that lunation’s new Moon in days and hours to the time of the observation.
The Moon and How to Observe It — PDF p. 90The cable release is pressed while the card is held in front of the lens, and a few seconds are allowed to elapse before the card is quickly withdrawn from the lens and then moved back again, say, a second later.
The Moon and How to Observe It — PDF p. 97able to return to an original shape after being deformed
The types of seismic waves detected include pressure waves and shear elastic waves which cannot travel through fluid, proving that the waves, had passed through a solid mantle.
The Moon and How to Observe It — PDF p. 21a closed oval curve with two focal points
An ellipse is a closed curve with two focal points lying on its main axis; the Earth lies at one focal point of the Moon’s orbital ellipse.
The Moon and How to Observe It — PDF p. 51Perturbations by the Sun’s gravity compel the Moon’s orbital ellipse to rotate slowly in space.
The Moon and How to Observe It — PDF p. 54the angular separation of a celestial body from the Sun as seen by an observer
It varies in apparent brightness by 1.7 magnitudes at either side of elongation since half of its surface has better reflectivity than the other.
The Moon and How to Observe It — PDF p. 78For example, the first quarter Moon has an eastern elongation of 90°.
The Moon and How to Observe It — PDF p. 260difficult to find, observe, or define
Vallis Schrödinger is one of the most elusive features on the Moon, requiring a very favorable libration and evening illumination (just after full Moon) to discern.
The Moon and How to Observe It — PDF p. 231to come or spread outward from a source
The dark material from which many of the dark areas are composed is often found to emanate from small craters, and is blown by the Martian winds across local surfaces.
The Moon and How to Observe It — PDF p. 74Such extensive radial impact structure emanates from the Orientale impact basin, and it is clearly visible in and around many features of the Moon’s southwestern limb.
The Moon and How to Observe It — PDF p. 205to fix or enclose firmly within surrounding material
Typical breccias contain coarse fragments embedded in a fine-grained crystal matrix.
The Moon and How to Observe It — PDF p. 26For example, the base of Hadley Rill, a large lunar canyon on the eastern border of Mare Imbrium, is covered with a thick blanket of soil embedded with sizable boulders that have fallen from the higher slopes.
The Moon and How to Observe It — PDF p. 49at a very early stage of development
The Moon formed from a cloud of debris in orbit around the embryonic Earth.
The Moon and How to Observe It — PDF p. 13The formation of the Moon is now widely thought to have been the result of a gigantic Mars-sized planetary impact with the embryonic Earth.
The Moon and How to Observe It — PDF p. 17a light-sensitive photographic coating or a mixture of immiscible liquids
In this, the telescopic lunar image passes through the open camera shutter and falls onto the photographic emulsion.
Atlas of the Moon — PDF p. 108to surround or contain within a boundary
The horns of the crescent in the northeast enclose an area of lower ground.
The Moon and How to Observe It — PDF p. 177Under a high illumination, all traces of radial impact structure disappear, Theophilus’ rim appearing as a ghostly gray ring enclosing the brilliant spots of its central peaks and Theophilus B.
The Moon and How to Observe It — PDF p. 213a serious or sustained effort
As a result of the joint endeavors of many generations of selenographers, a unique pantheon has come into existence on the Moon.
Atlas of the Moon — PDF p. 12originating from processes within a planet or moon
Almost all the large craters visible on the Moon have been formed by asteroidal impact, but a few smaller craters are endogenic, of volcanic origin.
The Moon and How to Observe It — PDF p. 259Lunar volcanoes and faults are endogenic.
The Moon and How to Observe It — PDF p. 261to involve something as a necessary part or consequence
Digital cameras are particularly well suited to this method and the experimentation that lunar photography entails.
Atlas of the Moon — PDF p. 109something regarded as a distinct and independent whole
The original Humorum multiring impact basin was a much more extensive entity, but most traces of its outer rings have been obliterated by subsequent impacts and flooding by lava.
The Moon and How to Observe It — PDF p. 198the surrounding area or nearby region
Copernicus and its environs are thrilling to observe, and the bright rays that spread in all directions from it can be resolved into a complex series of radial rays that extend in all directions for more than 800 km over the surrounding regions.
The Moon and How to Observe It — PDF p. 121Area Ten This crater-crowded area of the southern lunar uplands south of Mare Nubium to the limb is dominated by several very large craters: Deslandres in the northeast, Clavius in the south and Bailly near the southwestern limb (the south polar region and its environs are described in Area Thirteen).
The Moon and How to Observe It — PDF p. 186tables giving predicted positions or events for celestial bodies
The Sun’s selenographic colongitude is numerically equal to the selenographic longitude of the morning terminator; the figure is published in astronomical ephemerides and can be displayed on many lunar computer programs.
The Moon and How to Observe It — PDF p. 91a table of predicted positions or events for a celestial body over time
Tables of colongitude in an ephemeris are consulted in order to plan or research lunar observations.
The Moon and How to Observe It — PDF p. 259a distinct period of time marked by particular events or conditions
The Soviet probe Luna 3 heralded a new epoch of global cartography, when it photographed a part of the far side in October 1959, and during the American Lunar Orbiter program in 1966–67 the whole sphere was surveyed, with the exception of less than 1 percent of the south polar region.
Atlas of the Moon — PDF p. 11to regard as equal or correspond in value or effect
This explains why the density of the Moon equates with that of the Earth’s mantle, and why the Moon lacks a sizable iron core.
The Moon and How to Observe It — PDF p. 18For example, at a magnification of 50 ×, an apparent field of 50° will equate to a true field of view of 1°, and the Moon will move from one edge of the field to the other in just 2 minutes.
The Moon and How to Observe It — PDF p. 242a mathematical statement that two expressions are equal
This requires the exact scale of the image to be known and usually involves incorporating the Moon’s apparent angular diameter at the time of the image into the equation.
The Moon and How to Observe It — PDF p. 238Importantly, a correction factor needs to be introduced into the equation to account for the curvature of the Moon’s surface since the further a feature is in longitude from the mean center of the Moon’s disc, the shorter a shadow of given length will appear to be.
The Moon and How to Observe It — PDF p. 238the great circle midway between a body's rotational poles
At the Moon’s equator, the Sun takes about an hour to set, and this produces a gradient of illumination at the terminator.
The Moon and How to Observe It — PDF p. 62If the Moon’s orbit were circular and the plane happened to coincide with the celestial equator, all retardations would be around the same length.
The Moon and How to Observe It — PDF p. 62relating to an equator or aligned with the celestial equator
Because the inner regions of the protoplanet became more massive, there was a gradual acceleration in its axial rotation, and centrifugal forces gave rise a pronounced equatorial bulge.
The Moon and How to Observe It — PDF p. 13Highmagnification shots of the lunar surface made using slow film require that the camera be attached to a telephoto lens or telescope on a driven equatorial drive.
The Moon and How to Observe It — PDF p. 96either annual time when the Sun crosses the celestial equator and day and night are nearly equal
The ‘Harvest Moon’ is the full Moon nearest to the date of autumnal equinox on 23 September.
The Moon and How to Observe It — PDF p. 109The Harvest Moon is the full Moon nearest the date of autumnal equinox on 23 September, and was so named because farmers were able go about their agricultural business from dusk to dawn assisted by a bright Moon that made its appearance only slightly later each evening.
The Moon and How to Observe It — PDF p. 63to wear away material gradually through physical or chemical processes
Wearing down solid rock, the continual rain of meteoroids has served to erode the Moon’s surface, smoothing mountain peaks that were once as sharp and jagged as their terrestrial counterparts.
The Moon and How to Observe It — PDF p. 29The oldest is composed of highly eroded ancient craters and basins, interspersed with younger cratered areas, smooth plains, hummocky plains, ridges, escarpments and fractures.
The Moon and How to Observe It — PDF p. 69the gradual wearing away or alteration of a surface
The Copernican Period now shows the effects of surface erosion by innumerable meteoroids and micrometeoroids – a relentless pummeling that has gradually rounded the lunar hills and produced a layer of fine soil.
The Moon and How to Observe It — PDF p. 21Erosion by meteoroids gradually churned up the ray material on the surface, fading it over time.
The Moon and How to Observe It — PDF p. 36causing or relating to gradual wearing away
Vallis Schröteri, cut by the erosive action of fast-moving lava flows, is one of the more obvious signs of volcanic activity in this region of the Moon.
The Moon and How to Observe It — PDF p. 172While the Grand Canyon has been hewn out of the Earth’s crust by the continuous erosive action of the Colorado river over hundreds of thousands of years, erosion is not the cause of its lunar counterpart: there never have been appreciable quantities of running liquid water on the Moon’s surface.
The Moon and How to Observe It — PDF p. 125to expel lava or other material, or to emerge through volcanic activity
Different phases of lava flooding are quite evident telescopically, as many maria take on a patchwork appearance that suggests numerous phases of volcanic activity that erupted batches of lavas of slightly different chemical composition.
The Moon and How to Observe It — PDF p. 38The mare lava erupted from about 4 to 3 billion years ago.
The Moon and How to Observe It — PDF p. 37an event in which lava, ash, gas, or other material is expelled from a vent
Intermittent eruptions of volcanic ash and pyroclastic deposits produced steeper-sided volcanic cones.
The Moon and How to Observe It — PDF p. 38Low-viscosity lava, squeezed through very narrow volcanic vents, can produce fire fountains that spray a multitude of tiny droplets – successive eruptions are capable of building up quite steep-sided volcanic cones.
The Moon and How to Observe It — PDF p. 38a long, steep slope or cliff separating areas of different elevation
Crustal tension has caused the crust to crack, and the western block of crust has slipped down, leaving a prominent escarpment some 110 km long.
The Moon and How to Observe It — PDF p. 41The oldest is composed of highly eroded ancient craters and basins, interspersed with younger cratered areas, smooth plains, hummocky plains, ridges, escarpments and fractures.
The Moon and How to Observe It — PDF p. 69to escape or avoid detection
It is possible that much smaller moonlets exist, but they would have to be basketball-sized or smaller to have evaded detection for so long.
The Moon and How to Observe It — PDF p. 67to disappear or diminish gradually
Although fission might explain why the Moon’s core is not as massive as the Earth’s and the similarity in their oxygen isotopes, support for the theory has almost completely evaporated among planetary scientists.
The Moon and How to Observe It — PDF p. 14a periodic variation in the Moon's orbit caused mainly by the Sun's gravitational pull
This periodic gravitational tugging is a phenomenon known as evection, and causes the eccentricity of the Moon’s orbit to vary between 0.0432 and 0.0666, a complete cycle recurring every 87.1 years.
The Moon and How to Observe It — PDF p. 55As a consequence of evection, the Moon can be displaced in longitude by as much as two and a half times its own diameter, a displacement so great that it was observed in ancient times and recognized by Hipparchus.
The Moon and How to Observe It — PDF p. 55to remove material by digging or impact
Other DHCs are produced by impacts that excavate darker material from beneath the lunar surface.
The Moon and How to Observe It — PDF p. 259the removal of material to form a hollow or crater
Mascons were formed during the excavation of the nearside impact basins, when vast quantities of lunar crustal material were removed, leading to an immediate uplift of denser rocks from the Moon’s mantle.
The Moon and How to Observe It — PDF p. 23For example, an intrusive magmatic dike that has been exposed by the crater’s excavation may appear as a distinct, dark line.
The Moon and How to Observe It — PDF p. 234free from a rule, obligation, or restriction
Astronomers’ Observing Guides Series ISSN 1611-7360 ISBN 1-85233-748-6 Springer Science+Business Media springeronline.com © Springer-Verlag London Limited 2005 The use of registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant laws and regulations and therefore free for general use.
The Moon and How to Observe It — PDF p. 5originating outside a planet or moon
Most lunar craters are exogenic.
The Moon and How to Observe It — PDF p. 261unusual, striking, or originating from a distant place
Riccioli discarded most of the names proposed by Hevelius (who had disregarded those of van Langren) and gave the maria exotic names, which are perhaps more romantic than suitable—for example, Mare Imbrium (Sea of Rains), Oceanus Procellarum (Ocean of Storms).
Atlas of the Moon — PDF p. 12Viewing through the eyepiece of a telescope, one can feel like a space traveler admiring the beauty of a distant world, with this atlas serving as a handy travel guide, helping you identify and appreciate various features of the Moon's exotic landscape.
Atlas of the Moon — PDF p. 109a wide and continuous area or extent
Because there was never any substantial lunar atmosphere, and the surface was never covered with any expanses of water, not even the most primitive forms of life developed on the Moon.
The Moon and How to Observe It — PDF p. 24The Moon’s surface does not reflect radio waves as strongly as it would were it covered with large expanses of solid rock, and it was known to be covered in a thick layer of soil long before the first soft-landing probes touched down on its surface.
The Moon and How to Observe It — PDF p. 52an organized journey undertaken for exploration or another specific purpose
It was at the foot of the Apennines, close to Rima Hadley, that the Apollo 15 expedition landed.
Atlas of the Moon — PDF p. 38The Apollo 17 expedition landed in a valley between mountains to the north of Littrow.
Atlas of the Moon — PDF p. 41the process of trying or testing methods to discover what works
Both these techniques require proficiency in brushwork, and although a description of the methods involved is beyond this book, practice, experimentation and perseverance will pay big dividends.
The Moon and How to Observe It — PDF p. 87extremely beautiful, delicate, or finely detailed
Besides, why bother to draw or even image the Moon through a backyard telescope when the entire lunar surface has already been mapped in exquisite detail?
The Moon and How to Observe It — PDF p. 83the complete disappearance of a species or the ending of visibility or light
Current theories about the extinction of many dinosaur species credit this crater with having just the right age, size and location to have been responsible for this catastrophe.
The Moon and How to Observe It — PDF p. 73A special filter wheel called a “crater extinction device” or a calibrated variabledensity filter will enable the brightness of an individual lunar feature to be measured according to the point at which it ceases to be visible. With practice, a feature’s apparent brightness during the lunar day can be ascertained, along with features in the target’s immediate vicinity.
The Moon and How to Observe It — PDF p. 234to remove, obtain, or select something from a larger source
Names and biographical data have been extracted from the respective volumes of the Transactions of the IAU and from reference 4.
Atlas of the Moon — PDF p. 112Later, the sharpest video frames can be selected, extracted as digitized images, stacked, and processed with the appropriate computer software.
Atlas of the Moon — PDF p. 109excessive or unreasonably large
Unfortunately, newspaper advertisements announcing massive stock clearances of telescopes and binoculars are often full of outrageous hyperbole, with claims of extravagant magnifications and the ability of the instrument to show all the wonders of the Universe.
The Moon and How to Observe It — PDF p. 245the roughly spherical part of the eye within the socket
This lens focuses light across a chamber filled with vitreous humor, a clear jelly that gives the eyeball its rigidity, and an upside-down image is projected onto the retina inside the back part of the eyeball.
The Moon and How to Observe It — PDF p. 239the optical element through which an observer views a telescope image
While the terminator in these areas can be traced at low power through the telescope eyepiece, high magnification will reveal a gradual fade from the day to night hemispheres.
The Moon and How to Observe It — PDF p. 62Until the advent of photography in the 19th Century, drawing at the eyepiece was the only means of recording the Moon’s features.
The Moon and How to Observe It — PDF p. 82one of the flat faces or distinct surfaces of an object
The largest peak, just east of center, is a markedly pyramidal structure with faceted sides.
The Moon and How to Observe It — PDF p. 217the hemisphere of the Moon that normally faces away from Earth, or relating to it
Many of the bigger, generally unflooded far-side impact basins display central massifs and a system of concentric mountain rings.
The Moon and How to Observe It — PDF p. 43Far-side features will therefore be brought onto the eastern edge of the Earth-facing hemisphere, and they can be observed if the illumination is right.
The Moon and How to Observe It — PDF p. 56very weak or faint
Triboelectric lightning flashes only occur in high-pressure environments (such as the Earth’s atmosphere); any triboelectric lunar glows would be far too feeble to be discerned from the Earth.
The Moon and How to Observe It — PDF p. 47a common group of rock-forming silicate minerals
The Moon’s bright highland regions – the shattered, impact-battered remnants of its original crust – are made up of rocks rich in the mineral feldspar, and are generally termed “anorthositic” rocks.
The Moon and How to Observe It — PDF p. 26Anorthosites are made up of 90% or more of the mineral plagioclase, a very light-colored form of the mineral feldspar, and crystallized out of the Moon’s early magma “ocean” around 4.5 billion years ago to form the first lunar crust.
The Moon and How to Observe It — PDF p. 26limited in size, amount, or duration
However finite the number of processes that have sculpted each of the Solar System’s worlds, the most surprising fact is that each of them is noticeably different, but few show such variety or are as majestic as our sister planet, the Moon.
The Moon and How to Observe It — PDF p. 80the splitting of something, especially an atomic nucleus or an astronomical body
Fission The fission theory states that the material of the Moon and Earth was once incorporated in a single proto-planet that accreted from material within the solar nebula around 4.6 billion years ago.
The Moon and How to Observe It — PDF p. 13Now disfavored, the fission hypothesis of the formation of the Moon was first proposed in the 19th century.
The Moon and How to Observe It — PDF p. 13a projecting rim or broad outer edge
East of Piton, at the eastern end of the lunar Alps, lies the crater Cassini with its unusual extended outer flange and dark-flooded floor punctuated by two large craters.
The Moon and How to Observe It — PDF p. 116Under morning or evening illumination, a broad flange of impact structuring can be discerned in the crater’s vicinity, this taking the form of a mass of radial ridges that extend from the rim to distances of up to 100 km.
The Moon and How to Observe It — PDF p. 143the side of a mountain, crater, or other raised feature
Dorsa Lister continues to track north, where it meets the flanks of the crater Bessel.
The Moon and How to Observe It — PDF p. 133Archimedes’ interior walls are terraced, and outside its sharp rim there are well-rounded flanks indented with a prominent concentric groove.
The Moon and How to Observe It — PDF p. 148a sudden burst of radiation or brightness
There have been reports of TLP (in the form of localized brightenings) taking place at the same time as the arrival of high-energy solar particles emanating from solar flares.
The Moon and How to Observe It — PDF p. 45to throw or drive something forcefully
It saw the Earth and Moon as having once been joined in a hot rotating body whose rapid spin created centrifugal forces powerful enough to fling off the material of the Moon.
The Moon and How to Observe It — PDF p. 13The impact vaporized the local lunar crust, carving out a 93 km crater and flinging out masses of debris, larger fragments of which produced secondary impact craters and pitting arranged in a radial fashion around Copernicus; traces of this secondary, impact structure can be seen in the extensive radial grooves and ridges surrounding the crater, although much of the finer chain craters cannot be resolved through binoculars and small telescopes.
The Moon and How to Observe It — PDF p. 121to turn or reverse quickly
When the shutter button is pressed, the mirror instantly flips out of the way of the light path, allowing it to project directly onto the film.
The Moon and How to Observe It — PDF p. 95The brain automatically flips the image the right-way-up and processes it.
The Moon and How to Observe It — PDF p. 239relating to a focus or to the point where rays converge
An ellipse is a closed curve with two focal points lying on its main axis; the Earth lies at one focal point of the Moon’s orbital ellipse.
The Moon and How to Observe It — PDF p. 51A tripod-mounted SLR and a telephoto lens with a focal length from 800 to 2,000mm will deliver the best telephoto lunar photographs.
The Moon and How to Observe It — PDF p. 96recorded moving images, especially video material
Camcorders have fixed lenses, and lunar footage must be obtained afocally through the telescope eyepiece.
The Moon and How to Observe It — PDF p. 101The process can be time-consuming – the time spent running through the video footage and processing the images can amount to far longer than the time actually spent taking the footage.
The Moon and How to Observe It — PDF p. 101the apparent compression of a shape viewed at an oblique angle
From our terrestrial vantage point, foreshortening causes its east–west axis to be squashed.
The Moon and How to Observe It — PDF p. 150to lose or give up something as a result of circumstances
In just one decade the Moon had forfeited its remoteness, and lunar research largely shifted from astronomy to geology.
Atlas of the Moon — PDF p. 9to add nutrients to food or make something stronger
The development of cataracts and age-related macular degeneration (AMD) is inhibited by Vitamin E, a substance found in wheat germ oil, sunflower seed and oil, hazelnuts, almonds, wheat germ, fortified cereals and peanut butter.
The Moon and How to Observe It — PDF p. 240a period of two weeks
During a couple of hours at sunrise, the lunar surface heats up from a chilly –170°C to a blisteringly hot 130°C (and vice versa at lunar sunset, a fortnight later) – a range of 300°C.
The Moon and How to Observe It — PDF p. 46the small central area of the retina responsible for sharp detailed vision
At the very center of the retina lies the fovea, the spot with the greatest concentration of cones, allowing high-detail color vision at the center of the field of vision.
The Moon and How to Observe It — PDF p. 239However, in low-light circumstances, for example, when attempting to view dim galaxies, only the rod cells lying around the fovea, away from the center of the field of view, are triggered.
The Moon and How to Observe It — PDF p. 239a crack or break in rock or another solid material, or to cause such a break
Long time delays in the arrival of seismic waves also suggest that the lunar crust is highly fractured and faulted.
The Moon and How to Observe It — PDF p. 21Tethys has an interesting surface, full of impact craters and huge fractures, one of which stretches more than the satellite’s 1,040 km diameter.
The Moon and How to Observe It — PDF p. 78easily broken, damaged, or destroyed
Their courses were later exposed when the fragile tunnel roofs collapsed, and the remnants of the original roof can be observed on the rille floor, some large house-sized fragments having survived the fall intact.
The Moon and How to Observe It — PDF p. 40It is widely accepted that meteor streams are almost exclusively composed of fragile grains of dust blown out by cometary nuclei, and contain nothing of a size large enough to produce any observable effects on the Moon, however brief.
The Moon and How to Observe It — PDF p. 46resistance produced when surfaces or materials move against one another
As the Moon raises tidal bulges in the Earth’s oceans, friction between the ocean masses and the Earth’s crust acts like a brake, gradually decelerating the Earth’s rate of spin.
The Moon and How to Observe It — PDF p. 13Another consequence of the friction between the Earth’s crust and the oceans is the displacement of the tidal bulge slightly forward of the direction of the Moon.
The Moon and How to Observe It — PDF p. 54a narrow border or colored edge, or to surround with such a border
Through a Galilean telescope the Moon is surrounded by fringes of vividly colored light, and the whole image appears washed out and blurry.
The Moon and How to Observe It — PDF p. 246Many budget imported achromatic refractors have focal lengths of f/8 to as short as f/5, and although they do display noticeable chromatic distortion, mainly in the form of a violet fringe around the Moon and the brighter planets, they offer good resolution and good contrast.
The Moon and How to Observe It — PDF p. 247a long, narrow groove or trench in a surface
Somewhat easier to discern is the nearby Rima Bradley (130 km long), which cuts a curving furrow across the hills north of Mons Bradley.
The Moon and How to Observe It — PDF p. 136Rima G Bond cuts a 150 km furrow across the plain and through the hills to the west, visible through a 100mm telescope.
The Moon and How to Observe It — PDF p. 144to join or melt together
Lunar breccias are made up of fused fragments of material derived from impacts.
The Moon and How to Observe It — PDF p. 28incapable of producing a useful result
On nights of poor seeing, when the atmosphere is shimmering and the stars scintillate wildly, attempts to observe the Moon at high-magnification through large instruments can prove futile, as it can take on the appearance of a shimmering, boiling mass, hardly worth bothering to look at.
The Moon and How to Observe It — PDF p. 246a vast gravitationally bound system of stars, gas, dust, and dark matter
However, in low-light circumstances, for example, when attempting to view dim galaxies, only the rod cells lying around the fovea, away from the center of the field of view, are triggered.
The Moon and How to Observe It — PDF p. 239Observers of faint deep sky objects, both professional and amateur, regard the Moon as something of a nuisance, an inconvenient source of light pollution whose glare drowns out the faint light from distant nebulae and galaxies.
The Moon and How to Observe It — PDF p. 82in the state of a gas or composed of gas
It is possible that they were excavated by small, gaseous eruptions immediately after the Stickney impact, when water ice in Phobos’s interior was superheated and exploded onto the surface.
The Moon and How to Observe It — PDF p. 75Two other mechanisms might cause a gaseous lunar eruption to glow.
The Moon and How to Observe It — PDF p. 47a sudden short intake of breath caused by surprise
The observing site is engulfed in darkness as temperatures drop, and a momentary silence is soon broken by gasps of astonishment from its viewers.
The Moon and How to Observe It — PDF p. 65to estimate or measure the amount, size, or condition of something
Prime focus exposure times must be gauged according to the telescope’s focal length, the ISO of the film used and the phase of the Moon.
The Moon and How to Observe It — PDF p. 98The Moon’s phase can also be indicated by a short note, such as “waxing gibbous” or “waning crescent.” A more exact figure used to gauge the Moon’s phase denotes the percentage of the near side that appears illuminated.
The Moon and How to Observe It — PDF p. 90relating to the structure, materials, and history of a planetary body
About 3 billion years ago the Moon's endogenic activity rapidly ceased, and the most active geologic processes came to an end.
Atlas of the Moon — PDF p. 11a scientist who studies rocks, planetary materials, and geological processes
A planetary geologist explains how the large lunar basins were formed.
The Moon and How to Observe It — PDF p. 270relating to the physical properties and processes of a planet or moon
Current geophysical theories do not support this assertion – the Atlantic basin itself is a very young feature, just 130 million years old.
The Moon and How to Observe It — PDF p. 14the study of a planet's physical properties and processes
Founded in 1820, the RAS is the UK’s leading professional body for astronomy and astrophysics, geophysics, solar and solar-terrestrial physics and planetary sciences.
The Moon and How to Observe It — PDF p. 267more than half illuminated but less than full
After full, the Moon “wanes” through gibbous, last quarter, crescent and back to new Moon once more.
The Moon and How to Observe It — PDF p. 61The two bodies’ mutually observable phases are opposites of one another; for example, when the Earth appears full from the Moon, the Moon appears new from the Earth; when the Moon is a waxing crescent, the Earth is in a waning gibbous phase.
The Moon and How to Observe It — PDF p. 60relating to glaciers or moving masses of ice
Many of Ariel’s features, like crustal melts and glacial flows, have no analogy with anything seen on the lunar surface.
The Moon and How to Observe It — PDF p. 79Of course, large glacial ice sheets have never heaved their way across the Moon’s surface; the pattern around Mare Imbrium and other large impact basins was caused by secondary impact sculpting, combined with faulting.
The Moon and How to Observe It — PDF p. 116the covering or reshaping of terrain by glaciers or moving ice
There are areas of very smooth, featureless plains, a strange landscape called “cantaloupe” terrain, and ancient valleys that have undergone glaciation.
The Moon and How to Observe It — PDF p. 79This strange little world, only 480 km in diameter, has had a complex history involving active tectonics, crustal melting and movement, glaciation and asteroidal impact.
The Moon and How to Observe It — PDF p. 79a large, slowly moving mass of ice
Lava flooding within the near-side impact basins has obliterated many of their internal mountain structures, but here and there peaks do rise abruptly above the flat marial plains, an example is like the nunataks, which protrude through the glaciers of Greenland.
The Moon and How to Observe It — PDF p. 43strong or dazzling light that makes seeing difficult
The practical visibility of any satellite of the Moon depends upon the object’s size, its reflective properties (albedo) and its proximity to the Moon’s glare.
The Moon and How to Observe It — PDF p. 68At maximum eclipse, a portion of the Moon remains illuminated by direct sunlight, and the glare it causes makes the eclipsed part of the Moon appear dark and rather colorless.
The Moon and How to Observe It — PDF p. 126having the appearance or physical character of glass
This sample consists of fragments of glass, minerals and rock cemented together in a glassy matrix.
The Moon and How to Observe It — PDF p. 28The dark material is where low-velocity impact melt, composed of dark glassy material, splashed onto the crater’s immediate surroundings.
The Moon and How to Observe It — PDF p. 36to shine with a small or reflected light
In the evening, as Plato’s eastern flanks have begun to be surrounded by the darkness of the terminator, its inner eastern wall gleams as a bright crescent in the rays of the setting Sun as the floor darkens.
The Moon and How to Observe It — PDF p. 166a narrow, steep-sided valley or channel
Earth’s largest land gorge, the Grand Canyon in Arizona, averages 13 km wide and 1,600 m deep.
The Moon and How to Observe It — PDF p. 125Halley (36 km), a flat-floored crater with a tiny central hill, intrudes upon Hipparchus’s southern flanks, and a narrow gorge (82 km long) proceeds south of Halley, passing just east of the prominent crater Albategnius (136 km).
The Moon and How to Observe It — PDF p. 209a block of crust that has dropped between roughly parallel faults
Many prominent graben cut across lunar maria, parallel to mare borders; these are known as arcuate rilles because of their curving paths.
The Moon and How to Observe It — PDF p. 41When a block of crust lying between two parallel normal faults subsides, a feature known as a graben rille results.
The Moon and How to Observe It — PDF p. 41the rate or degree of change in slope, brightness, or another quantity
At the Moon’s equator, the Sun takes about an hour to set, and this produces a gradient of illumination at the terminator.
The Moon and How to Observe It — PDF p. 62At first view, Rupes Recta appears to be an impressively steep wall dividing a 126 km section of the mare, but in reality the scarp face has a gentle gradient of 7°–30° and a height of around 500 m.
The Moon and How to Observe It — PDF p. 41impressive beauty, scale, or magnificence
A high-magnification camcorder sweep along the Moon’s terminator, taken under good viewing conditions and using a well-aligned driven telescope and slow-motion controls, enables the viewer to experience the grandeur of the Moon in a way that viewing still photographs cannot convey.
The Moon and How to Observe It — PDF p. 101Those who claim that any telescope with an aperture smaller than 75mm is useless for lunar observation misunderstand the main reason why most people observe the Moon – for the sheer pleasure of scanning their eyes along the rugged lunar terminator, to be enthralled by the magnificent desolate expanses of the marial plains and to be astounded by the grandeur of our sister planet.
The Moon and How to Observe It — PDF p. 246relating to the force of gravity
Instability within the proto-planet’s rapidly rotating molten mass, produced mainly by the gravitational pull of the Sun, caused it to elongate.
The Moon and How to Observe It — PDF p. 13In the capture scenario, gravitational perturbations caused the orbit of an inner planet to become so eccentric that it came within the range of capture by the Earth.
The Moon and How to Observe It — PDF p. 16to pass very close to or barely touch an edge
Such observations are best made during grazing occultations, when the limb of the Moon just touches the star at maximum occultation and the star appears to graze along at a tangent to the lunar disc.
The Moon and How to Observe It — PDF p. 67The edge of the Moon is quite irregular, and grazing stars can appear to blink on and off several times as they disappear behind hills and mountains and reappear in lunar valleys.
The Moon and How to Observe It — PDF p. 67a network of intersecting lines used for coordinates or measurement
The division between each area described does not follow the exact lines of a grid, as this would contrive to split up the descriptions of some features and associated groups of features between areas.
The Moon and How to Observe It — PDF p. 129The basic grid of selenographic coordinates is illustrated in Fig. 13.
Atlas of the Moon — PDF p. 11a long, narrow depression or channel in a surface
Beyond the rim there is a considerable amount of physical structure, including prominent radial ridges and grooves, in addition to secondary cratering caused by the impact of substantial chunks of excavated bedrock.
The Moon and How to Observe It — PDF p. 32Grooves running across the asteroid’s surface may have resulted from a large impact in the past.
The Moon and How to Observe It — PDF p. 75a ring or zone of light surrounding an object
One or two (rarely, three) rainbowcolored halos are sometimes observed to encircle the Moon; this is caused by the diffraction of moonlight by ice crystals in the Earth’s upper atmosphere.
The Moon and How to Observe It — PDF p. 63Sometimes the lunar halo may be host to parselene, diffuse images of the Moon located 22° from either side of it, caused by moonlight’s refraction among ice crystals in Earth’s upper atmosphere.
The Moon and How to Observe It — PDF p. 63to hinder or make progress difficult
Electrical signal noise greatly hampers the use of webcams to capture faint deep-sky objects like nebulae and galaxies, but the electronic circuitry within some makes of webcam have been modified by some amateurs to take longer exposures with reasonable success.
The Moon and How to Observe It — PDF p. 101a raised area of land or terrain projecting into a sea or plain
The rilles lead across to where Mare Serenitatis’ mountain border resumes, in the form of Montes Haemus, beginning with the crenulated headland of Promontorium Archerusa.
The Moon and How to Observe It — PDF p. 135A large mountainous headland, Promontorium Agarum, projects into Mare Crisium from its southeastern shore.
The Moon and How to Observe It — PDF p. 151to rise, move, or push with great force
Of course, large glacial ice sheets have never heaved their way across the Moon’s surface; the pattern around Mare Imbrium and other large impact basins was caused by secondary impact sculpting, combined with faulting.
The Moon and How to Observe It — PDF p. 116large, heavy, or substantial
A short distance southeast of Montes Teneriffe, the hefty mountain block of Mons Pico (base size 15 × 25 km) rises to a height of 2,400 m above the marial plain.
The Moon and How to Observe It — PDF p. 166Larger computerized telescopes of the SCT varieties produced by Meade and Celestron, for example, are constructed well enough to accommodate hefty accessories.
The Moon and How to Observe It — PDF p. 256one half of a sphere or spherical body
The eastern maria of Tranquillitatis, Crisium and Fecunditatis were extruded around 3.5 billion years ago, preceding the in-filling of Imbrium and Procellarum in the western hemisphere by several hundred million years.
The Moon and How to Observe It — PDF p. 21Note the remarkable difference in the number of large, dark, lava-filled basins between the two lunar hemispheres.
The Moon and How to Observe It — PDF p. 37to signal or mark the beginning of something important
The Soviet probe Luna 3 heralded a new epoch of global cartography, when it photographed a part of the far side in October 1959.
Atlas of the Moon — PDF p. 11cut, shaped, or carved, especially roughly
On the northern shoreline of Mare Frigoris, due north of Plato (see Area Six) is the irregularly shaped, disintegrated crater Birmingham (92 km), a feature with low, roughly hewn walls, identifiable under a low illumination.
The Moon and How to Observe It — PDF p. 141While the Grand Canyon has been hewn out of the Earth’s crust by the continuous erosive action of the Colorado river over hundreds of thousands of years, erosion is not the cause of its lunar counterpart: there never have been appreciable quantities of running liquid water on the Moon’s surface.
The Moon and How to Observe It — PDF p. 125elevated terrain, especially the Moon's bright, heavily cratered regions
Today we find large amounts of anorthosite in the Moon’s highland crust; this is a mineral that forms exclusively in hot molten magma.
The Moon and How to Observe It — PDF p. 18The highland crust is considerably thicker, having an average thickness of 70 km, and in places on the far side has a thickness exceeding 100 km.
The Moon and How to Observe It — PDF p. 23to move quickly from one point or object to another
But, as the major landmarks are noted, they can be used as stepping stones to hop across to other, more subtle, features that may have originally been overlooked.
The Moon and How to Observe It — PDF p. 83Krafft and Cardanus make a prominent landmark that can be used to hop across to the limb to identify a group of large features that occupy the western libration zone.
The Moon and How to Observe It — PDF p. 173to remain suspended or appear to stay in one place
Many lunar observers will freely admit (I certainly do) that they often imagine their telescope eyepiece to be the porthole of their very own spacecraft hovering over the Moon’s surface.
The Moon and How to Observe It — PDF p. 83Lunar eclipses are better viewed through binoculars than through a telescope: both eyes can allow the subtle colors in the umbra to be readily discerned, and the totally eclipsed Moon hovering against a starry background often appears stunningly 3-dimensional.
The Moon and How to Observe It — PDF p. 111to crowd or gather closely together
Huddled together in the southwestern part of the area, the large craters Purbach, Regiomontanus, Aliacensis and Blancanus are a splendid sight when they have emerged from the morning terminator.
The Moon and How to Observe It — PDF p. 206Alternatively, it has been suggested that there might instead be large, diffuse clouds of material composed of billions of tiny particles ranging from a centimeter to less than a micron in diameter huddled in the vicinity of the Moon’s Lagrangian points.
The Moon and How to Observe It — PDF p. 67covered with small rounded mounds or irregular rises
The oldest is composed of highly eroded ancient craters and basins, interspersed with younger cratered areas, smooth plains, hummocky plains, ridges, escarpments and fractures.
The Moon and How to Observe It — PDF p. 69A broad, hummocky plain lies between Montes Cordillera and Montes Rook, a 620-km-diameter inner mountain ring of the Orientale basin.
The Moon and How to Observe It — PDF p. 196combining features or components of different types
This may be a rare example of a hybrid rille – one that originally formed as a result of crustal tension but that later experienced volcanic activity along its length.
The Moon and How to Observe It — PDF p. 42The most widely available eyepieces have a barrel diameter of 1.25 inches, and these can be mounted to a .965-inch eyepiece tube using an adapter or a hybrid star diagonal (a mirror that flips the image 90°).
The Moon and How to Observe It — PDF p. 247a proposed explanation that can be tested against evidence
Now disfavored, the fission hypothesis of the formation of the Moon was first proposed in the 19th century.
The Moon and How to Observe It — PDF p. 13imagined or proposed for the purpose of reasoning
Make an observation of the shadow cast by a hypothetical mountain peak located at 10°N, 10°W.
The Moon and How to Observe It — PDF p. 238formed by the cooling and solidification of molten rock
Some of these objects are blatant advertisements for the power of asteroidal impact, while others display bountiful evidence of having been extensively modeled from within by igneous or heat-related activity.
The Moon and How to Observe It — PDF p. 69All the Moon’s rocks have been formed in processes that involved high temperatures; this includes igneous rocks that formed at high pressures deep beneath the Moon’s crust, volcanic rocks that solidified at the Moon’s surface and various shock-metamorphosed rocks and breccias that were created during the high temperatures and pressures of impact.
The Moon and How to Observe It — PDF p. 25to light a surface or make it visible by light
Some of the Moon’s brighter albedo features are noticeable even when they are not directly illuminated by the Sun, but instead bathed in the glow of earthshine.
The Moon and How to Observe It — PDF p. 45When the area is illuminated by a low early morning or late afternoon Sun, a 150mm telescope should be just sufficient to resolve the tiny crater itself.
The Moon and How to Observe It — PDF p. 48the lighting of a surface, especially its angle and intensity
Other clearly visible examples of normal faults can be found in the maria, where they show up well under low angles of illumination.
The Moon and How to Observe It — PDF p. 41Some areas of the Moon do possess delicate, but noticeable, coloration, and the observed intensity of these colors varies with their illumination.
The Moon and How to Observe It — PDF p. 45images collectively, especially those obtained by cameras or remote sensing
Clementine imagery and Arecibo radar mapping revealed the last hidden 1 percent of the lunar globe, located in the vicinity of the south pole (formerly known as ‘Luna Incognita’); therefore, libration maps V and VI on pp. 186–187 have been revised in this edition.
Atlas of the Moon — PDF p. 112to place or become enclosed deeply within a surrounding medium or shadow
Of course, when a satellite is immersed in its primary’s own shadow and becomes eclipsed, the terminator disappears, since there is no direct sunlight falling onto the eclipsed body.
The Moon and How to Observe It — PDF p. 62Much depends on cloud and high-altitude dust in the Earth’s atmosphere and how deeply the Moon is immersed into the Earth’s umbral shadow.
The Moon and How to Observe It — PDF p. 126the entry of a celestial feature or body into a shadow
Through low-power binoculars, the following features can be used as shadow contact timing points (in order of immersion): Grimaldi, Aristarchus, Kepler, Copernicus, Tycho, Plato, Manilius, Posidonius, Proclus, and Langrenus.
The Moon and How to Observe It — PDF p. 127It is possible to time, to the nearest minute, the passage of the edge of the umbra over certain prominent lunar features; contact timings are made upon the feature’s immersion into, and emergence from, the umbra.
The Moon and How to Observe It — PDF p. 127a body that strikes the surface of a planet, moon, or other object
The core of the impactor joined the body of the Earth, while the mantles of both objects were mixed and splashed out into space.
The Moon and How to Observe It — PDF p. 17Since the Moon has no atmosphere to slow these objects as they plummet to the surface, the average impactor hits with an unimpeded interplanetary velocity of more than 70,000 km/hour.
The Moon and How to Observe It — PDF p. 29to give, transmit, or communicate a force or quality
Basin formation imparted tremendously powerful seismic waves into the lunar crust, which traveled around the Moon to converge on the other side, immediately opposite the impact site.
The Moon and How to Observe It — PDF p. 37The additional gravitational attraction of this displaced tidal bulge actually tugs on the Moon and imparts angular momentum to it.
The Moon and How to Observe It — PDF p. 54not easily noticed or clearly visible
Around Mons Rümker, the marial plains are crossed by one or two very inconspicuous wrinkle ridges and are dusted with a few rays, and it is one of the most topographically bland areas on the entire Moon.
The Moon and How to Observe It — PDF p. 178Our satellite seems to be a practically dead body, and its manifestations of residual internal geological activity are both rare and inconspicuous (p. 211).
Atlas of the Moon — PDF p. 9to include or combine as part of a whole
There are some intriguing variations on the fission theme, including theories that incorporate Mars into the material of the original spinning proto-planet.
The Moon and How to Observe It — PDF p. 14This requires the exact scale of the image to be known and usually involves incorporating the Moon’s apparent angular diameter at the time of the image into the equation.
The Moon and How to Observe It — PDF p. 238not clearly defined, fixed, or bounded
The northern boundary is formed by the Carpathian Mountains; the southern border is indefinite, linking with Mare Cognitum.
Atlas of the Moon — PDF p. 46a notch, recess, or inward depression
Bullialdus’ rim rises to more than 3,500 m above its floor, and it has a marked indentation along the southeast rim, possibly the result of having impacted so close to the crater Bullialdus A (25 km).
The Moon and How to Observe It — PDF p. 182Using a 150 mm telescope at high magnification, close examination will reveal a short (northeast–southwest) line of two hills on each side of the main peak, in addition to a tiny indentation on the main peak’s summit.
The Moon and How to Observe It — PDF p. 210marked by recesses, notches, or inward curves
The surfaces of lunar rocks studied under the microscope are indented with countless tiny impact pits, many of them surrounded by a splash pattern of melted material.
The Moon and How to Observe It — PDF p. 29Barrow itself intrudes upon the southwestern part of Meton (122 km), a flat-floored crater with a well-defined rim that is indented with a number of large bays.
The Moon and How to Observe It — PDF p. 141not sharply defined or easily seen
Ray material can be traced around Doppelmayer K (6 km) and a few small unnamed craters, along with several indistinct linear streaks in the western half of the mare.
The Moon and How to Observe It — PDF p. 198Alphonsus’s southern wall is disrupted by a large, indistinct (unnamed) crater and several linear valleys.
The Moon and How to Observe It — PDF p. 208relating to electromagnetic radiation with wavelengths longer than visible red light
CCDs are sensitive to infrared light, and the lens assembly may contain an infrared-blocking filter; without the filter, a really clean focus through a refractor is not possible, since infrared is focused differently from visible light.
The Moon and How to Observe It — PDF p. 102to prevent, restrain, or slow a process
Vitamin C helps protect the eyes against ultraviolet radiation and, being an antioxidant, it inhibits the natural oxidization of cells.
The Moon and How to Observe It — PDF p. 240The development of cataracts and age-related macular degeneration (AMD) is inhibited by Vitamin E, a substance found in wheat germ oil, sunflower seed and oil, hazelnuts, almonds, wheat germ, fortified cereals and peanut butter.
The Moon and How to Observe It — PDF p. 240too many to be counted
The Copernican Period now shows the effects of surface erosion by innumerable meteoroids and micrometeoroids – a relentless pummeling that has gradually rounded the lunar hills and produced a layer of fine soil.
The Moon and How to Observe It — PDF p. 21Over the eons, innumerable meteoroids, asteroids and cometary nuclei have collided with the Moon.
The Moon and How to Observe It — PDF p. 69existing or travelling between planets
Atmosphereless Mercury and the Moon have been fully exposed to the harsh vacuum of space and subjected to bombardment by interplanetary dust, meteoroids, asteroids and comets, in addition to x-rays, gamma rays and cosmic rays.
The Moon and How to Observe It — PDF p. 27Since the Moon has no atmosphere to slow these objects as they plummet to the surface, the average impactor hits with an unimpeded interplanetary velocity of more than 70,000 km/hour.
The Moon and How to Observe It — PDF p. 29the way two or more factors influence one another
It causes a periodic displacement in the Moon’s apparent longitude in the sky, amounting to as much as 39.5 ′ (a little more than the Moon’s apparent angular diameter), and results from the interplay of the gravitational attraction of the Earth and Sun.
The Moon and How to Observe It — PDF p. 55to cross or meet at a point or line
The two points at which these planes intersect are called the ascending and descending nodes.
The Moon and How to Observe It — PDF p. 53to occur or be situated between other things
A casual observer might think this indicates a straight-through optical configuration without any intervening prisms.
The Moon and How to Observe It — PDF p. 243having many complex and closely connected details
Intricate systems of interconnected linear rilles can be found in some maria and within many larger craters.
The Moon and How to Observe It — PDF p. 41Under a low angle of illumination, Mare Serenitatis displays an intricate system of wrinkle ridges that snake their way around the sea, keeping roughly parallel to its border.
The Moon and How to Observe It — PDF p. 133to arouse curiosity or interest
There are some intriguing variations on the fission theme, including theories that incorporate Mars into the material of the original spinning proto-planet.
The Moon and How to Observe It — PDF p. 14understanding gained without conscious step-by-step reasoning
Given all of these variables, knowledge, experience and intuition all count a great deal when it comes to taking good photographs of the Moon.
The Moon and How to Observe It — PDF p. 98a reversal of the normal order or arrangement
This produces an inversion of the ejecta blanket’s layering compared with the original layering of the impact site; material once forming the top layers at the impact site are overlain by material that originally lay beneath it.
The Moon and How to Observe It — PDF p. 32to turn upside down or reverse orientation
In recent years, a new style of small binoculars has appeared; it uses an inverted Porro prism design, leading to a U-shaped shell with objective lenses that may be closer together than the eye lenses.
The Moon and How to Observe It — PDF p. 243Straight-through finderscopes deliver an inverted view, so they are unsuitable for terrestrial use.
The Moon and How to Observe It — PDF p. 246an island, especially a small one
The largest ‘isle’ here is the crater Copernicus, which is surrounded by light ejecta, visible under high illumination.
Atlas of the Moon — PDF p. 46having a rough outline with sharp, irregular points
Wearing down solid rock, the continual rain of meteoroids has served to erode the Moon’s surface, smoothing mountain peaks that were once as sharp and jagged as their terrestrial counterparts.
The Moon and How to Observe It — PDF p. 29Meteoroid erosion has affected the lunar mountains so that their summits are gently rounded; there are no jagged Matterhorn-type peaks in any of the Moon’s mountain ranges, contrary to the illusion of spirelike peaks caused by the long shadows they cast when illuminated by a low morning or evening Sun.
The Moon and How to Observe It — PDF p. 43a soft, clear, gel-like substance
This lens focuses light across a chamber filled with vitreous humor, a clear jelly that gives the eyeball its rigidity, and an upside-down image is projected onto the retina inside the back part of the eyeball.
The Moon and How to Observe It — PDF p. 239a place where two or more features meet
Finally, it narrows to about 7 km wide at its junction with Mare Frigoris.
The Moon and How to Observe It — PDF p. 145Montes Riphaeus, a substantial mountain spine, rises at the junction between Mare Cognitum and Oceanus Procellarum.
The Moon and How to Observe It — PDF p. 179relating to motion or the energy of motion
Any meteoroid large enough to slice down into the lunar crust generates tremendous pressures and temperatures as its kinetic energy (the product of the meteoroid’s mass and the square of its velocity) is converted into shock waves and heat that is imparted into the surrounding crust.
The Moon and How to Observe It — PDF p. 30a sharp bend or irregular twist
A marked “kink” – the result of a landslide – can also be observed on Copernicus’s eastern rim.
The Moon and How to Observe It — PDF p. 121A small crater, Copernicus A (2.5 km) occupies a ledge in the middle of the terracing of the inner eastern wall (discernible in a 150 mm telescope), and there is a prominent kink in Copernicus’s eastern rim.
The Moon and How to Observe It — PDF p. 160a rounded control or projection
Focusing is achieved by looking directly at the magnified image of the Moon through the camera viewfinder and adjusting the telescope’s focusing knob until a sharp image is seen.
The Moon and How to Observe It — PDF p. 98Better altazimuth models are provided with slow-motion knobs that allow the telescope to be moved without having to push its tube around.
The Moon and How to Observe It — PDF p. 254covered with or shaped by many small rounded projections
The concentration of these seismic waves led to the formation of localized areas of chaotic terrain, where pre-existing structures were shaken to their foundations, producing a knobbly, textured landscape.
The Moon and How to Observe It — PDF p. 37Montes Haemus are one of the Moon’s less grand-looking named mountain ranges, a narrow, knobbly plateau some 400 km in length that marks the southwestern boundary of Mare Serenitatis.
The Moon and How to Observe It — PDF p. 135a small dark lunar plain designated as a lake in lunar nomenclature
Solis Lacus, the so-called “eye of Mars, ” is an interesting dark patch situated in a brighter circular region, outlined by a dusky crescent.
The Moon and How to Observe It — PDF p. 74Nearby, on the northern border of Lacus Somniorum (Lake of Dreams), can be found the prominent duo of Atlas (87km) and Hercules (67km).
The Moon and How to Observe It — PDF p. 121the Greek letter λ, used as a symbol for longitude or wavelength
Selenographic longitude, λ (lambda), is measured along the equator from the central meridian to the meridian containing a given point.
Atlas of the Moon — PDF p. 11a conspicuous feature used as a point of reference
But, as the major landmarks are noted, they can be used as stepping stones to hop across to other, more subtle, features that may have originally been overlooked.
The Moon and How to Observe It — PDF p. 83Anaxagoras is the “Tycho of the north” – the most prominent landmark in the north polar region, a deep crater with a sharp circular rim.
The Moon and How to Observe It — PDF p. 141a mass of rock or soil moving down a slope
A marked “kink” – the result of a landslide – can also be observed on Copernicus’s eastern rim.
The Moon and How to Observe It — PDF p. 121Copernicus has a generally circular outline with a sharp, rather scalloped rim – the consequence of multiple landslides along weak points in the impact-fractured crust.
The Moon and How to Observe It — PDF p. 160angular distance north or south of an equator
From southern temperate latitudes, the full Moon appears very low above the northern horizon during December.
The Moon and How to Observe It — PDF p. 53From the latitude of London, the Moon can never appear closer than around 23° to the zenith.
The Moon and How to Observe It — PDF p. 53molten rock that reaches and flows across a surface
KREEP was brought to the surface mixed within magmatic intrusions and spread in lava flows, and it has been redistributed around the Moon by impacts.
The Moon and How to Observe It — PDF p. 19Basaltic in composition, the marial lava flows had the viscosity of motor oil and were ductile and fast-moving.
The Moon and How to Observe It — PDF p. 20a narrow horizontal shelf or projecting ridge
To the west of the crater rim there is a clear boundary between the concentric ridges and the radial features, forming a broad ledge some 20 km wide.
The Moon and How to Observe It — PDF p. 160A small crater, Copernicus A (2.5 km) occupies a ledge in the middle of the terracing of the inner eastern wall (discernible in a 150 mm telescope), and there is a prominent kink in Copernicus’s eastern rim.
The Moon and How to Observe It — PDF p. 160valid, acceptable, or in accordance with proper rules
This is perfectly legitimate as long as the observer isn’t adding any detail that wasn’t actually observed.
The Moon and How to Observe It — PDF p. 87a handle used to move or adjust a mechanism
Zooming involves physically altering the distance between the lenses inside the eyepiece using an external lever.
The Moon and How to Observe It — PDF p. 242the apparent oscillation of the Moon that lets observers see slightly beyond its mean limb
Optical libration results from the ever-changing aspect (within strict limits) of the Moon’s presentation to the terrestrial observer, combined with the position from which the Moon is viewed.
The Moon and How to Observe It — PDF p. 55Physical libration is an actual wobble of the Moon about its own center of gravity, and it is a real, though exceedingly small, oscillation, rather than an apparent one.
The Moon and How to Observe It — PDF p. 55to remain somewhere longer than expected or necessary
It is possible to produce a wonderful tour of the Moon and its terminator, taking time to linger over features of interest and zoom in on them.
The Moon and How to Observe It — PDF p. 101Copernicus is so overwhelmingly spectacular that the observer is tempted to linger over it for hours on end, but it is worthwhile paying closer scrutiny to these least obvious attractions of the region.
The Moon and How to Observe It — PDF p. 162a rounded projection or distinct section of a feature
These features, which often have broad, ill-defined points of origin, have very low profile and their margins often extend into multiple well-defined lobes.
The Moon and How to Observe It — PDF p. 39A brilliant lobe of ejecta from southwestern Aristarchus crosses to the south of Herodotus, coating the southern part of its dark lava-flooded floor with a bright ray.
The Moon and How to Observe It — PDF p. 171very high or elevated
Its lofty summit would catch the sunlight some 14 hours before local sunrise.
The Moon and How to Observe It — PDF p. 74Mare Crisium has imposing lofty mountain borders in the west, whose clean-cut scarp faces shine brilliantly in the morning.
The Moon and How to Observe It — PDF p. 150angular distance east or west of a reference meridian
Libration in longitude is produced by the ellipticity of the Moon’s orbit, which leads to a variation in its angular velocity.
The Moon and How to Observe It — PDF p. 56Maximum libration in longitude occurs about a week after perigee and apogee – at perigee and apogee there is no libration in longitude.
The Moon and How to Observe It — PDF p. 56relating to longitude or extending lengthwise
The shape of this ellipse changes dramatically, especially at the extremes of longitudinal libration.
Atlas of the Moon — PDF p. 106to appear large, close, or threatening
Traced backwards in time, it can be deduced that several billion years ago the Moon orbited just a few tens of thousands of kilometers away from the Earth, and a terrestrial day matched a lunar “month” of just a few hours; the Moon would have loomed apparently motionless over one hemisphere of the Earth, a great, hot orb that produced solar and lunar eclipses every few hours.
The Moon and How to Observe It — PDF p. 14an area of land or terrain lower than its surroundings
Lacus Excellentiae, an irregularly shaped plain of lava centered around the small, flooded crater Clausius (25 km), occupies some 22,000 sq km of the lowlands some distance north of Schickard.
The Moon and How to Observe It — PDF p. 204one complete cycle of lunar phases, about 29.5 days
A feature observed under a midday Sun on one lunation may appear somewhat brighter (or dimmer) during the following lunation at midday.
The Moon and How to Observe It — PDF p. 45Every 29.5 days it goes through a complete cycle of phases, waxing from new Moon to full Moon and waning to new Moon once more, the synodic month, or lunation.
The Moon and How to Observe It — PDF p. 61molten or partly molten rock beneath a planetary surface
Denser (iron- and magnesium-rich) minerals crystallizing in the melt sunk into the depths of the magma.
The Moon and How to Observe It — PDF p. 18Denser (iron- and magnesium-rich) minerals sank deep in the magma, later to become the Moon’s mantle, from which the lavas of the lunar maria were later derived.
The Moon and How to Observe It — PDF p. 19relating to magma or processes involving magma
Minerals like anorthosite would have been less dense than the magma melt, and they floated to the surface, aided by upwelling magmatic convection currents, to accumulate in gigantic “rockbergs” at the Moon’s surface.
The Moon and How to Observe It — PDF p. 18KREEP was brought to the surface mixed within magmatic intrusions and spread in lava flows, and it has been redistributed around the Moon by impacts.
The Moon and How to Observe It — PDF p. 19the chemical element with atomic number 12
Typically around 50% of lunar basalt comprises the mineral pyroxene, a calcium–magnesium–iron silicate.
The Moon and How to Observe It — PDF p. 25Other plagioclase-rich rocks make up a group called the “Mg-suite, ” whose pyroxene and olivine minerals are rich in the metallic element magnesium (Mg).
The Moon and How to Observe It — PDF p. 26magnetic force or the physical phenomena associated with magnetic fields
Alternatively, it may have been caused by cometary impact, the area’s strong magnetism having been transplanted to the lunar surface from the comet’s nucleus.
The Moon and How to Observe It — PDF p. 176Studies of remnant magnetism frozen into ancient lunar rocks as they solidified show that the lunar magnetic field strength in the past was at least 3,000 nT and was likely to have been produced in the hot molten interior by a dynamo effect similar to that which produces the Earth’s magnetic field.
The Moon and How to Observe It — PDF p. 22the factor by which an optical instrument enlarges an apparent image
While the terminator in these areas can be traced at low power through the telescope eyepiece, high magnification will reveal a gradual fade from the day to night hemispheres.
The Moon and How to Observe It — PDF p. 62Each area breaks down into further tonal grades when scrutinized at higher magnification, and each area will tend to appear darker the nearer it lies to the terminator.
The Moon and How to Observe It — PDF p. 86to make an object appear larger through an optical instrument
If the digicam has a zoom, the lunar terminator can be magnified, aiding focusing further.
The Moon and How to Observe It — PDF p. 100A typical pair of zoom binoculars can be adjusted to magnify from, say, 15× to as much as 100×.
The Moon and How to Observe It — PDF p. 242size, extent, or a logarithmic measure of astronomical brightness
An average of 3,000 moonquakes takes place each year – annually there are 300 times as many quakes of similar magnitude on the Earth.
The Moon and How to Observe It — PDF p. 21Since there is no seismic activity on the Moon other than that produced by natural causes, seismometers operated on the Moon can measure disturbances several orders of magnitude fainter than those detected on the Earth.
The Moon and How to Observe It — PDF p. 21impressively grand or dignified
Mare Orientale, a majestic multiring impact basin that lies largely on the Moon’s far side, just past the southwestern limb, shows an impressive system of mountains.
The Moon and How to Observe It — PDF p. 43Plato (101 km) is a majestic crater, one of the most prominent landmarks in this sector of the Moon.
The Moon and How to Observe It — PDF p. 165to show or reveal something clearly
This manifests itself by an apparent “swinging” to the left of the lunar globe to reveal an area that normally lies beyond the right-hand edge of the Moon.
Atlas of the Moon — PDF p. 7an observable sign or expression of a process
Our satellite seems to be a practically dead body, and its manifestations of residual internal geological activity are both rare and inconspicuous (p. 211).
Atlas of the Moon — PDF p. 9The domes are manifestations of lunar volcanism and are observable only when close to the terminator.
Atlas of the Moon — PDF p. 104the thick rocky layer between a body's crust and core
In fact, the Moon has about the same density as the Earth’s mantle, but the Earth itself is 1.6 times denser than the Moon.
The Moon and How to Observe It — PDF p. 12It is thought that the Moon’s differentiated crust and mantle may have formed by about 4.4 billion years ago, only a couple of hundred million years after the Moon’s formation.
The Moon and How to Observe It — PDF p. 18a large, dark plain of basalt on the Moon
More than 30% of the near-side was covered with mare material, compared with less than 3% of the far side.
The Moon and How to Observe It — PDF p. 20There are more than a dozen notable mascons on the Moon’s near side, the largest of which lie in Mare Imbrium, Mare Serenitatis, Mare Crisium, Mare Nubium and Mare Fecunditatis.
The Moon and How to Observe It — PDF p. 23the plural of mare, referring to the Moon's dark basaltic plains
This material was later to become the Moon’s mantle, from which the relatively iron- and magnesium-rich lavas of the lunar maria were later derived.
The Moon and How to Observe It — PDF p. 18Denser (iron- and magnesium-rich) minerals sank deep in the magma, later to become the Moon’s mantle, from which the lavas of the lunar maria were later derived.
The Moon and How to Observe It — PDF p. 19relating to the lunar maria
A number of major impacts carved out the marial basins 2: 3.8 billion years ago, which were subsequently flooded by lava 3: 3.3 billion years ago.
The Moon and How to Observe It — PDF p. 20Basaltic in composition, the marial lava flows had the viscosity of motor oil and were ductile and fast-moving.
The Moon and How to Observe It — PDF p. 20a compact group or block of mountains
Those of the Moon’s ringed basins that range from 140 to 175 km in diameter have a sizable central massif, caused by crustal rebound and uplift, surrounded by an inner ring of scattered mountains.
The Moon and How to Observe It — PDF p. 36The crater Arandas in Acidalia Planitia looks remarkably like the lunar crater Alpetragius, with a similarly huge central massif.
The Moon and How to Observe It — PDF p. 74a material or framework in which other elements are embedded
This sample consists of fragments of glass, minerals and rock cemented together in a glassy matrix.
The Moon and How to Observe It — PDF p. 28Typical breccias contain coarse fragments embedded in a fine-grained crystal matrix.
The Moon and How to Observe It — PDF p. 26only average or not very good
In mediocre viewing conditions, it is best to multiply the pixel size by 2 to arrive at a more suitable focal ratio.
The Moon and How to Observe It — PDF p. 102An image produced by an astronomical CCD may have far less signal noise and a higher number of pixels than one taken with a webcam, but in mediocre viewing conditions, the chances that the image was taken at the precisely right moment are small.
The Moon and How to Observe It — PDF p. 103a lens with one concave and one convex surface, or a curved liquid surface
Light enters the tube through the meniscus, refracts onto the primary mirror and is reflected into the eyepiece via the secondary mirror and a central hole in the primary.
The Moon and How to Observe It — PDF p. 249MCTs use a spherical primary mirror and a deeply curved spherical lens (a meniscus) at the front of the tube.
The Moon and How to Observe It — PDF p. 249to combine or become indistinguishable as one
The resolution of a telescope can be determined by measuring the minimum angular distance between two points that can be barely separated; the limit is reached when the images of the two points merge into one.
Atlas of the Moon — PDF p. 107a line of constant longitude running through both poles
For example, the eastern part of the large crater Ptolemaeus lies on the Moon’s mean central meridian, at a selenographic longitude of 0°.
The Moon and How to Observe It — PDF p. 91Short A lies on the Moon’s central meridian, 13° (390 km) from the south pole.
The Moon and How to Observe It — PDF p. 221a streak of light produced when a small space object enters an atmosphere
Many of the brief flashes may actually have been caused by meteors in the Earth’s own atmosphere that have approached along the observer’s line of sight.
The Moon and How to Observe It — PDF p. 46a natural object from space that survives passage through an atmosphere and reaches a surface
A small number (just a few dozen) of meteorites found on Earth are known to be material that originated on the Moon, having been thrown from the lunar surface by the explosive power of impacts.
The Moon and How to Observe It — PDF p. 29Meteorites found on the Earth have been shown to originate from asteroids, with a few that are known to have been blasted from the Moon and Mars.
The Moon and How to Observe It — PDF p. 46a small natural solid body moving through space
Breccia is a composite rock made up of fragments created through the processes of impact shattering, mixing, melting and recrystallization of rock during the high energies released during meteoroid and asteroid impacts.
The Moon and How to Observe It — PDF p. 26A meteoroid about 10 m across would be sufficient to penetrate the typically deep regolith in the highlands.
The Moon and How to Observe It — PDF p. 30to mix or combine while remaining partly distinguishable
Thales is the center of one of the Moon’s brighter ray systems, and its rays mingle with those surrounding Anaxagoras, some 720 km to the west.
The Moon and How to Observe It — PDF p. 142The western heights of Montes Haemus mingle with the eastern part of Montes Apenninus, the Moon’s largest and most imposing mountain range, 600 km in length and forming a spectacular sweeping border to southeastern Mare Imbrium.
The Moon and How to Observe It — PDF p. 135very small, or a small-scale representation
In addition, the numbers of adjacent sections are printed alongside, and at the bottom there is a miniature map of the near side of the Moon with the position of the particular section marked upon it.
Atlas of the Moon — PDF p. 16extremely small
The other Jovian satellites are comparatively small, ranging from the irregular Amalthea (270 × 171 × 150 km) to the minuscule Leda, 15 km across.
The Moon and How to Observe It — PDF p. 76The minuscule crater measures just 30 microns in diameter.
The Moon and How to Observe It — PDF p. 33having an irregular or badly formed shape
In the northeast, pressing against Hipparchus’s inner wall, the crater Horrocks (30 km) has a sharp, though somewhat misshapen, rim and marked internal terracing.
The Moon and How to Observe It — PDF p. 209In the west, with the flooded, misshapen craters Fracastorius E (9 km), a group of three, small, flooded craters are joined, and to its south lies Fracastorius H (21 km), an overlapping, flooded crater trio.
The Moon and How to Observe It — PDF p. 227imitating or resembling something without being the real thing
Sometimes the lunar halo may be host to parselene (also known as “mock Moons” or “Moon dogs”), diffuse images of the Moon located 22° to either side of it, caused by the moonlight’s refraction by ice crystals in the upper atmosphere.
The Moon and How to Observe It — PDF p. 110a self-contained unit that forms part of a larger system or spacecraft
The Apollo spacecraft consisted of three main sections: a command module, a service module, and a lunar module.
Atlas of the Moon — PDF p. 99The crew of the spacecraft consisted of three astronauts, who spent most of their time aboard the command module.
Atlas of the Moon — PDF p. 99relating to molecules
How could a spectroscope that is pointed directly towards the surface of the lifeless Moon possibly detect water, molecular oxygen and chlorophyll, the latter indicating the presence of land plants?
The Moon and How to Observe It — PDF p. 60the smallest unit of a substance retaining its chemical properties
Simultaneously, another important phenomenon occurs: the Sun ray, r, passing through the Earth’s atmosphere, is selectively scattered by the air molecules, the so-called Rayleigh scattering.
Atlas of the Moon — PDF p. 110melted by heat and in a liquid or partly liquid state
Instability within the proto-planet’s rapidly rotating molten mass, produced mainly by the gravitational pull of the Sun, caused it to elongate.
The Moon and How to Observe It — PDF p. 13Beneath this layer, some constituents of the core, at a temperature of 1,000°C, are likely to exist in a molten state.
The Moon and How to Observe It — PDF p. 21the quantity of motion of a body, equal to its mass multiplied by its velocity
The Earth–Moon system has the largest amount of angular momentum (a product of the objects’ masses and velocities) in the Solar System; what mechanisms could possibly account for this?
The Moon and How to Observe It — PDF p. 12The additional gravitational attraction of this displaced tidal bulge actually tugs on the Moon and imparts angular momentum to it.
The Moon and How to Observe It — PDF p. 54lacking variety or change
Much of the planet is covered by an undulating landscape of low relief, a monotonous terrain accounting for around 90% of the surface.
The Moon and How to Observe It — PDF p. 71On the whole, the area of Lacus Excellentiae is monotonous, devoid of obvious faulting or features constructed on a grand scale.
The Moon and How to Observe It — PDF p. 204an isolated mountain or peak in planetary nomenclature
The largest of them is Olympus Mons, a giant mountain with a base 500 km across and a height of 24 km.
The Moon and How to Observe It — PDF p. 74East of Montes Teneriffe is the prominent Mons Pico, an isolated mountain 2,400 m high, named in honor of the highest mountain on Tenerife.
The Moon and How to Observe It — PDF p. 116the plural of mons, used for mountain ranges or groups in planetary nomenclature
Its outer ring, 930 km in diameter, is made up of the Montes Cordillera.
The Moon and How to Observe It — PDF p. 43North of these brooding sentinels, cratered, hilly terrain rises from the flat expanses of Oceanus Procellarum (Ocean of Storms) to the west and blends into Montes Jura, a magnificent arc of peaks.
The Moon and How to Observe It — PDF p. 115the form, structure, and characteristic shapes of a feature
Leaving aside the evidence of the lunar rocks themselves, there is a clear pattern of impact-crater morphology spanning all size ranges, from the tiniest micrometeorite impact pits to the vast asteroidal impact basins.
The Moon and How to Observe It — PDF p. 28The observed morphology of lunar craters perfectly matches computer studies of impacts, in addition to ballistic impact experiments performed in laboratories and field studies of terrestrial craters (both natural impact features and manmade explosion craters).
The Moon and How to Observe It — PDF p. 28marked with irregular spots or patches of different colors or tones
Their surroundings are mottled with a peculiar “herringbone texture” made up of a mass of V-shaped hummocks that point towards the crater.
The Moon and How to Observe It — PDF p. 32Some areas of the surface are mottled with light, wispy streaks, superficially resembling lunar rays, but their origin is probably internal, having resulted from the intrusion of ice along fissures in the crust.
The Moon and How to Observe It — PDF p. 78a very large number of things
Low-viscosity lava, squeezed through very narrow volcanic vents, can produce fire fountains that spray a multitude of tiny droplets – successive eruptions are capable of building up quite steep-sided volcanic cones.
The Moon and How to Observe It — PDF p. 38Tycho’s rays spread in a multitude of bright linear fingers of varying length, the longest of which can be traced up to 1,500 km from Tycho.
The Moon and How to Observe It — PDF p. 123to find or follow a route through an area
Regular visits to the region, along with attempts to identify certain key features, will enable the observer to navigate the area successfully.
The Moon and How to Observe It — PDF p. 220a person who plans or directs a route, especially at sea or through unexplored regions
The science and technology of the second half of the 20th century have brought the Moon so close to us that we now regard it much the same way that 15th-century navigators contemplated the exploration of distant continents.
Atlas of the Moon — PDF p. 6The southern elongation of Mare Fecunditatis, with bright rays from the craters Petavius B and Snellius A, includes the giant crater Petavius (which forms a magnificent but coincidental chain with Langrenus, Vendelinus, and Furnerius) and a group of craters named after famous navigators.
Atlas of the Moon — PDF p. 75describing the weaker tides occurring near first and last quarter
These are called neap tides, and they occur during the first- and last-quarter lunar phases.
The Moon and How to Observe It — PDF p. 54the hemisphere of the Moon that normally faces Earth, or relating to it
More than 30% of the near-side was covered with mare material, compared with less than 3% of the far side.
The Moon and How to Observe It — PDF p. 20The youngest lunar rocks – the basaltic lava that filled the near-side impact basins – date from around 3 billion years, which makes them about as old as the oldest rocks found on the Earth.
The Moon and How to Observe It — PDF p. 24a cloud of gas and dust in interstellar space
Fission The fission theory states that the material of the Moon and Earth was once incorporated in a single proto-planet that accreted from material within the solar nebula around 4.6 billion years ago.
The Moon and How to Observe It — PDF p. 13Lunar-formation theories must also account for the fact that the nonradioactive, stable isotopes of oxygen ( 16O, 17O, 18O) in lunar and terrestrial rocks have identical relative abundances, implying that the Earth and Moon formed at the same distance from the Sun in the same general vicinity within the solar nebula.
The Moon and How to Observe It — PDF p. 12so small or unimportant that it can be disregarded
Internal heating and surface-deforming activity is believed to have been negligible in Callisto’s history, and there was certainly no volcanic activity.
The Moon and How to Observe It — PDF p. 77relating to a reflecting telescope design that uses a flat diagonal secondary mirror
Newtonian reflectors require occasional optical collimation, cleaning and realuminising of their mirrors.
The Moon and How to Observe It — PDF p. 244Simplified cross sections showing the light path through the three major types of telescope used by amateur astronomers – a refractor, a Newtonian reflector and a Schmidt-Cassegrain.
The Moon and How to Observe It — PDF p. 244the chemical element with atomic number 7
Nothing of the satellite’s surface can be seen from afar because it is wrapped in a thick, yellow blanket of nitrogen and methane.
The Moon and How to Observe It — PDF p. 78a point where an orbit crosses a reference plane
The ascending node is the point on the ecliptic where the Moon moves to the north of the ecliptic; the descending node marks the point where the Moon moves to the south of the ecliptic.
The Moon and How to Observe It — PDF p. 53a formal system of names used in a field
Many older atlases may contain errors of nomenclature or outmoded and unofficial designations for features. “Pickering, ” for example, was a name once unofficially given to Messier A in Mare Fecunditatis.
The Moon and How to Observe It — PDF p. 88A history of lunar cartography and nomenclature, written by the world’s foremost authority on the subject.
The Moon and How to Observe It — PDF p. 270despite that; nevertheless
Some of the images are over-processed and too contrasty to be of much use in seeing fine tonal detail, but it is a useful book to consult nonetheless.
The Moon and How to Observe It — PDF p. 271important or interesting enough to deserve attention
Under a high illumination, Atlas, with its light floor and two dark spots, and Hercules, with its dark floor and single bright spot, make a noteworthy sight.
The Moon and How to Observe It — PDF p. 154A number of these rays stretch vast distances across Oceanus Procellarum; particularly noteworthy is a duo of rays that reach across to the Aristarchus Plateau, almost 900 km to the northeast.
The Moon and How to Observe It — PDF p. 176a person who is new to or inexperienced in an activity
With its hundreds of craters and mountains and vast gray plains, the lunar surface can appear utterly confusing to a novice, but it becomes increasingly familiar over time.
The Moon and How to Observe It — PDF p. 83However, choosing the right telescope can be a difficult task for a novice.
The Moon and How to Observe It — PDF p. 245the plural of nucleus; central bodies or compact cores
Over the eons, innumerable meteoroids, asteroids and cometary nuclei have collided with the Moon.
The Moon and How to Observe It — PDF p. 69The ice is thought to have been brought to the Moon by the impact of cometary nuclei, which are very large “dirty snowballs, ” clumps of water ice (in addition to other volatiles) mixed with rock and dust.
The Moon and How to Observe It — PDF p. 43to move or push slightly
For example, winter Full Moons are high, while summer Full Moons barely nudge above the southern horizon at midnight.
The Moon and How to Observe It — PDF p. 61unable to feel normally
Even if the clouds are threatening to obscure the Moon from view, or if your fingers are feeling numb with cold, it’s best to have an accurate half-completed drawing rather than an inaccurate drawing of the entire area you have observed.
The Moon and How to Observe It — PDF p. 84expressed in or relating to numbers
For numerical data on the Moon, see p. 19.
Atlas of the Moon — PDF p. 6slanting rather than parallel or perpendicular to a reference line or surface
Under oblique illumination a mountain range stands out, forming a nearly continuous wall around Mare Humboldtianum: this wall is partly intersected by a wall of the crater Belkovich, which lies in the libration zone.
Atlas of the Moon — PDF p. 23Under oblique illumination, numerous ridges are visible on the surface of the mare.
Atlas of the Moon — PDF p. 42to hide from view or make difficult to perceive; not clearly visible
Everyone has floaters, and they can be annoying because they can obscure small lunar features.
The Moon and How to Observe It — PDF p. 240The ancient basaltic lava flows of the cryptomaria were widely spread across large patches of the Moon’s surface but were completely obscured by piles of debris, many tens of meters thick, thrown out by subsequent major impact events.
The Moon and How to Observe It — PDF p. 38the degree to which something can be detected or observed
Because their magnitude is so tiny, physical librations do not have any appreciable impact upon the observability of lunar features.
The Moon and How to Observe It — PDF p. 59As with all near-limb regions, the observability of features around the Moon’s north polar region is subject to the effects of libration.
The Moon and How to Observe It — PDF p. 141a site or building equipped for astronomical observation
These days, few professional observatories ever turn their big telescopes towards the Moon other than to impress new students or to test out new equipment.
The Moon and How to Observe It — PDF p. 82Seeing Seeing varies from 0.5-arcsecond resolution on an excellent night at a world-class observatory site to 10 arcseconds on the worst nights.
The Moon and How to Observe It — PDF p. 250to occupy someone’s thoughts excessively
Often the new owner of a telescope seems obsessed with its magnifying power, as if this alone determines the excellence of the optical system.
Atlas of the Moon — PDF p. 107no longer used because it has been replaced or superseded
These and other classic terms, found in older literature (and, for the sake of continuity, also in previous editions of this book), are now considered obsolete and are seldom used anymore.
Atlas of the Moon — PDF p. 9the hiding of a distant celestial object by a nearer one passing in front
Lunar Occultations When a distant celestial object, be it a star, planet or deep sky object, is temporarily hidden from view by the Moon, a lunar occultation takes place.
The Moon and How to Observe It — PDF p. 66Occultation studies that accurately measure the drop in light at occultation have revealed Aldebaran to have a diameter of 20 milliseconds of arc – the apparent diameter of a star 50 km away.
The Moon and How to Observe It — PDF p. 66a very large dark lunar plain designated as an ocean
Others, like those around Kepler in Oceanus Procellarum, form a neat splash pattern that is equally bright all over.
The Moon and How to Observe It — PDF p. 32The Marius hills in Oceanus Procellarum create one of the Moon’s most spectacular volcanic landscapes: no fewer than a hundred volcanic cones and domes occupying an area of around 40,000 sq km.
The Moon and How to Observe It — PDF p. 39to counterbalance, or displaced from a central or expected position
This gives the impression that Aristarchus has an offset floor with differently sloped inner walls.
The Moon and How to Observe It — PDF p. 170But the Moon’s mass is only 2% that of the Earth’s, which offsets the barycenter considerably in the Earth’s direction, so much so that the common center of gravity is actually located within the Earth’s mantle, around 4,700 km from the center of the Earth.
The Moon and How to Observe It — PDF p. 52a greenish magnesium-iron silicate mineral common in igneous rocks
Other plagioclase-rich rocks make up a group called the “Mg-suite, ” whose pyroxene and olivine minerals are rich in the metallic element magnesium (Mg).
The Moon and How to Observe It — PDF p. 26The most abundant Mg-suite rocks are norite (plagioclase– pyroxene rock) and troctolite (plagioclase–olivine rock).
The Moon and How to Observe It — PDF p. 26an optical component or, in the plural, the optical system of an instrument
Refractors, with their fixed optics and enclosed system, are the least demanding of maintenance.
The Moon and How to Observe It — PDF p. 244Any major flaws in the optics, or dents and defects on the exterior of the instrument, are quickly revealed under the bright lights of the store.
The Moon and How to Observe It — PDF p. 245relating to light, vision, or instruments that use light
Optical libration results from the ever-changing aspect (within strict limits) of the Moon’s presentation to the terrestrial observer, combined with the position from which the Moon is viewed.
The Moon and How to Observe It — PDF p. 55Optical librations and the Moon’s phase determine the practical visibility of the Moon’s limb features.
The Moon and How to Observe It — PDF p. 58most favorable or effective under particular conditions
Using the webcam’s highest resolution (in most cases, an image size of 640 × 480), a frame rate of between 5 and 10 fps and a video clip of 5–10 seconds is optimum.
The Moon and How to Observe It — PDF p. 103As the dark-adapted eye has an average size of 7 mm, the optimum size of exit pupil for deep, dark-sky astronomical use measures 7 mm.
The Moon and How to Observe It — PDF p. 243relating to a projection that represents a spherical body as viewed from a great distance
The orthographic projection is commonly used for lunar charts and represents the Moon as it is observed on the celestial sphere at zero librations.
Atlas of the Moon — PDF p. 11We can do no better than to commence with the meridians 90°E and 90°W, which constitute the edge of the lunar disk as it is drawn in an orthographic projection of the near side.
Atlas of the Moon — PDF p. 93shockingly excessive or unreasonable
Unfortunately, newspaper advertisements announcing massive stock clearances of telescopes and binoculars are often full of outrageous hyperbole, with claims of extravagant magnifications and the ability of the instrument to show all the wonders of the Universe.
The Moon and How to Observe It — PDF p. 245to extend over and partly cover the same area as something else
Buried within this structure on the crater’s eastern wall is Mitchell (30 km), a crater that predates Aristoteles and a good example of a smaller crater that is overlapped by a larger crater.
The Moon and How to Observe It — PDF p. 143South of Darwin, overlapped by its southern wall, is the highly eroded crater Lamarck (115 km).
The Moon and How to Observe It — PDF p. 198to lie on top of or cover
Maria (almost entirely on the near side) have average depths of several kilometers and overlie a crust several tens of kilometers thick.
The Moon and How to Observe It — PDF p. 23All of the loose material that overlies the solid rocky crust of the Moon is named the “regolith, ” and it includes the largest boulders to the finest granules of soil.
The Moon and How to Observe It — PDF p. 24to cancel or take manual control over an automatic setting
It is necessary to override most of the software’s automatic controls: contrast, gain and exposure controls require adjusting to deliver an acceptable image.
The Moon and How to Observe It — PDF p. 103open and clearly observable rather than hidden
Examples of the variation in the morphology of impact features of different sizes can best be seen on the far side, where there has been little overt volcanic activity and lava flooding to alter their appearance (see Table 1.2).
The Moon and How to Observe It — PDF p. 37done with great care and thorough effort
Alternatively, the purpose may be to conduct painstaking research into, say, the changing appearance of low wrinkle ridges in Mare Humorum at the eyepiece of a very large telescope.
The Moon and How to Observe It — PDF p. 82An uncorroborated TLP report submitted by an inexperienced lunar observer using a small telescope is not likely to be afforded the same weighting as an observation of the same phenomenon made by an experienced lunar observer who has logged many hours at the eyepiece in a painstaking TLP search.
The Moon and How to Observe It — PDF p. 232a small lunar plain designated as a marsh in lunar nomenclature
None of Proclus’ rays cover the light gray patch of Palus Somni (Marsh of Sleep) west of Proclus.
The Moon and How to Observe It — PDF p. 122A prominent dark patch in southeastern Mare Imbrium is the lava plain Palus Putredinis (see Area One).
The Moon and How to Observe It — PDF p. 147a distinguished group of famous or honored people
As a result of the joint endeavors of many generations of selenographers, a unique pantheon has come into existence on the Moon, for it is here that names of deceased personalities can be added to commemorate their many and varied contributions to the development of science.
Atlas of the Moon — PDF p. 12an apparent shift in position caused by a change in the observer's viewpoint
Diurnal libration can appear something like the parallax effect produced by an alternate left- and right-eye views of a tennis ball placed 10 m away.
The Moon and How to Observe It — PDF p. 57Viewing the Moon with two eyes is a more pleasurable experience than using just one: even though the true 3-dimensional nature of the Moon is not possible to discern because the parallax effect is far too small, two eyes get the impression of a globe floating in space.
The Moon and How to Observe It — PDF p. 111a measurable factor or limit that helps define a system
Up to now we have considered only the optical parameters, but no matter how good these are, all will be lost if the telescope is inadequately mounted.
Atlas of the Moon — PDF p. 107a mixture of contrasting areas or parts
Different phases of lava flooding are quite evident telescopically, as many maria take on a patchwork appearance that suggests numerous phases of volcanic activity that erupted batches of lavas of slightly different chemical composition.
The Moon and How to Observe It — PDF p. 38uneven or marked by irregular areas of different appearance
West of Gambart, up to Reinhold (48 km), a scrambled mass of hills rises from the patchy mare.
The Moon and How to Observe It — PDF p. 161Under a high angle of illumination, the area looks rather patchy and blends into the surrounding mare.
The Moon and How to Observe It — PDF p. 176a quick or brief look
They are useful for quick peeks at the Moon in order to plan telescopic observing sessions.
The Moon and How to Observe It — PDF p. 111Lunar observers will find them useful to keep handy, since they can be used for quick peeks at the Moon and to discern which features might be on view along the lunar terminator, enabling detailed telescopic observing sessions to be planned in advance.
The Moon and How to Observe It — PDF p. 241land almost surrounded by water and joined to a larger land area
Around 65 million years ago, dinosaurs of the late Cretaceous period may have witnessed a significant asteroidal impact that devastated the (now) Yucatan peninsula area.
The Moon and How to Observe It — PDF p. 73the partially shaded outer region of a shadow
Since the Sun is an extended light source, some half a degree in diameter as seen from the Moon, the shadow is made up of two components – the umbra and the penumbra.
The Moon and How to Observe It — PDF p. 63The intensity of the darkness of the penumbra gradually rises from near zero at the penumbra’s outer edge to almost total shadow near the outer edge of the umbra.
The Moon and How to Observe It — PDF p. 63relating to or occurring within a penumbra
If the Moon traverses the outer penumbral shadow of the Earth, avoiding the umbra, a penumbral eclipse occurs.
The Moon and How to Observe It — PDF p. 65The penumbral shadow has no perceptible color, appearing gray with an outer edge that is impossible to detect visually.
The Moon and How to Observe It — PDF p. 65able to be noticed or detected
The penumbral shadow has no perceptible color, appearing gray with an outer edge that is impossible to detect visually.
The Moon and How to Observe It — PDF p. 65Because the penumbra has no perceptible color, appearing washed-out with an ill-defined outer edge that is impossible to detect visually, penumbral eclipses alone are pretty unspectacular.
The Moon and How to Observe It — PDF p. 126to rest in an elevated position, or such a position
The boulders must have been jarred from their original perches by a large moonquake – a vigorous shaking of the lunar crust that perhaps resulted from a large meteoritic impact close to Vitello.
The Moon and How to Observe It — PDF p. 48Another sharp-rimmed bowl crater, Bancroft (13.1 km) perches in the mountains immediately west of Archimedes (see Area Two), and to its west a 100mm telescope will show a small linear rille system.
The Moon and How to Observe It — PDF p. 157the point in an Earth-orbiting body's path that is nearest Earth
Having an apparent diameter about 12% larger at perigee, the apparent area of the perigee Moon is a huge 29% larger than at apogee.
The Moon and How to Observe It — PDF p. 53The imaginary line that joins the points of apogee and perigee – effectively the major axis of the Moon’s elliptical orbit – is called the “line of apsides”.
The Moon and How to Observe It — PDF p. 53situated near the outer edge of an area or field
Librations in latitude and longitude occur simultaneously and continuously, and their combined effects bring into view peripheral areas called libration zones.
Atlas of the Moon — PDF p. 7In practice, however, the peripheral areas are extremely difficult to observe with Earth-based telescopes, so the theoretical 59 percent has to be reduced to approximately 50 percent in practice.
Atlas of the Moon — PDF p. 93the outer edge or surrounding boundary of an area
For example, it has been suggested that the Gulf of Mexico marks the northern periphery of a major ancient crater, as large as the lunar South Pole–Aitken basin.
The Moon and How to Observe It — PDF p. 73Dorsum Oppel , the most prominent of these wrinkles, links with the flooded crater Ye r k e s(36 km) in the west and curves around the northwestern periphery of the mare for 300 km, where it is intercepted by half a dozen narrow wrinkles that cross the mare from the northwestern border.
The Moon and How to Observe It — PDF p. 150meeting a line or plane at a right angle
Matters would be simpler if the Moon’s axis of rotation were perpendicular to its orbital plane around the Earth.
The Moon and How to Observe It — PDF p. 57Over 2 years later, the ellipse’s major axis has rotated so that it is perpendicular to the Sun’s direction; apogee or perigee then coincides with either the first or last quarter, and by this time the orbital ellipse will have been gradually pulled back into a less eccentric shape.
The Moon and How to Observe It — PDF p. 55continuing without interruption or apparent end
Some deep craters in the vicinity of the lunar poles never receive direct sunlight; these permanently shadow-filled craters may be considered “polar pits of perpetual darkness.”
The Moon and How to Observe It — PDF p. 43a deviation in an orbit caused by gravitational influence
Variation is the second most important periodic perturbation of the Moon’s orbit.
The Moon and How to Observe It — PDF p. 55In addition to the slow advance of the line of apsides, the other major secular perturbation is seen in the recession of the line of nodes (the line joining the ascending and descending nodes, as described above), which moves westwards along the ecliptic by 1.6° each month.
The Moon and How to Observe It — PDF p. 55observable events or occurrences; the plural of phenomenon
These changes are known as TLP (transient lunar phenomena) and reportedly take the form of localised flashes, glows, obscurations, darkenings and changes of color that take place on a temporary and rather unpredictable basis.
The Moon and How to Observe It — PDF p. 232the chemical element with atomic number 15
KREEP is made up of Potassium (chemical symbol K), rare earth elements (REE) and phosphorus (P), and its unique chemical makeup allows it to be used as a marker for tracing the convoluted history of the Moon’s surface.
The Moon and How to Observe It — PDF p. 20a group of feldspar minerals rich in sodium or calcium
The most abundant Mg-suite rocks are norite (plagioclase– pyroxene rock) and troctolite (plagioclase–olivine rock).
The Moon and How to Observe It — PDF p. 26Anorthosites are made up of 90% or more of the mineral plagioclase, a very light-colored form of the mineral feldspar, and crystallized out of the Moon’s early magma “ocean” around 4.5 billion years ago to form the first lunar crust.
The Moon and How to Observe It — PDF p. 26a theater or institution for presenting and studying the night sky
The SPA hosts quarterly London meetings and free shows at the Tussaud’s London Planetarium.
The Moon and How to Observe It — PDF p. 267an extensive area of elevated, relatively level ground
Vallis Schröteri (Schröter’s Valley), the largest lunar sinuous rille, lies on the Aristarchus plateau in Oceanus Procellarum.
The Moon and How to Observe It — PDF p. 40However, there are no obvious lunar counterparts to features such as the Earth’s midoceanic ridges, Venus’s sprawling mountain plateaus and the circumpolar terraces of Mars.
The Moon and How to Observe It — PDF p. 69seemingly reasonable or likely to be true
In addition, any plausible theory must not overlook the fact that the Moon’s core is proportionately far smaller than the Earth’s – less than 3% its mass compared with 30% for the Earth’s core.
The Moon and How to Observe It — PDF p. 12an open area, here used for a broad widening in a valley
After 10 km the valley opens out into a diamond-shaped “plaza”, and it is at the entrance to this plaza that the narrow medial rille begins its journey.
The Moon and How to Observe It — PDF p. 145The plaza narrows to about 5 km, but afterwards the valley gradually widens to its maximum width about halfway along its length.
The Moon and How to Observe It — PDF p. 145a rising or outward-streaming cloud of material
The edge of the crater is deformed and uplifted as a plume of excavated material, made up of vaporized rock and larger rock fragments, is blasted outwards from the impact site.
The Moon and How to Observe It — PDF p. 30A plume of ejecta is thrown up from the Moon’s surface as the edge of the explosion cavity is deformed and uplifted.
The Moon and How to Observe It — PDF p. 31to project or extend outward
Some prominent mountains poke out of Mare Imbrium near its northern shoreline.
The Moon and How to Observe It — PDF p. 163East of Doppelmayer, Puiseux (25 km) is almost completely submerged beneath the mare, its remaining rim marked by a narrow ring of hills surrounding a smooth plain from which pokes a tiny central hill.
The Moon and How to Observe It — PDF p. 201having an outline made of several straight sides
They often have sharp rims and their floors are covered with mounds of debris that has slipped off the steep inner walls, giving the crater rim a distinctly scalloped or polygonal outline.
The Moon and How to Observe It — PDF p. 32The prominent crater Manilius (39 km), with its sharp polygonal outline, terraced inner wall and central peaks, lies on Mare Vaporum’s northeastern shore.
The Moon and How to Observe It — PDF p. 137a small round window in a ship or spacecraft
Many lunar observers will freely admit (I certainly do) that they often imagine their telescope eyepiece to be the porthole of their very own spacecraft hovering over the Moon’s surface.
The Moon and How to Observe It — PDF p. 83But afocal images are particularly prone to vignetting, where the Moon is surrounded by a dark circular border, making it look as though the photograph had been taken through the porthole of a spacecraft.
The Moon and How to Observe It — PDF p. 94to represent or depict visually
In the first case, a crater may be represented by a single circular outline, while in the second it could be portrayed to resemble its photographic image.
Atlas of the Moon — PDF p. 11For example, it is impossible to portray accurately, in a short time, a crater such as Copernicus, which is full of minute and complicated detail.
Atlas of the Moon — PDF p. 108the way something is represented or depicted
Relating the Moon’s face as seen through the telescope with its portrayal on lunar maps can often be challenging for the observer.
Atlas of the Moon — PDF p. 108Keeping in mind that the main function of this book is to serve as a guide for Earth-based observation, I will concentrate mostly on the general appearance of the lunar surface and its portrayal.
Atlas of the Moon — PDF p. 9the chemical element with atomic number 19
KREEP is made up of Potassium (chemical symbol K), rare earth elements (REE) and phosphorus (P), and its unique chemical makeup allows it to be used as a marker for tracing the convoluted history of the Moon’s surface.
The Moon and How to Observe It — PDF p. 20to come or move before something else
The eastern maria of Tranquillitatis, Crisium and Fecunditatis were extruded around 3.5 billion years ago, preceding the in-filling of Imbrium and Procellarum in the western hemisphere by several hundred million years.
The Moon and How to Observe It — PDF p. 21These special sites are known as Lagrangian points, and they exist at 60° preceding and following the Moon, as measured from the Earth.
The Moon and How to Observe It — PDF p. 67mainly or for the most part
Outside Tycho’s rim, a predominantly concentric set of ridges can be traced to a distance of around 35 km, but some radial structure can be discerned, including several crater chains to its northwest.
The Moon and How to Observe It — PDF p. 189of especially high quality and usually higher price
A number of reputable companies, including Tele-Vue, sell premium zoom eyepieces.
The Moon and How to Observe It — PDF p. 253A popular premium 8–24mm-focal-length zoom eyepiece has a narrow 40° apparent field when set at its longest focal length of 24mm, but as the focal length is reduced, the apparent field enlarges, up to 60° at 8mm.
The Moon and How to Observe It — PDF p. 253set or adjusted in advance
The most basic compact film and digital cameras have fixed lenses that are preset to focus on objects from a few metres away to infinity; this focus cannot be varied.
The Moon and How to Observe It — PDF p. 93to occupy a prominent or commanding position
Taruntius (56 km) presides over a fairly bland region full of gnarled hills and unimpressive, highly eroded craters like da Vinci (38 km), Lawrence (24 km) and Secchi (25 km).
The Moon and How to Observe It — PDF p. 152existing at or near the earliest stage of development
According to the theory of co-accretion, around 4.6 billion years ago, the Moon condensed from a primordial cloud of gas, dust and assorted debris in orbit around the Earth.
The Moon and How to Observe It — PDF p. 14a transparent optical element that refracts or redirects light
Because of the way that Roof prism binoculars fold the light, they offer generally less contrasty views than Porro prism binoculars.
The Moon and How to Observe It — PDF p. 243German-style Porro prism binoculars feature objective housings that screw into the main body containing the prisms; their modular nature makes them more susceptible to going out of collimation after knocks.
The Moon and How to Observe It — PDF p. 243an uncrewed spacecraft or instrument sent to investigate a target
High-resolution photographs taken by orbiting probes have uncovered many more examples of small, localized physical changes due to migrating surface debris.
The Moon and How to Observe It — PDF p. 48Fortunately, radar (from the Earth and from probes orbiting Venus) has provided an excellent means of discerning surface detail.
The Moon and How to Observe It — PDF p. 71the outline or side view of an object or surface feature
Compton is one of the furthest placed, clearly recognizable, far side features, and its western rim, seen in profile, is worth looking out for at times of very favorable libration.
The Moon and How to Observe It — PDF p. 155At an extreme libration west, Eichstadt and the Cordilleras in its vicinity remain visible in profile along the limb, while the rest of the basin lies beyond the limb.
The Moon and How to Observe It — PDF p. 196a cape or headland in planetary nomenclature
The rilles lead across to where Mare Serenitatis’ mountain border resumes, in the form of Montes Haemus, beginning with the crenulated headland of Promontorium Archerusa.
The Moon and How to Observe It — PDF p. 135Several more rilles lie near Promontorium Fresnel at the northern tip of the Montes Apenninus.
The Moon and How to Observe It — PDF p. 136a high point of land or terrain projecting into a sea or plain
The eastern promontory of Lacus Somniorum has a wide rille, Rima G. Bond.
Atlas of the Moon — PDF p. 31likely or susceptible to experience a particular problem
Features that lie within the Moon’s libration zones around the edge of the lunar disc on either side of longitudes 90°E and 90°W are prone to the effects of libration.
The Moon and How to Observe It — PDF p. 57But afocal images are particularly prone to vignetting, where the Moon is surrounded by a dark circular border, making it look as though the photograph had been taken through the porthole of a spacecraft.
The Moon and How to Observe It — PDF p. 94to support or hold something in position
To discern fine lunar detail it is important to hold binoculars as steady as possible, either propped up firmly against a solid object (like a car roof) or, better still, fixed to a tripod or a dedicated binocular mount.
The Moon and How to Observe It — PDF p. 241to travel or spread outward through a medium
The crust is compressed and shockwaves propagate outwards, fracturing the crust.
The Moon and How to Observe It — PDF p. 31to drive or push something forward
An exceptionally close encounter between Mercury and the Moon may have been sufficient to have both perturbed Mercury into its current eccentric orbit and propelled the Moon across the gulf of space into the Earth’s gravitational embrace.
The Moon and How to Observe It — PDF p. 16the action or means of driving a vehicle or object forward
But in August 1991 a team of astronomers at the California Institute of Technology made an excellent series of radar images of Mercury’s surface, using a high-power beam sent by the Jet Propulsion Laboratory’s Goldstone antenna in California.
The Moon and How to Observe It — PDF p. 71a person who searches an area for valuable minerals or other resources
On the other side of the Earth, at Wolf Creek in Western Australia, lies another beautifully proportioned impact crater, discovered by oil prospectors in 1947.
The Moon and How to Observe It — PDF p. 73to project outward or beyond a surrounding surface
The crater, 24 km in diameter, has a sharp rim, slumped internal walls and traces of impact-melt floor from which protrudes a small central peak.
The Moon and How to Observe It — PDF p. 33In some cases – notably in Mare Imbrium – the highest points of the original inner ring structure actually protrude through the wrinkle ridges to stand proudly above the surface as isolated peaks.
The Moon and How to Observe It — PDF p. 39nearness in position or distance
The practical visibility of any satellite of the Moon depends upon the object’s size, its reflective properties (albedo) and its proximity to the Moon’s glare.
The Moon and How to Observe It — PDF p. 68Because these craters lie in close proximity, the impacting body must have disintegrated at a low altitude and ploughed into the landscape from a southwesterly direction.
The Moon and How to Observe It — PDF p. 73a small device that blows air for removing dust
Dust particles should be carefully removed with a soft optical brush or an air puffer, and any residual dirt can be gently removed with optical lens wipes, each used once and applied in a single stroke.
The Moon and How to Observe It — PDF p. 248a monumental structure with a square or polygonal base and sloping sides meeting at a point
I would be ecstatically happy if my telescope allowed me to glimpse lunar features as big as the pyramids at Giza: even this degree of resolution is at the very limits of what can be achieved from the Earth, even through the largest professional telescopes.
The Moon and How to Observe It — PDF p. 249composed of rock fragments expelled by volcanic activity
Intermittent eruptions of volcanic ash and pyroclastic deposits produced steeper-sided volcanic cones.
The Moon and How to Observe It — PDF p. 38Unlike the dark halo craters that reveal the Moon’s cryptomaria, these features are undoubtedly volcanic vents that developed along deep-seated rilles and pumped out clouds of volcanic debris – glass beads formed in fountains of low-viscosity lava, layers of ash and pyroclastic deposits.
The Moon and How to Observe It — PDF p. 42a group of dark rock-forming silicate minerals containing calcium, magnesium, or iron
Typically around 50% of lunar basalt comprises the mineral pyroxene, a calcium–magnesium–iron silicate.
The Moon and How to Observe It — PDF p. 25Other plagioclase-rich rocks make up a group called the “Mg-suite, ” whose pyroxene and olivine minerals are rich in the metallic element magnesium (Mg).
The Moon and How to Observe It — PDF p. 26one of four equal sectors of a circle or region
Dark, circular sea in the southwestern quadrant of the Moon, its northeastern mountain border broken by the southern reaches of Oceanus Procellarum.
The Moon and How to Observe It — PDF p. 115A vast crater in the southwestern quadrant with a flooded, distinctly patchy floor dotted with several smaller craters.
The Moon and How to Observe It — PDF p. 122extending outward from a central point like a radius
Beyond the rim there is a considerable amount of physical structure, including prominent radial ridges and grooves, in addition to secondary cratering caused by the impact of substantial chunks of excavated bedrock.
The Moon and How to Observe It — PDF p. 32Such are the dynamics of impact that these radial structures do not follow perfectly straight lines – secondary-chain craters can follow quite curved, even sinuous, paths over the surface.
The Moon and How to Observe It — PDF p. 32to spread outward from a central point
A substantial system of secondary-impact craters,many of which are arranged in radial chains, radiates around the Orientale basin.
The Moon and How to Observe It — PDF p. 34A number of fine, low ridges can be seen among the rays radiating south of Aristarchus – piles of ejecta thrown out by the impact.
The Moon and How to Observe It — PDF p. 174energy transmitted as electromagnetic waves or particles
Alternatively, protons and ultraviolet radiation in the solar wind are capable of exciting the atoms in the vented gases, ionizing them to produce a glow discharge.
The Moon and How to Observe It — PDF p. 47Light (and other forms of electromagnetic radiation) takes an average of 1.3 seconds to cross the gulf of space between the Moon and the Earth.
The Moon and How to Observe It — PDF p. 52emitting radiation through spontaneous nuclear decay
The marial lava is thought to have formed in a hot radioactive decay melt layer, in places 100 km thick and up to 200 km beneath the lunar surface.
The Moon and How to Observe It — PDF p. 21After rapidly becoming a hot, internally molten globe because of the rapid accumulation of material and radioactive decay, the heavier metallic elements sank down through the outer layers of the protoplanet’s mantle to form an iron-rich core.
The Moon and How to Observe It — PDF p. 13a straight line from the center of a circle or sphere to its edge, or its length
Lunar rainbows are created under the same circumstances as rainbows produced by the Sun: a colored arc of 42° radius situated directly opposite the light source.
The Moon and How to Observe It — PDF p. 63Lunar rainbows form under the same circumstances as those of the Sun; both are colored arcs of 42° radius situated diametrically opposite the light source.
The Moon and How to Observe It — PDF p. 109occurring without a regular pattern or predictable position
Lunar seismic disturbances also occur as a result of random meteoroidal impacts.
The Moon and How to Observe It — PDF p. 21Some of the short-lived flashes that have been observed in random areas around the Moon may have been caused by meteoroid impacts on the lunar surface.
The Moon and How to Observe It — PDF p. 46to move gradually farther away or backward
Tidal forces have the net effect of slowing the Earth’s rotation by a tiny fraction of a second every century, and, in the same period, the Moon recedes from the Earth by several meters.
The Moon and How to Observe It — PDF p. 14The Moon is receding from the Earth by about 3.8 cm per year (38km every million years), a figure verified by precisely measuring the time taken for laser beams to reflect from instruments placed on the Moon’s surface.
The Moon and How to Observe It — PDF p. 54having the shape of a rectangle
A narrow valley separates it from Mons Gruithuisen Delta to the east; this is a rectangular mountain mass with rounded slopes and a base measuring some 25 km.
The Moon and How to Observe It — PDF p. 168Mare Nubium is a roughly rectangular sea with an east–west diameter of around 600 km and a total surface area of 254,000 sq km.
The Moon and How to Observe It — PDF p. 181to correct or put something right
A fresh drawing prepared indoors will, it is hoped, be far more accurate than the original telescopic sketch that it is based upon, as the observer will be able to recall little things about the original sketch that perhaps weren’t quite right and needed to be rectified on the neat drawing.
The Moon and How to Observe It — PDF p. 87to occur again, often periodically
This periodic gravitational tugging is a phenomenon known as evection, and causes the eccentricity of the Moon’s orbit to vary between 0.0432 and 0.0666, a complete cycle recurring every 87.1 years.
The Moon and How to Observe It — PDF p. 55a cylindrical object around which material can be wound
At the other end of the staff fasten a small squint hole; a used cotton reel or piece of card with a small hole punched out will do.
The Moon and How to Observe It — PDF p. 108the proportion or degree of incident radiation that a surface reflects
Earth’s reflectivity has been measured at around 20% brighter between October and July.
The Moon and How to Observe It — PDF p. 60The observed intensity of earthshine depends on the phases of the Moon and the Earth and the reflectivity of the Earth.
The Moon and How to Observe It — PDF p. 60a telescope that forms an image with a primary mirror
Simplified cross sections showing the light path through the three major types of telescope used by amateur astronomers – a refractor, a Newtonian reflector and a Schmidt-Cassegrain.
The Moon and How to Observe It — PDF p. 244Views of the Moon through an apochromat are almost completely free of distortion and are of high contrast, rivaling the kind of view to be had through a good-quality long-focal-length Newtonian reflector (see below).
The Moon and How to Observe It — PDF p. 247using reflected light in an optical system, or an automatic response to a stimulus
However, successful lunar photography using an ordinary film camera – be it a simple compact camera or a 35mm SLR (single lens reflex) – is more involved than many imagine.
The Moon and How to Observe It — PDF p. 92SLR Photography SLR (single lens reflex) cameras direct the light from the object being photographed through the main camera lens to the eye via a mirror, prism and eyepiece.
The Moon and How to Observe It — PDF p. 95to bend light as it passes between different materials
These lenses attempt to refract all the wavelengths of light to a focus at a single point. Achromatic objectives do not eliminate chromatic aberration altogether, but, generally speaking, the effects are less noticeable in longer-focal-length refractors.
The Moon and How to Observe It — PDF p. 247The corrector plate is actually aspherical in shape, figured to refract the light onto an internal primary mirror, which reflects light onto the convex secondary mirror, which in turn reflects light back down the tube and through a central hole in the primary mirror into the eyepiece.
The Moon and How to Observe It — PDF p. 249a telescope that forms an image with lenses
Down to the last detail, the Moon that was viewed by Galileo through his tiny refractor in the early 17th Century is probably utterly indistinguishable from the Moon viewed through a 21st-Century telescope eyepiece.
The Moon and How to Observe It — PDF p. 82The scale was devised according to the appearance of a highly magnified star and its surrounding airy pattern through a small refractor.
The Moon and How to Observe It — PDF p. 89to arrange or control in an overly regular manner
Stippling in too regimented a fashion – along straight lines, for example – may give rise to unwelcome artifacts.
The Moon and How to Observe It — PDF p. 88the layer of loose fragmented material covering solid bedrock
All of the loose material that overlies the solid rocky crust of the Moon is named the “regolith, ” and it includes the largest boulders to the finest granules of soil.
The Moon and How to Observe It — PDF p. 24Typical mare regolith consists of a layer of pulverized boulders, rocks and rubble from 2 to 8 meters deep, overlain with a few centimeters of soil.
The Moon and How to Observe It — PDF p. 24continuing without pause or weakening
The Copernican Period now shows the effects of surface erosion by innumerable meteoroids and micrometeoroids – a relentless pummeling that has gradually rounded the lunar hills and produced a layer of fine soil.
The Moon and How to Observe It — PDF p. 21suggesting or reminding one of something else
Mare Humorum’s southeastern border is made up of a prominent range of mountains, the western edge of which, Rupes Kelvin, makes a straight 190-km-long scarp face, interrupted at intervals by small, narrow headlands that jut out into the mare, rather reminiscent of coastal groins.
The Moon and How to Observe It — PDF p. 201a surviving part left after most of something has disappeared
The Moon’s bright highland regions – the shattered, impact-battered remnants of its original crust – are made up of rocks rich in the mineral feldspar, and are generally termed “anorthositic” rocks.
The Moon and How to Observe It — PDF p. 26Low, rounded hills called “domes” – typically a few hundred meters high and with bases several kilometers across – are the remnants of ancient lunar volcanoes, and their tiny summit craterlets represent volcanic vents.
The Moon and How to Observe It — PDF p. 38having a good and trustworthy reputation
As is usually the case, you get what you pay for, but providing they are purchased from a reputable optical dealer, the quality of budget optical instruments these days is usually quite good.
The Moon and How to Observe It — PDF p. 243Any reputable company that specializes in selling and/or manufacturing optical instruments will give by far the best deal in terms of price, service and advice.
The Moon and How to Observe It — PDF p. 245remaining after most of something has gone or been removed
Dust particles should be carefully removed with a soft optical brush or an air puffer, and any residual dirt can be gently removed with optical lens wipes, each used once and applied in a single stroke.
The Moon and How to Observe It — PDF p. 248the delay between successive moonrises, or a slowing or delay more generally
Intervals between the times of successive moonrises each night are called retardations, and they average less than an hour, the Moon rising around 50 minutes later each day.
The Moon and How to Observe It — PDF p. 62The observer’s latitude also plays an important part in how greatly lunar retardation is seen to differ from the norm.
The Moon and How to Observe It — PDF p. 62delayed or occurring later than expected
However, at extremes of libration, Ptolemaeus can lie more than 3° east or west of the mean center of the Moon, and its appearance on the terminator can be advanced by more than 12 hours prior to first quarter or retarded by more than 12 hours after first quarter phase.
The Moon and How to Observe It — PDF p. 91moving or rotating in the direction opposite to the usual or prograde direction
A collision between the embryonic Mercury and Venus may account for their unusual properties – Mercury’s huge iron core and Venus’s slow, retrograde axial rotation.
The Moon and How to Observe It — PDF p. 18The line of nodes rotates (with respect to the stars) in a retrograde fashion every 18.61 years.
The Moon and How to Observe It — PDF p. 53a long, narrow crest of raised ground
Beyond the rim there is a considerable amount of physical structure, including prominent radial ridges and grooves, in addition to secondary cratering caused by the impact of substantial chunks of excavated bedrock.
The Moon and How to Observe It — PDF p. 32A number of mare ridges are the remnants of ancient lava flows; numerous examples can be viewed in Mare Imbrium.
The Moon and How to Observe It — PDF p. 39a long crack or valley formed when crust is pulled apart
By far the biggest lunar graben (far too large to be termed a rille) is Vallis Alpes, a spectacular rift valley that cuts neatly across the lunar Alps.
The Moon and How to Observe It — PDF p. 41Vallis Alpes, a large rift valley in the lunar Alps, was caused when crustal tension caused two parallel faults to appear across the mountains; the crust between the faults subsequently dropped down.
The Moon and How to Observe It — PDF p. 42the state of being stiff or resistant to deformation
This lens focuses light across a chamber filled with vitreous humor, a clear jelly that gives the eyeball its rigidity, and an upside-down image is projected onto the retina inside the back part of the eyeball.
The Moon and How to Observe It — PDF p. 239extremely thorough, careful, and exact
Over the years, there have been occasional claims of the discovery of such wraithlike companions of the Moon, both photographically and visually, but none of these claims have stood up to rigorous examination.
The Moon and How to Observe It — PDF p. 67a long, narrow channel or valley on the lunar surface
Their courses were later exposed when the fragile tunnel roofs collapsed, and the remnants of the original roof can be observed on the rille floor, some large house-sized fragments having survived the fall intact.
The Moon and How to Observe It — PDF p. 40Vallis Schröteri (Schröter’s Valley), the largest lunar sinuous rille, lies on the Aristarchus plateau in Oceanus Procellarum.
The Moon and How to Observe It — PDF p. 40the raised outer edge of a crater or other depression
The material originally nearer the surface is ejected furthest, while deeper bedrock is lobbed shorter distances from the rim.
The Moon and How to Observe It — PDF p. 31Beyond the rim there is a considerable amount of physical structure, including prominent radial ridges and grooves, in addition to secondary cratering caused by the impact of substantial chunks of excavated bedrock.
The Moon and How to Observe It — PDF p. 32a named fissure, groove, or narrow channel on a planetary surface
Rima Hadley, a narrow, sinuous rille 80 km long, can be found cutting across the marial plain at the base of Mons Hadley Delta.
The Moon and How to Observe It — PDF p. 136Somewhat easier to discern is the nearby Rima Bradley (130 km long), which cuts a curving furrow across the hills north of Mons Bradley.
The Moon and How to Observe It — PDF p. 136the plural of rima, used for named grooves or channels on a planetary surface
The best views of the Rimae Posidonius are to be obtained through a 150mm telescope at high magnification.
The Moon and How to Observe It — PDF p. 134In the mountains west of Vallis Alpes are the numerous rilles of Rimae Plato, thought to have been cut by lava flows just like Vallis Alpes’ medial rille.
The Moon and How to Observe It — PDF p. 145strong, durable, and able to withstand damage
They are usually far less expensive, are easier to carry around (even with a stand), deliver a wide field of vision and are more robust than telescopes, capable of withstanding occasional knocks.
The Moon and How to Observe It — PDF p. 241to turn about an axis or central point
The line of apsides rotates (with respect to the stars) in a prograde fashion every 8.85 years.
The Moon and How to Observe It — PDF p. 53The line of nodes rotates (with respect to the stars) in a retrograde fashion every 18.61 years.
The Moon and How to Observe It — PDF p. 53the turning of a body about its own axis
Because the inner regions of the protoplanet became more massive, there was a gradual acceleration in its axial rotation, and centrifugal forces gave rise a pronounced equatorial bulge.
The Moon and How to Observe It — PDF p. 13Tidal forces have the net effect of slowing the Earth’s rotation by a tiny fraction of a second every century, and, in the same period, the Moon recedes from the Earth by several meters.
The Moon and How to Observe It — PDF p. 14broken stones, rocks, or building material
Typical mare regolith consists of a layer of pulverized boulders, rocks and rubble from 2 to 8 meters deep, overlain with a few centimeters of soil.
The Moon and How to Observe It — PDF p. 24Biela C (28 km), superimposed upon Biela’s northeastern rim, is noteworthy because of its floor, piled high with masses of rubble.
The Moon and How to Observe It — PDF p. 229a named escarpment or cliff in planetary nomenclature
Easily the best example of a normal fault on the Moon is Rupes Recta (often called “the ‘Straight Wall”) in southeastern Mare Nubium.
The Moon and How to Observe It — PDF p. 41Faults that have been produced in the lunar highlands tend not to have the clean-cut form of Rupes Recta.
The Moon and How to Observe It — PDF p. 41a steep slope or cliff produced by faulting or erosion
At sunrise, binoculars and small telescopes will reveal Rupes Recta’s broad black shadow, but the bright scarp face itself, illuminated by an evening Sun, represents something of a challenge.
The Moon and How to Observe It — PDF p. 125Rupes Recta (Straight Scarp) is a 110-km-long normal fault in eastern Mare Nubium caused by crustal tension.
The Moon and How to Observe It — PDF p. 125a proposed sequence of events or possible situation
In the capture scenario, gravitational perturbations caused the orbit of an inner planet to become so eccentric that it came within the range of capture by the Earth.
The Moon and How to Observe It — PDF p. 16This scenario would explain the elongated shapes of the pair and their unique pattern of ejecta.
The Moon and How to Observe It — PDF p. 224to mix or throw into a confused or irregular arrangement
West of Gambart, up to Reinhold (48 km), a scrambled mass of hills rises from the patchy mare.
The Moon and How to Observe It — PDF p. 161to examine very closely and carefully
Nearby, the area around the sharp, bowl-shaped crater Cauchy (12 km) makes a most interesting area to scrutinize at high magnification when illuminated by a low Sun.
The Moon and How to Observe It — PDF p. 152This means frequent adjustments to the mount if the Moon is to be scrutinized for any length of time.
The Moon and How to Observe It — PDF p. 242careful and detailed examination
Closer scrutiny will reveal that more than a dozen different types of terrain exist on Mercury.
The Moon and How to Observe It — PDF p. 69Close telescopic scrutiny will reveal that, like Posidonius, Chacornac has an off-center bowl-shaped crater and a system of small rilles that bisect its floor.
The Moon and How to Observe It — PDF p. 134describing a long-term, nonperiodic astronomical change
The rate of change in the Earth’s secular rotation actually amounts to just 2.3 milliseconds per century (23 seconds every million years), large enough to be measured against atomic clocks.
The Moon and How to Observe It — PDF p. 54In addition to the slow advance of the line of apsides, the other major secular perturbation is seen in the recession of the line of nodes (the line joining the ascending and descending nodes, as described above), which moves westwards along the ecliptic by 1.6° each month.
The Moon and How to Observe It — PDF p. 55relating to vibrations or waves travelling through a planetary body
Long time delays in the arrival of seismic waves also suggest that the lunar crust is highly fractured and faulted.
The Moon and How to Observe It — PDF p. 21Seismic measurements have given tantalizing clues as to the internal construction of our satellite.
The Moon and How to Observe It — PDF p. 21relating to the mapping or physical description of the Moon
Selenographic Coordinates Coordinates on the Moon are termed “selenographic coordinates. ” The mean center of the lunar disc is located at a selenographic latitude of 0° and a selenographic longitude of 0°.
The Moon and How to Observe It — PDF p. 90A feature’s selenographic coordinates can be indicated on the observational drawing.
The Moon and How to Observe It — PDF p. 91the mapping and description of the Moon’s surface
Just as geography is concerned with mapping of the Earth, so selenography deals with practical mapping of the Moon.
Atlas of the Moon — PDF p. 11the scientific study of the Moon's geology and physical features
The ALS has a great quarterly journal, Selenology, that features Moon-related articles and observations.
The Moon and How to Observe It — PDF p. 268designed to excite strong interest through exaggerated claims
It is not advisable to buy a new telescope from any source other than a reputable telescope dealer, and I recommend that sensational newspaper advertisements, department stores and general electrical stores ought to be avoided.
The Moon and How to Observe It — PDF p. 245a narrow beam or column of light
Another solar eclipse spectacle is Baily’s Beads, a phenomenon caused by shafts of sunlight shining though lunar valleys at its limb, which gives the impression of a diamond-studded necklace.
The Moon and How to Observe It — PDF p. 65In the morning, while the western flanks of Plato remain in shadow, joined with the terminator, its inner western wall and the western part of its floor are illuminated by shafts of sunlight streaming through low points in the crater’s eastern rim.
The Moon and How to Observe It — PDF p. 166having a crisp, sharply defined raised edge
Small, bright, sharp-rimmed crater west of Mare Crisium, the centre of a prominent asymmetrical ray system arranged in a broad fan shape.
The Moon and How to Observe It — PDF p. 122A highly eroded, irregular crater,de la Rue (136 km), at the far eastern end of the mare, contrasts with the sharp-rimmed craters Strabo (55 km) and Thales (32 km) that adjoin it.
The Moon and How to Observe It — PDF p. 142to break violently into many pieces
Breccia is a composite rock made up of fragments created through the processes of impact shattering, mixing, melting and recrystallization of rock during the high energies released during meteoroid and asteroid impacts.
The Moon and How to Observe It — PDF p. 26An impact of the same magnitude as the one that excavated the Moon’s Imbrium basin around 3 billion years ago would have easily shattered the young Earth’s thin crust and stimulated large-scale vulcanism.
The Moon and How to Observe It — PDF p. 72a broad, gently sloping volcano built by repeated fluid lava flows
The Tharsis area is the most spectacular of Mars’s volcanic regions, boasting four major volcanic shields that sprawl across the landscape.
The Moon and How to Observe It — PDF p. 74Most domes are volcanic features built up by successive eruptions of lava that may have had a viscosity equivalent to that which formed (and is still forming) the Hawaiian shield volcanoes on Earth.
The Moon and How to Observe It — PDF p. 118the boundary where a body of water or a plain described as a sea meets land or higher terrain
A small, well-defined circular sea, its southern shoreline dented by the large bay crater Fracastorius (124 km).
The Moon and How to Observe It — PDF p. 115On the northern shoreline of Mare Frigoris, due north of Plato (see Area Six) is the irregularly shaped, disintegrated crater Birmingham (92 km), a feature with low, roughly hewn walls, identifiable under a low illumination.
The Moon and How to Observe It — PDF p. 141a brief system or method used to record information quickly
Many observers choose to make annotated line drawings at the eyepiece, using the technique as a form of observational shorthand, along with intensity estimations (see below).
The Moon and How to Observe It — PDF p. 85To make the task manageable, an intensity-estimates shorthand is used to accompany line drawings.
The Moon and How to Observe It — PDF p. 86measured relative to the distant stars
Measured with respect to the stars, the Moon takes 27d 7h 43m to make one revolution around the Earth, a period called the sidereal orbital period.
The Moon and How to Observe It — PDF p. 52A telescope that drives at a sidereal rate, suitable for general astronomical observation, will not keep the Moon centered with high accuracy, and it will require occasional adjustment.
The Moon and How to Observe It — PDF p. 255to mean, indicate, or represent
For example, 30°W signifies 30° of western selenographic longitude, which could also be written as λ = −30°.
Atlas of the Moon — PDF p. 11occurring or existing at the same time
Another theory of the simultaneous formation of the Earth, Moon and Mars envisions a rapidly spinning twin-lobed proto-planet; the massive central hub became Earth, while the lobes were flung off to form the Moon and Mars.
The Moon and How to Observe It — PDF p. 14having many smooth curves or bends
Such are the dynamics of impact that these radial structures do not follow perfectly straight lines – secondary-chain craters can follow quite curved, even sinuous, paths over the surface.
The Moon and How to Observe It — PDF p. 32Formed by fast- flowing lava, Sinuous rilles originate at volcanic vents and meander downslope.
The Moon and How to Observe It — PDF p. 39a bay-like dark plain in lunar nomenclature
One of the more unusual of the Moon’s rilles is the Hyginus rille in Sinus Medii, a valley 220 km in length that is punctuated by a series of small craters, including Hyginus itself.
The Moon and How to Observe It — PDF p. 42to turn or move rapidly toward a new direction or target
A computerized telescope can automatically slew to the position of the Moon and track it accurately at the touch of a button, and basic lunar information can be displayed on the keypad’s viewscreen.
The Moon and How to Observe It — PDF p. 256When details of the observing location and the exact time are input, a computerized telescope can automatically slew to the position of any celestial object above the horizon at the touch of a few buttons on a keypad.
The Moon and How to Observe It — PDF p. 256a very narrow or thin visible piece
While the inner western wall is presented very favorably, our view from an angle of about 42° above the crater means that (when it is illuminated by the Sun) its inner eastern wall appears as a narrow sliver.
The Moon and How to Observe It — PDF p. 170The feature is not at all visible when there is a libration favoring the Moon’s eastern limb, and even when libration favors the southwestern limb, a good libration of around 7° when the Moon is past full phase is needed in order to view the whole of the mare as a thin, dark sliver near the edge of the Moon.
The Moon and How to Observe It — PDF p. 58to slide or collapse downward, or a mass that has done so
The feature settles and collapses along points of crustal weakness, giving rise to slumping and internal terracing of the walls.
The Moon and How to Observe It — PDF p. 31Around the edge of the floor can be resolved piles of material that have slumped from the inner wall.
The Moon and How to Observe It — PDF p. 165completely covered by a layer of material
Surrounding Aristarchus (with the exception of its western flanks) is a dark collar extending about 25 km from the crater’s rim, representing an area that has been smothered by dark, glassy impact melt.
The Moon and How to Observe It — PDF p. 171Cardanus is smothered with ray material from Olbers A, 190 km to the south, and it is among this ray material that Rima Cardanus can be found; this is a narrow rille that cuts 120 km from the uplands and across the mare southeast of Cardanus.
The Moon and How to Observe It — PDF p. 173a slow-moving mollusk with a spiral shell, used here in a feature nickname
This feature is known unofficially as “Schneckenberg” (Snail Mountain), owing to its alleged spiral structure, rendered visible only at low angles of illumination.
The Moon and How to Observe It — PDF p. 137to make someone serious and thoughtful
It is sobering to realize that many of the lunar features visible through the telescope have been preserved intact from eons before the sketchy knowledge of our own planet’s history begins.
The Moon and How to Observe It — PDF p. 72the chemical element with atomic number 11
Those living near sodium streetlighting will be able to perform another experiment, this time illustrating a psychological aspect of human color perception.
The Moon and How to Observe It — PDF p. 109Therefore, we perceive our sodium orange surroundings as being illuminated with white light, and the blueness of the shadow is simply caused by color contrast perception – an effect obvious in double stars like Albireo (Beta Cygni), whose brighter yellow component much enhances the blueness of its companion.
The Moon and How to Observe It — PDF p. 109existing alone or apart from others
A solitary central peak, Alphonsus Alpha (3,000 m high, with a base diameter of 10 km) rises at the center of a flooded floor that lies some 2,730 m beneath the surrounding highlands; Alphonsus is therefore a few hundred meters deeper than its neighbor, Ptolemaeus.
The Moon and How to Observe It — PDF p. 207either annual point when the Sun reaches its greatest north or south declination
At summer solstice, the midday Sun reaches its highest point above the southern horizon, and the full Moon appears very low near the southern horizon at midnight.
The Moon and How to Observe It — PDF p. 61At summer solstice, the Sun reaches its highest point above the horizon, whereas the mid-summer full Moon just manages to pull itself clear of the southern horizon for a few hours (as seen from northern temperate latitudes such as the U.K., the northern U.S. and southern Canada).
The Moon and How to Observe It — PDF p. 109an impressive or striking sight
Another solar eclipse spectacle is Baily’s Beads, a phenomenon caused by shafts of sunlight shining though lunar valleys at its limb, which gives the impression of a diamond-studded necklace.
The Moon and How to Observe It — PDF p. 65When Mare Crisium is fully exposed to the morning sunshine a day later, it makes a grand spectacle through any instrument.
The Moon and How to Observe It — PDF p. 150strikingly impressive or dramatic
The Marius hills in Oceanus Procellarum create one of the Moon’s most spectacular volcanic landscapes: no fewer than a hundred volcanic cones and domes occupying an area of around 40,000 sq km.
The Moon and How to Observe It — PDF p. 39By far the biggest lunar graben (far too large to be termed a rille) is Vallis Alpes, a spectacular rift valley that cuts neatly across the lunar Alps.
The Moon and How to Observe It — PDF p. 41relating to a spectrum or its component wavelengths
Since spectral analysis shows that these dark halos consist of mare basalt, these dark-haloed impact craters provide evidence for ancient buried lava plains known as cryptomaria.
The Moon and How to Observe It — PDF p. 38an instrument that separates light into a spectrum for analysis
Few amateurs have been able to secure a photographic record of TLP , let alone employ anything as sophisticated as a spectroscope during these events when they have occurred.
The Moon and How to Observe It — PDF p. 44How could a spectroscope that is pointed directly towards the surface of the lifeless Moon possibly detect water, molecular oxygen and chlorophyll, the latter indicating the presence of land plants?
The Moon and How to Observe It — PDF p. 60the study of matter or radiation by measuring its spectrum
Observations from lunar orbit using neutron spectroscopy (which detects certain types of neutrons emitted by hydrogen atoms) have revealed that the water ice signature is stronger at the Moon’s north pole than at the south pole (a signature of 4.6% compared with 3%).
The Moon and How to Observe It — PDF p. 43a range of electromagnetic wavelengths or a continuous range of related values
These substances can actually be detected by analyzing the spectrum of sunlight that has been reflected from the Earth onto the Moon and back to the Earth.
The Moon and How to Observe It — PDF p. 60Both of these activities, lying at opposite ends of the lunar observing spectrum, aim to answer scientific questions.
The Moon and How to Observe It — PDF p. 82a support with thin arms that holds a telescope’s secondary mirror
Vibration or a slight, sudden knock to the tube can cause misalignment of the primary mirror in its cell or the secondary in its spider.
The Moon and How to Observe It — PDF p. 248The most popular reflecting telescope design, the Newtonian, uses a concave primary mirror held in a cell at the bottom of the tube and a smaller flat secondary mirror mounted on a “spider” near the top of the tube, which reflects light sideways through the tube into the eyepiece.
The Moon and How to Observe It — PDF p. 248a long, narrow central ridge or line of peaks
Montes Caucasus (see Area One), a prominent spine of mountains, stretches for 500 km southwards from the vicinity of Eudoxus to mark part of the far-eastern border of Mare Imbrium.
The Moon and How to Observe It — PDF p. 145Montes Riphaeus, a substantial mountain spine, rises at the junction between Mare Cognitum and Oceanus Procellarum.
The Moon and How to Observe It — PDF p. 179curving continuously around a central point while moving toward or away from it
This feature is known unofficially as “Schneckenberg” (Snail Mountain), owing to its alleged spiral structure, rendered visible only at low angles of illumination.
The Moon and How to Observe It — PDF p. 137to spread over a large area in an irregular way
Hot spots in the mantle have punctured the planet’s relatively static crust and allowed huge accumulations of material to extrude onto the surface and sprawl across the local terrain.
The Moon and How to Observe It — PDF p. 72The Tharsis area is the most spectacular of Mars’s volcanic regions, boasting four major volcanic shields that sprawl across the landscape.
The Moon and How to Observe It — PDF p. 74false, misleading, or not genuinely caused by what it appears to indicate
Advocates of lunar change, attempting to establish a degree of respectability in their field, have been unfortunately hindered by the opinions of cranks and the spurious observations of charlatans.
The Moon and How to Observe It — PDF p. 47Too much image processing and unsharp masking may produce spurious artifacts in the image’s texture and a progressive loss of tonal detail.
The Moon and How to Observe It — PDF p. 104a small viewing hole used to align or sight an object
At apogee the slider will be around 94 cm from the squint hole.
The Moon and How to Observe It — PDF p. 108With the staff resting on a solid surface (say, a garden fence or a camera tripod) the Moon is sighted through the squint hole and aligned between the pins on the slider.
The Moon and How to Observe It — PDF p. 108to arrange unevenly or to amaze greatly
Fading or staggered effects in an occulted star’s light may suggest the presence of a previously unsuspected companion (or companions) to that star.
The Moon and How to Observe It — PDF p. 67Southeast of Mare Nectaris, one of the Moon’s most spectacular fault features, Rupes Altai (Altai Scarp) presents a curving, scalloped cliff of staggering proportions – almost 500 km long, running from west of the crater Catharina to Piccolomini.
The Moon and How to Observe It — PDF p. 125a point of view or way of considering something
Partial lunar eclipses are more satisfying from an observational stance.
The Moon and How to Observe It — PDF p. 126severe, sharply defined, or strikingly plain
Flatter areas that present a smooth shallow angle to the Sun, such as the marial plains, do not show such a stark contrast of light and dark at the terminator.
The Moon and How to Observe It — PDF p. 62The Moon’s surface bears stark testimony to eons of impact.
The Moon and How to Observe It — PDF p. 28not moving or changing
Hard photographic evidence from cameras in lunar orbit shows that things aren’t altogether static on the Moon’s surface.
The Moon and How to Observe It — PDF p. 48The Moon has a relatively thick, static crust and a warm interior, with a very small core.
The Moon and How to Observe It — PDF p. 50relating to stars
Stellar occultation studies are important because they are an accurate means of determining the Moon’s motion with respect to the background stars.
The Moon and How to Observe It — PDF p. 67relating to a map projection from a sphere onto a plane
The sectors close to the poles are mapped in stereographic projection, while the sectors close to the equator are drawn in Mercator projection.
Atlas of the Moon — PDF p. 93drawn or shaded with many small dots
Being composed of thousands of individually applied black dots, stippled drawings reproduce very nicely even when they are photocopied.
The Moon and How to Observe It — PDF p. 87a drawing or shading technique that builds tone from many small dots
An individual capable of producing wonderful pencil drawings may not necessarily be able to master stippling.
The Moon and How to Observe It — PDF p. 87Ink stippling is one method of reproducing observational drawings that looks absolutely superb when done skillfully.
The Moon and How to Observe It — PDF p. 87a narrow passage connecting two larger bodies or areas
This mountain range, named by Mädler, is a direct continuation of the lunar Apennines, from which the Caucasus are separated by a 50-km-wide ‘strait’ between Mare Imbrium and Mare Serenitatis.
Atlas of the Moon — PDF p. 29The length of the Caucasus is about 520 km and the mountain range extends from the strait (in the bottom left-hand corner of map 13) to the crater Eudoxus.
Atlas of the Moon — PDF p. 29unwanted and travelling away from the intended optical path
The optical surfaces are usually multicoated to minimize reflections, and internal baffles block stray light and internal reflections, providing better contrast.
The Moon and How to Observe It — PDF p. 243a long, narrow line or mark different in color or brightness from its surroundings
Dione, 1,100 km across, is smaller than Rhea, but the two satellites are similar in appearance, with many impact craters and light streaks feathering their surfaces.
The Moon and How to Observe It — PDF p. 78Some areas of the surface are mottled with light, wispy streaks, superficially resembling lunar rays, but their origin is probably internal, having resulted from the intrusion of ice along fissures in the crust.
The Moon and How to Observe It — PDF p. 78to shape or smooth by the action of flowing material
Another unique feature is the streamlining of landscape around craters and other areas of pronounced relief, which indicates extensive water flow in Mars’s history.
The Moon and How to Observe It — PDF p. 74marked with parallel lines, grooves, or ridges
Parts of the planet are striated by parallel linear rilles comparable to the rilles found in many parts of the Moon.
The Moon and How to Observe It — PDF p. 72Much of the Apennine range is striated in a pattern radial to Mare Imbrium, somewhat resembling the effects of glaciation.
The Moon and How to Observe It — PDF p. 116to astonish or impress intensely
Clavius (225 km), a giant crater that is absolutely stunning to behold through any-sized telescope, is the chief topographic attraction of the Moon’s southern uplands.
The Moon and How to Observe It — PDF p. 191One of the main reasons that people buy their first telescope is to see detail on the Moon – indeed, advertisements for many entry-level instruments play on this fact by including stunning images of the lunar surface.
The Moon and How to Observe It — PDF p. 245strong, stable, and not easily shaken or damaged
High-magnification with undriven telescopes also demands a sturdy mount that does not shake unduly when pushed, and smooth bearings that respond to light touch and produce little backlash – qualities found in only the best altazimuth and Dobsonian mountings.
The Moon and How to Observe It — PDF p. 255situated or originating beneath a planet's or moon's crust
Earth Elements, and Phosphorus), represents the last vestiges of the Moon’s subcrustal magma ocean and was formed on the border of the crust and mantle.
The Moon and How to Observe It — PDF p. 19Because Europa is warm inside, with subcrustal oceans of liquid water, there is an outside possibility that some form of primitive marine life may have developed in this lonely outpost.
The Moon and How to Observe It — PDF p. 77reduced in prominence, brightness, or relief
What appears to be a flat floor is covered with numerous small simple craters and with old, subdued craters or shallow circular depressions, which are visible only under low illumination.
Atlas of the Moon — PDF p. 100to put or pass beneath a liquid or covering material
There are no traces of the crater’s original central elevations, as they have been completely submerged by lava flows.
The Moon and How to Observe It — PDF p. 165Sinus Iridum is an impact basin that has been flooded with lava, completely submerging half its wall.
The Moon and How to Observe It — PDF p. 167secondary or less important than the main thing
In 1935 the so-called subsidiary craters had been designated by using the capital letters of the Latin alphabet; for example, Mösting A was associated with the larger crater, Mösting.
Atlas of the Moon — PDF p. 12The adjacent letter, designating a subsidiary small crater, is printed on the side nearest to the primary crater from which it derives its name.
Atlas of the Moon — PDF p. 16delicate or difficult to notice or distinguish
But, as the major landmarks are noted, they can be used as stepping stones to hop across to other, more subtle, features that may have originally been overlooked.
The Moon and How to Observe It — PDF p. 83This difference in the Moon’s apparent diameter is far too subtle to be detected with the naked eye, as it amounts to around 1 minute of arc at maximum.
The Moon and How to Observe It — PDF p. 107a fine distinction or delicate feature that is difficult to notice
I would recommend that lunar eclipses be viewed through binoculars rather than through a single telescope eyepiece; using both eyes adds to the observer’s enjoyment, the subtleties of the colors in the umbral shadow stand out more, and the sight of the eclipsed Moon set against the stars can appear almost 3-dimensional when viewed with two eyes.
The Moon and How to Observe It — PDF p. 242a set of related tools or programs used together
Designed to help lunar observers plan and record the Moon, this popular program has a comprehensive suite of handy tools.
The Moon and How to Observe It — PDF p. 269the chemical element with atomic number 16
Io is a rocky world, composed of silicates and sulfur.
The Moon and How to Observe It — PDF p. 77placed or formed over something else
Narrower dorsa with slopes of about 15° can often be seen lying parallel to, or even superimposed upon, the broad ridges.
The Moon and How to Observe It — PDF p. 39Low illumination will reveal that Philolaus is superimposed upon a larger, more ancient and eroded crater to its southwest.
The Moon and How to Observe It — PDF p. 164easily affected, damaged, or changed by something
German-style Porro prism binoculars feature objective housings that screw into the main body containing the prisms; their modular nature makes them more susceptible to going out of collimation after knocks.
The Moon and How to Observe It — PDF p. 243to exchange one thing for another
The use of two premium zoom eyepieces will prevent having to swap eyepieces to alter the magnification.
The Moon and How to Observe It — PDF p. 254a curved or twisted pattern resembling a vortex
It is the near side’s best example of a swirl (see Chapter One).
The Moon and How to Observe It — PDF p. 176To its southwest is the enigmatic bright swirl, Reiner Gamma.
The Moon and How to Observe It — PDF p. 169occurring at the same rate, especially rotation matching orbital revolution
Locked in a synchronous rotation, the Moon keeps the same face turned in the Earth’s direction as it orbits.
The Moon and How to Observe It — PDF p. 55relating to the interval between successive similar alignments or phases of celestial bodies
Every 29.5 days it goes through a complete cycle of phases, waxing from new Moon to full Moon and waning to new Moon once more, the synodic month, or lunation.
The Moon and How to Observe It — PDF p. 61In 29.5 days it goes through a complete set of phases, from new Moon, through full Moon and back to new Moon again; this period is called a synodic month, or lunation.
The Moon and How to Observe It — PDF p. 108an alignment of three celestial bodies, especially the Sun, Earth, and Moon
At syzygy, the Sun’s gravitational attraction complements that of the Moon, producing the most pronounced tidal bulges.
The Moon and How to Observe It — PDF p. 54When the Moon is near new or full phase, the Earth, Moon and Sun are aligned – a phenomenon known as syzygy.
The Moon and How to Observe It — PDF p. 54a straight line touching a curve at one point
Such observations are best made during grazing occultations, when the limb of the Moon just touches the star at maximum occultation and the star appears to graze along at a tangent to the lunar disc.
The Moon and How to Observe It — PDF p. 67to draw out or reveal something difficult to perceive
By paying full attention to a small area of the Moon, instead of allowing the eye to roam around the lunar surface, the brain begins to make sense out of the light and shade, teasing fine topographic detail from what may have initially looked like a plain hole in the ground.
The Moon and How to Observe It — PDF p. 83relating to deformation or movement of a planetary crust
Because there has been no lunar tectonic activity or large-scale crustal movement, metamorphic rocks such as schist and gneiss, formed slowly through crustal pressure and heat, are not found on the Moon.
The Moon and How to Observe It — PDF p. 25The Moon’s small size, its lack of a dynamic interior and the relatively great thickness of its crust ruled out all possibility of plate tectonics.
The Moon and How to Observe It — PDF p. 42having or using a long focal length for a narrow, enlarged view
A larger telephoto lens will need to be attached to an equatorially driven mount, either directly or riding piggyback on a driven telescope.
The Moon and How to Observe It — PDF p. 96A tripod-mounted SLR and a telephoto lens with a focal length from 800 to 2,000mm will deliver the best telephoto lunar photographs.
The Moon and How to Observe It — PDF p. 96relating to regions between tropical and polar zones, with generally moderate conditions
From southern temperate latitudes, the full Moon appears very low above the northern horizon during December.
The Moon and How to Observe It — PDF p. 53For observers in temperate latitudes, the range of lunar retardation is far greater, from a few minutes up to as much as an hour and a half.
The Moon and How to Observe It — PDF p. 63to attract or persuade someone toward an action
Copernicus is so overwhelmingly spectacular that the observer is tempted to linger over it for hours on end, but it is worthwhile paying closer scrutiny to these least obvious attractions of the region.
The Moon and How to Observe It — PDF p. 162Some viewers of the Moon are tempted to seek the best of both worlds by having the convenience of binoculars with a zoom facility.
The Moon and How to Observe It — PDF p. 242to end or come to an endpoint
The terminator is the line that divides the object’s sunlit side from its dark side – literally, the line where sunlight terminates.
The Moon and How to Observe It — PDF p. 62One can trace prominent rille running from these hills across the crater wall to the center of Fra Mauro, terminating at the little crater Fra Mauro E (4 km).
The Moon and How to Observe It — PDF p. 181the boundary between the illuminated and dark hemispheres of a celestial body
Conversely, some albedo features are quite invisible when near the morning or evening terminator, but stand out boldly under a high Sun.
The Moon and How to Observe It — PDF p. 45However, libration can cause Ptolemaeus to appear on the morning terminator of a distinctly crescent Moon, as well as on a considerably gibbous Moon.
The Moon and How to Observe It — PDF p. 59a step-like bench on a slope or crater wall
It has a sharp rim, wide internal walls with prominent terracing and a large group of central peaks that rise above a flattish floor filled with breccia and impact melt.
The Moon and How to Observe It — PDF p. 34It has broad terraced walls and an impact-melt floor with a substantial, near-complete inner ring of mountains, but no central elevations.
The Moon and How to Observe It — PDF p. 34a region of ground considered in terms of its physical features
Some of this structure may be caused by elevations in the surrounding terrain that leave a “bow wave” pattern free of ejected debris.
The Moon and How to Observe It — PDF p. 32The concentration of these seismic waves led to the formation of localized areas of chaotic terrain, where pre-existing structures were shaken to their foundations, producing a knobbly, textured landscape.
The Moon and How to Observe It — PDF p. 37relating to Earth or to rocky Earth-like planets
The early Solar System saw countless major impacts, and the evidence can be readily observed in the impact scars of the terrestrial planets and the satellites.
The Moon and How to Observe It — PDF p. 18All of the terrestrial planets – Mercury, Venus, Mars and the Earth – are thought to have been subjected to similar levels of bombardment, but only Mercury’s surface resembles that of the Moon.
The Moon and How to Observe It — PDF p. 27to provide evidence or confirmation from experience
They provide a good example of how the appearance of a lunar feature can alter considerably during a lunar day because of the changing angle of illumination, as anyone who has observed them under a variety of lighting conditions can testify.
The Moon and How to Observe It — PDF p. 48clear evidence or proof of something
The Moon’s surface bears stark testimony to eons of impact.
The Moon and How to Observe It — PDF p. 28the visual or physical character of a surface
Their surroundings are mottled with a peculiar “herringbone texture” made up of a mass of V-shaped hummocks that point towards the crater.
The Moon and How to Observe It — PDF p. 32The satellite’s very rough surface texture suggests that recent crustal heating and melting is unlikely to have taken place.
The Moon and How to Observe It — PDF p. 79relating to heat
It has been suggested that the thermal shock due to the lunar rocks’ expanding as they heat up (and contracting as they cool down) may be a cause of TLP.
The Moon and How to Observe It — PDF p. 47The processes of thermal shock, restricted to the materials in the very top layers of the regolith, cannot possibly give rise to any effects observable from the Earth.
The Moon and How to Observe It — PDF p. 47light emitted by a material when heating releases previously trapped energy
Thermoluminescence is caused when certain crystalline materials emit light when they are heated (as excited electrons fall back to their ground state), but the amount of light given off by lunar thermoluminescence is entirely incapable of being detected by amateur instruments, and the process certainly would not explain any reported TLP.
The Moon and How to Observe It — PDF p. 45to excite or delight strongly
It’s thrilling to view the lunar surface through an eyepiece whose apparent field of 60°, 70° or 80° or greater cannot all be taken in by the eye at once.
The Moon and How to Observe It — PDF p. 252Copernicus and its environs are thrilling to observe, and the bright rays that spread in all directions from it can be resolved into a complex series of radial rays that extend in all directions for more than 800 km over the surrounding regions.
The Moon and How to Observe It — PDF p. 121an inclination from a reference direction, or to move into such an inclination
But the lunar poles are actually tilted 6.4° to its orbital plane, and the axial tilt remains fixed in one direction in space.
The Moon and How to Observe It — PDF p. 57The telescope is slung between the arms of the fork, and the base is tilted to point to the celestial pole.
The Moon and How to Observe It — PDF p. 255relating to gradations of light and dark
However, line drawing should not be considered a quick and easy alternative to tonal drawing, since a line drawing ought to be drawn just as carefully, with the same amount of attention to detail.
The Moon and How to Observe It — PDF p. 85The line drawings, and the written information that accompanies them, are then converted into full tonal renditions in pencil or ink after the observing session.
The Moon and How to Observe It — PDF p. 85relating to the shape and relief of a surface
The Orientale impact, just past the southwestern lunar limb, appears to have created a similar topographic disturbance in the region south of the crater Hubble, visible near the Moon’s northeastern limb.
The Moon and How to Observe It — PDF p. 37Wrinkle ridges have a number of possible modes of formation, including mare contraction, topographic moulding to underlying features and vulcanism.
The Moon and How to Observe It — PDF p. 40the arrangement and relief of physical surface features
Achromatic refractors introduce a degree of false color, not usually a problem when the observer is studying topography alone, but distracting if a TLP search is being attempted.
The Moon and How to Observe It — PDF p. 45An elite few of the Solar System’s solid worlds have thick atmospheres capable of adding new dimensions to their surface topography by wind denudation, water erosion and sedimentation.
The Moon and How to Observe It — PDF p. 69the phase of an eclipse during which one body is completely obscured
During totality, the brighter stars and planets become easily visible, even those that lie in the vicinity of the Sun.
The Moon and How to Observe It — PDF p. 65At totality, although the Moon is completely covered by the Earth’s shadow, it never vanishes from view altogether because a certain amount of sunlight is refracted onto the lunar surface through the Earth’s atmosphere.
The Moon and How to Observe It — PDF p. 126a continuous area or stretch of land or surface
Large tracts of the lunar surface have been modified by volcanic activity and other geological processes, including faulting.
The Moon and How to Observe It — PDF p. 28The dark areas of Mars mainly occupy its southern hemisphere in a near-continuous tract encircling the planet.
The Moon and How to Observe It — PDF p. 74a state of calm and quiet
Gone are the days when our own little corner of the Universe was viewed as a place of eternal tranquility, save for the occasional cometary visitor.
The Moon and How to Observe It — PDF p. 18The site has been named Statio Tranquillitatis (Tranquility Base) and three very small craters, Aldrin (3.4 km), Collins (2.4 km) and Armstrong (4.6 km), lie just to its north; they require at least a 150mm telescope to resolve.
The Moon and How to Observe It — PDF p. 139lasting for only a short time
These changes are known as TLP (transient lunar phenomena) and reportedly take the form of localised flashes, glows, obscurations, darkenings and changes of color that take place on a temporary and rather unpredictable basis.
The Moon and How to Observe It — PDF p. 232Blinking Moon A number of observers employ colored filters to determine anomalous red- or blue-colored transient events on the Moon.
The Moon and How to Observe It — PDF p. 233a semiconductor device used to switch or amplify electronic signals
Thin-film transistor (TFT) screens are usually on the small side, and the display is coarser than the captured image itself.
The Moon and How to Observe It — PDF p. 100a change or passage from one state, form, or region to another
There is a sharp transition between the smooth plains bounded by the Cordilleras and the radially grooved, mountainous landscape beyond.
The Moon and How to Observe It — PDF p. 43to cross or extend across an area
Some clefts, such as Asterius Linea, traverse the surface for many hundreds of kilometers.
The Moon and How to Observe It — PDF p. 77This is an illusion, since the ray in question actually emanates from Menelaus on the mare’s southern shore (see Area One), although some of Tycho’s rays can be traced in the area south of Mare Serenitatis, and some ray material does appear to traverse the dark plains of Mare Nectaris (see Area Fifteen), 1,300 km from Tycho.
The Moon and How to Observe It — PDF p. 190a long, narrow, deep depression or channel
The plateau is split by the enormous trench of Diana Chasma, which is 280 km wide and 4 km deep in places.
The Moon and How to Observe It — PDF p. 71The northern part of Maurolycus’s floor is hilly and peppered with small craters, and a ragged group of mountains cut through by a broad and deep curving trench lies just north of center.
The Moon and How to Observe It — PDF p. 217relating to electric charge produced by friction between materials
Triboelectric lightning flashes only occur in high-pressure environments (such as the Earth’s atmosphere); any triboelectric lunar glows would be far too feeble to be discerned from the Earth.
The Moon and How to Observe It — PDF p. 47Within the dust cloud, a triboelectric charge is built up as the particles rub against each other, and lightning occurs when there are triboelectric discharges.
The Moon and How to Observe It — PDF p. 47relating to trigonometry and calculations with angles and triangles
This calculation above is, of course, the most simple means of gauging a feature’s height by trigonometrical means.
The Moon and How to Observe It — PDF p. 238one million million, or 10 to the power of 12
It has been estimated that around 3 trillion craters over a meter in diameter dot the lunar surface.
The Moon and How to Observe It — PDF p. 28However, the Moon has a mass of 73,500 trillion tons, which amounts to just 1.2% the mass of the Earth.
The Moon and How to Observe It — PDF p. 51a group of three related objects or people
Due west of Aristarchus, a trio of very large flooded craters, Eddington (125 km), Struve (170 km) and Russell (103 km), dominate the near-limb region of the far western reaches of Oceanus Procellarum.
The Moon and How to Observe It — PDF p. 173The prominent joined trio of craters, Fra Mauro, Bonpland and Parry, are among the flooded features in northern Mare Nubium.
The Moon and How to Observe It — PDF p. 179a three-legged stand used to support a camera or optical instrument
It may be better to attach the telescope to a good-quality camera tripod.
The Moon and How to Observe It — PDF p. 254To discern fine lunar detail it is important to hold binoculars as steady as possible, either propped up firmly against a solid object (like a car roof) or, better still, fixed to a tripod or a dedicated binocular mount.
The Moon and How to Observe It — PDF p. 241to pull with force, or a pulling force
The additional gravitational attraction of this displaced tidal bulge actually tugs on the Moon and imparts angular momentum to it.
The Moon and How to Observe It — PDF p. 54Moreover, the orbital dynamics of the Earth–Moon system do not square in the coaccretion theory – if the Moon had formed in close proximity to the Earth, its orbit would have initially been equatorial, later conforming to the plane of the ecliptic as a result of the gravitational tug of the Sun.
The Moon and How to Observe It — PDF p. 15to fall or roll suddenly and repeatedly
Using photographs alone, it is impossible to determine the precise date on which the boulders made their short journeys: they could have rolled a moment before the probe took its pictures, or they may have tumbled down the hill many thousands of years ago.
The Moon and How to Observe It — PDF p. 48irregular motion in air that distorts or destabilizes an optical image
The airy pattern, an artifact introduced by optics, will distort according to the degree of atmospheric turbulence along its light path.
The Moon and How to Observe It — PDF p. 89On nights of poor visibility, it’s hardly worth observing the Moon with anything but the lowest powers, since turbulence in the Earth’s atmosphere will make the lunar surface appear to roll and shimmer, rendering any fine detail impossible to discern.
The Moon and How to Observe It — PDF p. 250unstable, irregular, and full of rapid changes
And even then, the efforts of the observer will amount to nothing if he or she is troubled by cloudy skies or turbulent atmospheric conditions.
Atlas of the Moon — PDF p. 93a state of violent disturbance or continuous disorder
There are no radial ray systems, mountain chains or chain craters on Io, as the surface is in constant turmoil.
The Moon and How to Observe It — PDF p. 77relating to electromagnetic radiation beyond the violet end of visible light
Alternatively, protons and ultraviolet radiation in the solar wind are capable of exciting the atoms in the vented gases, ionizing them to produce a glow discharge.
The Moon and How to Observe It — PDF p. 47Vitamin C helps protect the eyes against ultraviolet radiation and, being an antioxidant, it inhibits the natural oxidization of cells.
The Moon and How to Observe It — PDF p. 240the fully dark central part of a shadow
Since the Sun is an extended light source, some half a degree in diameter as seen from the Moon, the shadow is made up of two components – the umbra and the penumbra.
The Moon and How to Observe It — PDF p. 63The intensity of the darkness of the penumbra gradually rises from near zero at the penumbra’s outer edge to almost total shadow near the outer edge of the umbra.
The Moon and How to Observe It — PDF p. 63relating to the fully dark central region of a shadow
An umbral shadow cone over 1.3-million-km long is cast by the Earth.
The Moon and How to Observe It — PDF p. 64During a total lunar eclipse, the entire Moon enters the umbral shadow.
The Moon and How to Observe It — PDF p. 65lying beneath or forming the basis of something
Wrinkle ridges have a number of possible modes of formation, including mare contraction, topographic moulding to underlying features and vulcanism.
The Moon and How to Observe It — PDF p. 40However, it is possible that the arrangement of wrinkle ridges does not reflect the underlying topography, and that a buried crater does not really exist here.
The Moon and How to Observe It — PDF p. 166rising and falling in smooth, wave-like curves
Much of the planet is covered by an undulating landscape of low relief, a monotonous terrain accounting for around 90% of the surface.
The Moon and How to Observe It — PDF p. 71Rima Ariadaeus runs east across the undulating terrain between Agrippa and Julius Caesar to meet up with the border of Mare Tranquillitatis to the east.
The Moon and How to Observe It — PDF p. 138high or elevated land, especially above surrounding plains
Tycho is a large, prominent impact crater in the Moon’s southern uplands, 85 km across.
The Moon and How to Observe It — PDF p. 34Its flat lava-flooded floor, sunk about 1,000 m below the surrounding uplands, has a small lava-cut sinuous rille running down the middle.
The Moon and How to Observe It — PDF p. 41the upward movement or raising of rock or crust
Mascons were formed during the excavation of the nearside impact basins, when vast quantities of lunar crustal material were removed, leading to an immediate uplift of denser rocks from the Moon’s mantle.
The Moon and How to Observe It — PDF p. 23As the crust decompresses, rebound effects produce a central uplift in larger craters, and a substantial layer of melted rock accumulates within the crater’s bowl.
The Moon and How to Observe It — PDF p. 30a named valley in planetary nomenclature
Vallis Alpes, a large rift valley in the lunar Alps, was caused when crustal tension caused two parallel faults to appear across the mountains; the crust between the faults subsequently dropped down.
The Moon and How to Observe It — PDF p. 42a narrow raised or branching feature resembling a blood vessel
In many places the mare surfaces were folded into complex “wrinkle ridges” or “mare ridges” (called dorsum and dorsa), resembling protruding veins beneath the skin.
Atlas of the Moon — PDF p. 10speed in a specified direction
The Earth–Moon system has the largest amount of angular momentum (a product of the objects’ masses and velocities) in the Solar System; what mechanisms could possibly account for this?
The Moon and How to Observe It — PDF p. 12Since the Moon has no atmosphere to slow these objects as they plummet to the surface, the average impactor hits with an unimpeded interplanetary velocity of more than 70,000 km/hour.
The Moon and How to Observe It — PDF p. 29an opening through which gas, lava, or other material escapes
Low, rounded hills called “domes” – typically a few hundred meters high and with bases several kilometers across – are the remnants of ancient lunar volcanoes, and their tiny summit craterlets represent volcanic vents.
The Moon and How to Observe It — PDF p. 38Low-viscosity lava, squeezed through very narrow volcanic vents, can produce fire fountains that spray a multitude of tiny droplets – successive eruptions are capable of building up quite steep-sided volcanic cones.
The Moon and How to Observe It — PDF p. 38able to perform many different functions or adapt to varied uses
Digital camcorders are the lightest and most versatile camcorders, and their images can be easily transferred to a computer for digital editing, employing the same techniques used with images obtained with a webcam (see below).
The Moon and How to Observe It — PDF p. 101A telescope that allows the eyepieces to be interchanged, allowing the magnification to be alternated between low and high powers, will be a somewhat more versatile instrument.
The Moon and How to Observe It — PDF p. 247to move rapidly back and forth
In some basic SLRs, the movement of the shutter can vibrate the camera and telescope, causing a little blurring of the image; this would, of course, present more of a problem when taking high-magnification lunar images, as the effects of any movement of the telescope would be exacerbated.
The Moon and How to Observe It — PDF p. 95rapid repeated movement back and forth
To minimize the effects of vibration that occurs when the shutter button is pressed, a cable release can be used.
The Moon and How to Observe It — PDF p. 95Vibration or a slight, sudden knock to the tube can cause misalignment of the primary mirror in its cell or the secondary in its spider.
The Moon and How to Observe It — PDF p. 248the surrounding area or nearby region
However, the theory does not explain the identical oxygen isotopes in Earth and Moon rocks, which imply that the Earth and Moon were formed in the same vicinity of the early Solar System.
The Moon and How to Observe It — PDF p. 17During totality, the brighter stars and planets become easily visible, even those that lie in the vicinity of the Sun.
The Moon and How to Observe It — PDF p. 65having a blue-purple color at the short-wavelength end of visible light
Many budget imported achromatic refractors have focal lengths of f/8 to as short as f/5, and although they do display noticeable chromatic distortion, mainly in the form of a violet fringe around the Moon and the brighter planets, they offer good resolution and good contrast.
The Moon and How to Observe It — PDF p. 247a fluid's resistance to flowing
Basaltic in composition, the marial lava flows had the viscosity of motor oil and were ductile and fast-moving.
The Moon and How to Observe It — PDF p. 20Most domes are volcanic features built up by successive eruptions of lava that may have had a viscosity equivalent to that which formed (and is still forming) the Hawaiian shield volcanoes on Earth.
The Moon and How to Observe It — PDF p. 118glasslike or relating to the clear gel inside the eye
Floaters are the shadows cast onto the retina by the remnants of dead cells floating in the vitreous humor.
The Moon and How to Observe It — PDF p. 240This lens focuses light across a chamber filled with vitreous humor, a clear jelly that gives the eyeball its rigidity, and an upside-down image is projected onto the retina inside the back part of the eyeball.
The Moon and How to Observe It — PDF p. 239a substance that vaporizes easily, or readily able to vaporize
Taken as a whole, the Moon possesses substantially less iron than the Earth; its rocks contain no water and they are depleted in other volatiles (substances that vaporize at relatively low temperatures).
The Moon and How to Observe It — PDF p. 12The cometary nuclei impacting on the Moon’s surface would have been instantly vaporized, but the volatiles would have quickly solidified into a vast cloud of snowflakes if the impact had taken place on the cold, unilluminated hemisphere.
The Moon and How to Observe It — PDF p. 43volcanic activity and the processes that produce it
The unique chemical makeup of KREEP enables it to be used as a chemical tracer to chart the convoluted history of lunar volcanism and asteroidal bombardment.
The Moon and How to Observe It — PDF p. 19KREEP represents the last vestiges of the Moon’s hot magma ocean, and was distributed around the Moon’s surface by volcanism and impact.
The Moon and How to Observe It — PDF p. 20the processes by which magma and volcanic material reach or affect a surface
Beginning with the Eratosthenes impact around 3.2 billion years ago, the Eratosthenian Period saw the dwindling of large-scale lunar vulcanism and a coincidental steep decline in the rates of major impacts.
The Moon and How to Observe It — PDF p. 21Wrinkle ridges have a number of possible modes of formation, including mare contraction, topographic moulding to underlying features and vulcanism.
The Moon and How to Observe It — PDF p. 40a digital video camera that sends images directly to a computer
For example, afocal digicam imaging requires different techniques from those used imaging the Moon with a webcam and Barlow lens at prime focus.
The Moon and How to Observe It — PDF p. 99Any commercial webcam hooked up to a computer and a telescope can be used to image the Moon and the brighter planets.
The Moon and How to Observe It — PDF p. 101a piece or area that is thick or broad at one end and tapers at the other
The far-northwestern border is marked by Montes Caucasus (Caucasus Mountains), an impressive range that makes a north–south wedge more than 500 km long, separating eastern Mare Imbrium and northwestern Mare Serenitatis.
The Moon and How to Observe It — PDF p. 134An imposing crater, Bürg (40 km), lies just off-center in Lacus Mortis, and this sits upon a triangular wedge of higher ground that may be Lacus Mortis’ original central uplift.
The Moon and How to Observe It — PDF p. 144thin, narrow, and stiff or wirelike
Between Nielsen and Lichtenberg (20 km), running south of Naumann (9.6 km), can be found the wiry wrinkle ridges Dorsum Scilla (120 km long) and Dorsa Whiston (120 km long).
The Moon and How to Observe It — PDF p. 178Brenner (97 km) is highly eroded and lies at the southern end of a prominent wiry ridge that runs from the southeast of Piccolomini, its shadow visible under a low morning illumination.
The Moon and How to Observe It — PDF p. 229to move or extend through a series of sharp alternating turns
The floor of the valley is flat, and a very narrow sinuous rille, which is not visible from the Earth, zigzags along it.
Atlas of the Moon — PDF p. 102the chemical element with atomic number 30
Finally, zinc helps maintain a healthy retina and can play a part in preventing AMD.
The Moon and How to Observe It — PDF p. 240variable optical magnification, or the act of changing it
If the digicam has a zoom, the lunar terminator can be magnified, aiding focusing further.
The Moon and How to Observe It — PDF p. 100Using the digicam’s zoom facility (if it has one) can eliminate the problems of image vignetting that tend to plague afocal photographs.
The Moon and How to Observe It — PDF p. 100869 shortlisted items were reviewed across eight packets. 177 were removed during final review. The published entries include one or two complete source sentences according to what the books reliably provide; a third sentence is used only when it demonstrates a distinct sense or collocation.