Observing the Moon - AbsoluteAstronomy.com

The Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

is Earth

Earth

Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

's largest natural satellite

Natural satellite

A natural satellite or moon is a celestial body that orbits a planet or smaller body, which is called its primary. The two terms are used synonymously for non-artificial satellites of planets, of dwarf planets, and of minor planets....

and the nearest major celestial object. Observing the Moon can be accomplished by using a variety of instruments ranging from the naked eye to large telescope

Telescope

A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...

s. For most people, the Moon is the only celestial object upon which surface features can be discerned with the naked eye

Naked eye

The naked eye is a figure of speech referring to human visual perception unaided by a magnifying or light-collecting optical device, such as a telescope or microscope. Vision corrected to normal acuity using corrective lenses is considered "naked"...

(some people with good eyesight can see large sunspots on the surface of the Sun using handheld solar filters).

Optimal viewing times

Contrary to popular belief, the Moon should ideally not be viewed at its full phase

Lunar phase

A lunar phase or phase of the moon is the appearance of the illuminated portion of the Moon as seen by an observer, usually on Earth. The lunar phases change cyclically as the Moon orbits the Earth, according to the changing relative positions of the Earth, Moon, and Sun...

. During a full moon, rays of sunlight are hitting the visible portion of the moon perpendicular

Perpendicular

In geometry, two lines or planes are considered perpendicular to each other if they form congruent adjacent angles . The term may be used as a noun or adjective...

to the surface. As a result there is much less surface detail visible during a full moon than during other phases (such as the quarter and crescent phases) when sunlight hits the Moon at a much shallower angle. In addition, the brightness of a full moon as compared to a phase where a smaller percentage of the surface is illuminated tends to wash out substantial amounts of detail and can actually leave an afterimage

Afterimage

An afterimage or ghost image or image burn-in is an optical illusion that refers to an image continuing to appear in one's vision after the exposure to the original image has ceased...

on an observer's eye that can persist for several minutes. First quarter (six to nine days past new moon

New moon

In astronomical terminology, the new moon is the lunar phase that occurs when the Moon, in its monthly orbital motion around Earth, lies between Earth and the Sun, and is therefore in conjunction with the Sun as seen from Earth...

) is generally considered the best time to observe the Moon for backyard stargazers. It is true that if one views the Moon during this time, a smaller percentage of the surface will be seen at a time, however the detail will be vastly more impressive. Shadow

Shadow

A shadow is an area where direct light from a light source cannot reach due to obstruction by an object. It occupies all of the space behind an opaque object with light in front of it. The cross section of a shadow is a two-dimensional silhouette, or reverse projection of the object blocking the...

s and detail are most pronounced along the "terminator

Terminator (solar)

A terminator, twilight zone or "grey line" is a moving line that separates the illuminated day side and the dark night side of a planetary body...

", the dividing line between the illuminated (day side) and dark (night side) of the Moon.

Naked eye

Generally, the Moon can be viewed even with the naked eye, however it may be more enjoyable with optical instruments. The primary lunar surface features detectable to the naked eye are the lunar maria or "seas", large basalt

Basalt

Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...

ic plains which form the familiar "Man in the Moon

Man in the Moon

The Man in the Moon is an imaginary figure resembling a human face, head or body, that observers from some cultural backgrounds typically perceive in the bright disc of the full moon...

" and other figures seen by many people who take a glance at a full moon

Full moon

Full moon lunar phase that occurs when the Moon is on the opposite side of the Earth from the Sun. More precisely, a full moon occurs when the geocentric apparent longitudes of the Sun and Moon differ by 180 degrees; the Moon is then in opposition with the Sun.Lunar eclipses can only occur at...

. The maria cover about 35% of the surface. The contrast between the less reflective dark gray maria and the more reflective gray/white lunar highlands is easily visible without optical aid. Under good viewing conditions, those with keen eyesight may also be able to see some of the following features:

Bright region around Copernicus
Copernicus (lunar crater)
Copernicus is a prominent lunar impact crater named after the astronomer Nicolaus Copernicus, located in eastern Oceanus Procellarum. It is estimated to be about 800 million years old, and typifies craters that formed during the Copernican period in that it has a prominent ray system.-...
Mare Nectaris
Mare Nectaris
The Sea of Nectar is a small lunar mare or sea located between the Sea of Tranquillity and the Sea of Fecundity . Montes Pyrenaeus borders the mare to the west and the large crater near the south center of the mare is known as Rosse...
Mare Humorum
Mare Humorum
Mare Humorum is a lunar mare. The impact basin it is located in is 825 kilometers across. It was not sampled by the Apollo program, so a precise age has not been determined. However, geological mapping indicates that it is intermediate in age between the Imbrium and Nectaris Basins, suggesting an...
Bright region around Kepler
Kepler (lunar crater)
Kepler is a lunar impact crater that lies between the Oceanus Procellarum to the west and Mare Insularum in the east. To the southeast is the crater Encke....
Gassendi
Gassendi (crater)
Gassendi is a large lunar crater feature located at the northern edge of Mare Humorum. The formation has been inundated by lava during the formation of the mare, so only the rim and the multiple central peaks remain above the surface. The outer rim is worn and eroded, although it retains a...

region
Plinius
Plinius (crater)
Plinius is a prominent lunar impact crater on the border between Mare Serenitatis to the north and Mare Tranquilitatis to the south. South-southeast of Plinius is the crater Ross, and to the northeast is Dawes. Just to the north is a system of rilles named the Rimae Plinius...

region
Mare Vaporum
Mare Vaporum
Mare Vaporum is a lunar mare located between the southwest rim of Mare Serenitatis and the southeast rim of Mare Imbrium. The lunar material surrounding the mare is from the Lower Imbrian epoch, and the mare material is from the Eratosthenian epoch. The mare lies in an old basin or crater that is...
Lubiniesky
Lubiniezky (crater)
Lubiniezky is a lava-flooded lunar crater on the northwest edge of Mare Nubium. This feature is most readily located by finding the prominent crater Bullialdus to the southeast....

region
Sinus Medii
Sinus Medii
Sinus Medii is a small lunar mare that is located at the intersection of the Moon's equator and prime meridian. As seen from the Earth, this feature is located in the central part of the Moon's near side, and it is the point closest to the Earth...
Faintly shaded area near Sacrobosco
Sacrobosco (crater)
Sacrobosco is an irregular lunar impact crater that is located in the rugged southern highlands to the west of the Rupes Altai escarpment. It is a readily identified feature due to the three circular craters that lie on its floor. The rim of Sacrobosco is heavily worn and eroded, especially in the...
Dark spot at foot of Mons Huygens
Riphean Mountains

Another interesting phenomenon visible with the naked eye is Earthshine. Best visible shortly before or after new moon (during the waning and waxing crescent phases respectively), Earthshine is the faint glow of the non-illuminated (night) side of the Moon caused by sunlight reflecting off the surface of Earth (which would appear nearly full to an observer situated on the Moon at this time) and onto the night side of the Moon. By the time the Moon reaches first quarter however, the sunlight illuminated portion of the Moon becomes far too bright for Earthshine to be seen with the naked eye however it can still be observed telescopically.

Binoculars

Binoculars are commonly used by those just beginning to observe the Moon and many experienced amateur astronomer

Amateur astronomy

Amateur astronomy, also called backyard astronomy and stargazing, is a hobby whose participants enjoy watching the night sky , and the plethora of objects found in it, mainly with portable telescopes and binoculars...

s prefer the view in binoculars to a telescopic view due to the larger field of view

Field of view

The field of view is the extent of the observable world that is seen at any given moment....

. Their high level of portability makes them the simplest device used to see more detail on the surface beyond naked eye observing.

The primary disadvantage of binoculars is that they cannot be held very steady unless one utilizes a commercial or homemade binocular tripod. The recent introduction of image-stabilized binoculars

Image-stabilized binoculars

Image-stabilized binoculars are binoculars that have a mechanism for decreasing the apparent motion of the view due to binocular movement.Image stabilized binoculars are designed to minimize image shaking in hand-held binoculars. Higher power binoculars bring the image closer, but the image shift...

has changed this to some extent; however, cost is still an issue.

Telescopes

To some it may be far more desirable to utilize a telescope in which case far more options for observing the Moon exist. Even a small, well-made telescope will show the observer far more than is visible with the naked eye or small binoculars. As the aperture

Aperture

In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture of an optical system is the opening that determines the cone angle of a bundle of rays that come to a focus in the image plane. The aperture determines how collimated the admitted rays are,...

of the telescope mirror (in the case of a reflecting telescope

Reflecting telescope

A reflecting telescope is an optical telescope which uses a single or combination of curved mirrors that reflect light and form an image. The reflecting telescope was invented in the 17th century as an alternative to the refracting telescope which, at that time, was a design that suffered from...

) or lens (in the case of a refracting telescope

Refracting telescope

A refracting or refractor telescope is a type of optical telescope that uses a lens as its objective to form an image . The refracting telescope design was originally used in spy glasses and astronomical telescopes but is also used for long focus camera lenses...

) increases, smaller and smaller features will begin to appear. With large amateur telescopes, features as small as 0.6 miles (1 km) in diameter can be observed depending on atmospheric conditions.

Most astronomers use different kinds of filters in order to bring out the contrast of certain surface features. Simple neutral density filter

Neutral density filter

In photography and optics, a neutral density filter or ND filter can be a colorless or grey filter. An ideal neutral density filter reduces and/or modifies intensity of all wavelengths or colors of light equally, giving no changes in hue of color rendition.The purpose of standard photographic...

s are also common as they can cut down the amount of light reaching the eye by 60–95%, something that is helpful especially when observing a full or gibbous moon so the surface does not appear as washed out.

Lunar occultations

An occultation

Occultation

An occultation is an event that occurs when one object is hidden by another object that passes between it and the observer. The word is used in astronomy . It can also refer to any situation wherein an object in the foreground blocks from view an object in the background...

is an astronomical event where a celestial object appears completely hidden by another, closer body (with a greater angular diameter

Angular diameter

The angular diameter or apparent size of an object as seen from a given position is the “visual diameter” of the object measured as an angle. In the vision sciences it is called the visual angle. The visual diameter is the diameter of the perspective projection of the object on a plane through its...

) due to the passage of the closer object directly between the more distant object and the observer. Due to the large apparent size of the Moon, lunar occultations are quite common and when a bright celestial object is involved, the result is an event that can be easily observed using the naked eye. The Moon almost constantly occults faint stars as it orbits the Earth but because even a young Moon appears immensely brighter than these stars, these events are difficult to observe using amateur telescopes. However, the Moon does frequently occult brighter stars and even planets due to its close proximity to the ecliptic

Ecliptic

The ecliptic is the plane of the earth's orbit around the sun. In more accurate terms, it is the intersection of the celestial sphere with the ecliptic plane, which is the geometric plane containing the mean orbit of the Earth around the Sun...

.
Four first magnitude

Apparent magnitude

The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...

stars, Regulus

Regulus

Regulus is the brightest star in the constellation Leo and one of the brightest stars in the night sky, lying approximately 77.5 light years from Earth. Regulus is a multiple star system composed of four stars which are organized into two pairs...

, Spica

Spica

Spica is the brightest star in the constellation Virgo, and the 15th brightest star in the nighttime sky. It is 260 light years distant from Earth...

, Antares

Antares

Antares is a red supergiant star in the Milky Way galaxy and the sixteenth brightest star in the nighttime sky . Along with Aldebaran, Spica, and Regulus it is one of the four brightest stars near the ecliptic...

, and Aldebaran

Aldebaran

Aldebaran is a red giant star located about 65 light years away in the zodiac constellation of Taurus. With an average apparent magnitude of 0.87 it is the brightest star in the constellation and is one of the brightest stars in the nighttime sky...

, are sufficiently close to the ecliptic that they may be occulted by the Moon. In addition, two star cluster

Star cluster

Star clusters or star clouds are groups of stars. Two types of star clusters can be distinguished: globular clusters are tight groups of hundreds of thousands of very old stars which are gravitationally bound, while open clusters, more loosely clustered groups of stars, generally contain less than...

s visible to the naked eye, the Beehive Cluster

Beehive Cluster

The Beehive Cluster, also known as Praesepe , M44, NGC 2632, or Cr 189, is an open cluster in the constellation Cancer. It is one of the nearest open clusters to the Solar System, and it contains a larger star population than most other nearby clusters...

and the Pleiades

Pleiades (star cluster)

In astronomy, the Pleiades, or Seven Sisters , is an open star cluster containing middle-aged hot B-type stars located in the constellation of Taurus. It is among the nearest star clusters to Earth and is the cluster most obvious to the naked eye in the night sky...

, are often occulted. Depending on one's location on the Earth, there are usually several occultations involving naked eye objects every year and many more that can be observed using binoculars or a telescope.

Accurate timings (accuracy within a few tenths of a second) of lunar occultations are scientifically useful in fields such as lunar topography, astrometry

Astrometry

Astrometry is the branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies. The information obtained by astrometric measurements provides information on the kinematics and physical origin of our Solar System and our Galaxy, the Milky...

, and binary star

Binary star

A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...

studies. These timings are regularly obtained by amateur astronomers using readily available instruments to observe the Moon.

Transient Lunar Phenomena

A transient lunar phenomenon (TLP) or "Lunar Transient Phenomena" (LTP), refers to short-lived lights, colors, or changes in appearance of the lunar surface.

Claims of these phenomena go back at least 1,000 years, with some having been observed independently by multiple witnesses or reputable scientists. Nevertheless, the majority of transient lunar phenomena reports are irreproducible and do not possess adequate control experiments that could be used to distinguish among alternative hypotheses. Few reports concerning these phenomena are ever published in peer reviewed scientific journals, and rightfully or wrongfully, the lunar scientific community rarely discusses these observations.

Most lunar scientists will acknowledge that transient events such as outgassing

Outgassing

Outgassing is the release of a gas that was dissolved, trapped, frozen or absorbed in some material. As an example, research has shown how the concentration of carbon dioxide in the Earth's atmosphere has sometimes been linked to ocean outgassing...

and impact cratering do occur over geologic time: the controversy lies in the frequency of such events.

A number of astronomical societies around the world have implemented their own TLP watch programs and TLP alert networks.

Features with reported TLP Associations

Agrippa (crater)

Agrippa is a lunar impact crater that is located at the southeast edge of the Mare Vaporum. It is located to the north of the crater Godin, and the irregular Tempel lies just to the east. To the north and northeast, the rille designated Rima Ariadaeus follows a course to the east-southeast,...

Alphonsus (crater)

Alphonsus is an ancient impact crater on the Moon that dates from the immediate post-Nectarian era. It is located on the lunar highlands on the eastern end of Mare Nubium, west of the Imbrian Highlands, and slightly overlaps the crater Ptolemaeus to the north. The surface is broken and irregular...

Archimedes (crater)

Archimedes is a large lunar impact crater on the eastern edges of the Mare Imbrium. To the south of the crater extends the Montes Archimedes mountainous region. On the southeastern rim is the Palus Putredinis flooded plain, containing a system of rilles named the Rimae Archimedes that extend over...

Aristarchus (crater)

Aristarchus is a prominent lunar impact crater that lies in the northwest part of the Moon's near side. It is considered the brightest of the large formations on the lunar surface, with an albedo nearly double that of most lunar features. The feature is bright enough to be visible to the naked eye,...

Aristoteles (crater)

Aristoteles is a lunar impact crater that lies near the southern edge of the Mare Frigoris and to the east of the Montes Alpes mountain range. To the south of Aristoteles lies the slightly smaller crater Eudoxus and these two form a distinctive pair for a telescope observer. An arc of mountains...

Atlas (crater)

Atlas is a prominent lunar impact crater that is located in the northeast part of the Moon, to the southeast of Mare Frigoris. Just to the west is the slightly smaller but still prominent crater Hercules. Northeast of Atlas is the large Endymion....

Alphonsus (crater)

Bullialdus (crater)

Bullialdus is a lunar impact crater located in the western part of the Mare Nubium. To the north by north-west is the broken-rimmed and lava-flooded crater Lubiniezky. South-west of Bullialdus lies the smaller crater König....

Calippus (crater)

Calippus is a small lunar crater that is located on the eastern edge of the rugged Montes Caucasus mountain range in the northern part of the Moon...

Cassini (crater)

Cassini (lunar crater)

Cassini is a lunar impact crater that is located in the Palus Nebularum, at the eastern end of Mare Imbrium. To the northeast is the Promontorium Agassiz, the southern tip of the Montes Alpes mountain range. South by south-east of Cassini is the crater Theaetetus. To the northwest is the lone peak...

Censorinus (crater)

Censorinus is a tiny lunar impact crater located on a rise to the southeast of the Mare Tranquillitatis. To the northeast is the crater Maskelyne....

Clavius (crater)

Clavius is one of the largest crater formations on the Moon, and it is the third largest crater on the visible near side. It is located in the rugged southern highlands of the Moon, to the south of the prominent ray crater Tycho.- Description :...

Cleomedes (crater)

Cleomedes is a prominent lunar crater located in the northeast part of the visible Moon, to the north of Mare Crisium. It is surrounded by rough ground with multiple crater impacts. The irregular crater Tralles intrudes into the northwest rim. To the east is Delmotte...

Copernicus (crater)

Copernicus (lunar crater)

Copernicus is a prominent lunar impact crater named after the astronomer Nicolaus Copernicus, located in eastern Oceanus Procellarum. It is estimated to be about 800 million years old, and typifies craters that formed during the Copernican period in that it has a prominent ray system.-...

Eratosthenes (crater)

Eratosthenes is a relatively deep lunar impact crater that lies on the boundary between the Mare Imbrium and Sinus Aestuum mare regions. It forms the western terminus of the Montes Apenninus mountain range. The crater has a well-defined circular rim, terraced inner wall, central mountain peaks, an...

Fracastorius (crater)

Fracastorius is the lava-flooded remnant of an ancient lunar impact crater located at the southern edge of Mare Nectaris. To the northwest of this formation lies the crater Beaumont, while to the northeast is Rosse....

Gassendi (crater)

Gassendi is a large lunar crater feature located at the northern edge of Mare Humorum. The formation has been inundated by lava during the formation of the mare, so only the rim and the multiple central peaks remain above the surface. The outer rim is worn and eroded, although it retains a...

Grimaldi (crater)

Grimaldi is a large basin located near the western limb of the Moon. It lies to the southwest of the Oceanus Procellarum, and southeast of the crater Riccioli...

Herodotus (crater)

Herodotus is a lunar crater located on a low shelf in the midst of the Oceanus Procellarum. To the east is the slightly larger crater Aristarchus. West across the mare is Schiaparelli. Almost due south on the mare surface is a solitary lunar dome designated Herodotus Omega .The crater Herodotus has...

Sinus Iridum

Sinus Iridum is a plain of basaltic lava that forms a northwestern extension to the Mare Imbrium. It is surrounded from the northeast to the southwest by the Montes Jura range. The protruding part of the range at the southwest end is named Promontorium Heraclides, while that at the northeast end...

Kepler (crater)

Kepler (lunar crater)

Kepler is a lunar impact crater that lies between the Oceanus Procellarum to the west and Mare Insularum in the east. To the southeast is the crater Encke....

Lambert (lunar crater)

Lambert is a lunar impact crater on the southern half of the Mare Imbrium basin. It lies to the east and somewhat south of the slightly larger crater Timocharis. To the south is the smaller Pytheas, and some distance to the west-southwest is Euler....

Linné (crater)

Linné is a small lunar impact crater located in the western Mare Serenitatis. The mare around this feature is virtually devoid of other features of interest. The nearest named crater is Banting to the east-southeast....

Manilius (crater)

Manilius is a lunar impact crater on the northeast edge of Mare Vaporum. It has a well-defined rim with a sloping inner surface that runs directly down to the ring-shaped mound of scree along the base, and a small outer rampart. The small crater interior has a higher albedo than the surroundings,...

Mare Crisium

Mare Crisium is a lunar mare located in the Moon's Crisium basin, just northeast of Mare Tranquillitatis. This basin is of the Pre-Imbrian period, 4.55 to 3.85 billion years ago. This mare is in diameter, and 176,000 km2 in area. It has a very flat floor, with a ring of wrinkled ridges...

Menelaus (crater)

Menelaus is a young lunar impact crater located on the southern shore of Mare Serenitatis near the eastern end of the Montes Hæmus mountain range. The crater was named after the jilted king of Sparta from the Iliad. To the southwest is the small crater Auwers, and to the southwest is the even...

Mons Piton

Mons Piton is an isolated lunar mountain that is located in the eastern part of the Mare Imbrium, to the north-northwest of the crater Aristillus. Due east of Mons Piton is the flooded crater Cassini, and to the west-northwest lies Piazzi Smyth...

Mons Pico

Mons Pico is a solitary lunar mountain that lies in the northern part of the Mare Imbrium basin, and to the south of the dark-floored crater Plato. This peak forms part of the surviving inner ring of the Imbrium basin. This ring continues to the northwest and with the Montes Teneriffe and Montes...

Picard (crater)

Picard is a lunar impact crater that lies in Mare Crisium. To the west is the almost completely flooded crater Yerkes. Due east of Picard is the tiny Curtis. being slightly larger than Peirce to the north-northwest...

Plato (crater)

Plato is the lava-filled remains of a lunar impact crater on the moon. It is located on the northeastern shore of the Mare Imbrium, at the western extremity of the Montes Alpes mountain range. In the mare to the south are several rises collectively named the Montes Teneriffe. To the north lies the...

Posidonius (crater)

Posidonius is a lunar impact crater that is located on the western edge of Mare Serenitatis, to the south of Lacus Somniorum. The crater Chacornac is attached to the southeast rim, and to the north is Daniell....

Proclus (crater)

Proclus is a young lunar impact crater located to the west of the Mare Crisium, on the east shore of the Palus Somni. It lies to the south of the prominent, terraced crater Macrobius, and west-northwest of the lava-flooded Yerkes...

Promontorium Laplace

Promontorium Laplace is a raised mountainous cape situated at the end of Montes Jura in Mare Imbrium on the near side of the Moon. Its selenographic coordinates are 46.0° N, 26.0° W and it is 2600 meters high. It is the east beginning of the bay of Sinus Iridum....

Riccioli (crater)

Riccioli is a large lunar impact crater located near the western limb of the Moon. It lies just to the northwest of the even larger and more prominent crater Grimaldi. To the southwest are the craters Hartwig and Schlüter that lie on the northeastern edge of Montes Cordillera, the ring-shaped range...

Schickard (crater)

Schickard is a lunar impact crater of the form called a walled plain. It lies in the southwest sector of the Moon, near the lunar limb. As a result the crater appears oblong due to foreshortening. Attached to the northern rim is the lesser crater Lehmann, and to the northeast is the even smaller...

Taruntius (crater)

Taruntius is a lunar crater on the northwestern edge of Mare Fecunditatis. To the northwest is the lava-flooded crater Lawrence, and to the north lie the craters Watts and da Vinci...

Theophilus (crater)

Theophilus is a prominent lunar impact crater that lies between Sinus Asperitatis in the north and Mare Nectaris to the southeast. It partially intrudes into the comparably sized crater Cyrillus to the southwest. To the east is the smaller crater Mädler and further to the south-southeast is Beaumont...

Timocharis (crater)

Timocharis is a prominent lunar impact crater located on the Mare Imbrium. The closest crater of comparable dimensions is Lambert to the west. The smaller craters Feuillée and Beer lie to the east of Timocharis....

Tycho (crater)

Tycho is a prominent lunar impact crater located in the southern lunar highlands, named after the Danish astronomer Tycho Brahe . To the south is the crater Street; to the east is Pictet, and to the north-northeast is Sasserides. The surface around Tycho is replete with craters of various sizes,...

Vallis Schröteri

Schroter's Valley, frequently known by the Latinized name Vallis Schröteri, is a sinuous valley or rille on the surface of the near side of the Moon. It is located on a rise of continental ground, sometimes called the Aristarchus plateau, that is surrounded by the Oceanus Procellarum to the south...

Zagut (crater)

Zagut is a crater located in the heavily impacted southeast sector of the Moon. It is almost surrounded by other named craters, with Wilkins to the northwest, Lindenau to the east, Rabbi Levi in the southeast, and Celsius to the southwest....

Blinking devices

A number of observers employ different coloured filters

Filter (optics)

Optical filters are devices which selectively transmit light of different wavelengths, usually implemented as plane glass or plastic devices in the optical path which are either dyed in the mass or have interference coatings....

to determine coloured transient events on the Moon. By quickly alternating filters of opposing colours in the telescopic light path, faintly coloured areas on the Moon can stand out more by appearing to flicker on and off. A red area will appear brighter when viewed through a red filter and darker when seen through a blue filter. It is possible to alternate the filters manually however, this requires a certain dexterity of the hand and good coordination. A purpose built filter wheel is much more viable alternative, and this can be motorised, so the observer can devote all of their concentration to what is going on through the eyepiece. There are, however a number of features on the Moon that will appear to blink naturally, among the being the southwestern part of Fracastorius (crater)

Fracastorius (crater)

, and a section of the wastern wall of Plato (crater)

Plato (crater)

. A special filter wheel called a "crater extinction device" is capable of measuring the brightness of an individual lunar feature to be measured according to the point where it ceases to be visible.

Other items of interest

Because the Moon is so bright, it is especially interesting to see objects "superimposed" on it. One particular point of interest is an ISS (International Space Station

International Space Station

The International Space Station is a habitable, artificial satellite in low Earth orbit. The ISS follows the Salyut, Almaz, Cosmos, Skylab, and Mir space stations, as the 11th space station launched, not including the Genesis I and II prototypes...

) transit. These can be seen every so often and several services exist that will contact you with expected times of transit.

Optimal viewing times

Naked eye

Binoculars

Telescopes

Lunar occultations

Transient Lunar Phenomena

Features with reported TLP Associations

Blinking devices

Other items of interest

See also