Selenographic coordinates are used to refer to locations on the surface of Earth's moon. Any position on the lunar surface can be referenced by specifying two numerical values, which are comparable to the latitude and longitude of Earth. The longitude gives the position east or west of the Moon's prime meridian, which is the line of longitude passing through the point on the lunar surface directly facing Earth. (See also Earth's prime meridian.) This can be thought of as the mid-point of the visible Moon as seen from the Earth. The latitude gives the position north or south of the lunar equator. Both of these coordinates are given in terms of degrees. Jump to: navigation, search Earth, also known as the Earth, Terra, and (mostly in the 19th century) Tellus, is the third-closest planet to the Sun. ... Jump to: navigation, search Crust composition Oxygen 43% Silicon 21% Aluminium 10% Calcium 9% Iron 9% Magnesium 5% Titanium 2% Nickel 0. ... Jump to: navigation, search Latitude, sometimes denoted by the Greek letter φ, gives the location of a place on Earth north or south of the Equator. ... Jump to: navigation, search Map of Earth showing lines of longitude, which appear curved and vertical in this projection, but are actually halves of great circles Longitude, sometimes denoted by the Greek letter λ, describes the location of a place on Earth east or west of a north-south line called... The Prime Meridian, Greenwich The Prime Meridian is the meridian (line of longitude) passing through the Royal Greenwich Observatory, Greenwich, England; it is the meridian at which longitude is 0 degrees. ... Jump to: navigation, search The equator is an imaginary circle drawn around a planet (or other astronomical object) at a distance halfway between the poles. ... A degree (in full, a degree of arc), usually symbolized °, is a measurement of plane angle, representing 1／360 of a full rotation. ...

Astronomers defined the fundamental location in the selenographic coordinate system by the small, bowl-shaped satellite crater 'Mösting A'. The coordinates of this crater are defined as:

Latitude:	3° 12' 43.2"
Longitude:	5° 12' 39.6"

The coordinate system has become precisely defined due to the Lunar Laser Ranging Experiment. Categories: Physics stubs | Measuring instruments | Astronomy | General relativity | Apollo program ...

Selenographic colongitude

The selenographic colongitude is the longitude of the morning terminator on the Moon, as measured in degrees westward from the prime meridian. The morning terminator forms a half-circle across the Moon where the Sun is just starting to rise. As the Moon continues in its orbit, this line advances in longitude. The value of the selenographic colongitude increases from 0° to 359° in the direction of the advancing terminator. A composite image showing the terminator crossing Europe and Africa The terminator is the line between the illuminated, day side and dark, night side of a planetary body (also known as the grey line). It is defined as the locus of points on a moon or planet where the line...

Sunrise occurs at the prime meridian when the Moon reaches First Quarter, after one fourth of a lunar day. At this location the selenographic colongitude at sunrise is defined as 0°. Thus, by the time of the Full Moon the colongitude increases to 90°; at Last Quarter it is 180°, and at the New Moon the colongitude reaches 270°. Note that the Moon is invisible from the Earth at New Moon phase except during a solar eclipse. See also Day (language) A day (symbol: d) is a unit of time. ... The Galileo spacecraft took this composite image on 7 December 1992 on its way to explore the Jupiter system in 1995-97. ... Traditionally, the lunar phase new moon begins with the first visible crescent of the Moon, after conjunction with the Sun. ... Jump to: navigation, search This article needs to be cleaned up to conform to a higher standard of quality. ...

The low angle of incidence of arriving sunlight tends to pick out features by the sharp shadows they cast, thus the area near the terminator is usually the most favorable for viewing or photographing lunar features through a telescope. The observer will need to know the location of the terminator to plan observations of selected features. The selenographic colongitude is useful for this purpose. An angle of incidence is the angle between a beam incident on a surface and the normal (line perpendicular to the surface at the point of incidence). ... A photograph (often just called a photo) is an image (or a representation of that on e. ... Jump to: navigation, search 50 cm refracting telescope at Nice Observatory. ...

The selenographic longitude of the evening terminator is equal to the colongitude plus 180°.

References

• "A Unified Lunar Control Network — The Near Side", Merton E. Davies, Tim R. Colvin, & Donald L. Mayer, RAND Corporation, Santa Monica, 1987.