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In contrast, the Lunar distance (LD or ), or Earth–Moon characteristic distance, is a unit of measure in astronomy. More technically, it is the semi-major axis of the geocentric lunar orbit . The lunar distance is on average approximately 385,000 km (239,000 mi), or 1.28 light-seconds ; this is roughly 30 times Earth's diameter or 9.5 times ...
In celestial navigation, lunar distance, also called a lunar, is the angular distance between the Moon and another celestial body. The lunar distances method uses this angle and a nautical almanac to calculate Greenwich time if so desired, or by extension any other time. That calculated time can be used in solving a spherical triangle.
Chart of the far side of the moon with lines of longitude and latitude. The selenographic coordinate system is 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 lunar orbit's major axis – the longest diameter of the orbit, joining its nearest and farthest points, the perigee and apogee, respectively – makes one complete revolution every 8.85 Earth years, or 3,232.6054 days, as it rotates slowly in the same direction as the Moon itself (direct motion) – meaning precesses eastward by 360°.
The Stonyhurst heliographic coordinate system, developed at Stonyhurst College in the 1800s, has its origin (where longitude and latitude are both 0°) at the point where the solar equator intersects the central solar meridian as seen from Earth. Longitude in this system is therefore fixed for observers on Earth. [8] [5]
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Its most extensive topographic feature is the giant far-side South Pole–Aitken basin, some 2,240 km (1,390 mi) in diameter, the largest crater on the Moon and the second-largest confirmed impact crater in the Solar System. [117] [118] At 13 km (8.1 mi) deep, its floor is the lowest point on the surface of the Moon.