ELONGATION

in astronomy, the angular distance in celestial longitude separating the Moon or a planet from the Sun. The greatest elongation possible for the two inferior planets (those closer than the Earth to the Sun) is about 48 in the case of Venus and about 28 in that of Mercury. Elongation may also refer to the angular distance of any celestial body from another around which it revolves or from a particular point in the sky; e.g., the extreme east or west position of a star with reference to the north celestial pole.