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elongation



  1. elongation
    The geocentric angle between a planet and the Sun, measured in the plane of the planet, Earth, and Sun. Planetary elongations range from 0 to 180, east or west of the Sun. Greatest elongation is the instant at which the geocentric angular distance of Mercury or Venus from the Sun is a maximum.

  2. The angle between a planet and one of its satellites as seen from Earth, measured from 0° east or west of the planet, in the plane of the planet, satellite, and Earth.

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   • CELESTIAL MECHANICS