Geocentric longitude

Longitude \Lon"gi*tude\, n. [F., fr. L. longitudo, fr. longus
   long.]
   1. Length; measure or distance along the longest line; --
      distinguished from {breadth} or {thickness}; as, the
      longitude of a room; rare now, except in a humorous sense.
      --Sir H. Wotton.
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            The longitude of their cloaks.        --Sir. W.
                                                  Scott.
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            Mine [shadow] spindling into longitude immense.
                                                  --Cowper.
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   2. (Geog.) The arc or portion of the equator intersected
      between the meridian of a given place and the meridian of
      some other place from which longitude is reckoned, as from
      Greenwich, England, or sometimes from the capital of a
      country, as from Washington or Paris. The longitude of a
      place is expressed either in degrees or in time; as, that
      of New York is 74[deg] or 4 h. 56 min. west of Greenwich.
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   3. (Astron.) The distance in degrees, reckoned from the
      vernal equinox, on the ecliptic, to a circle at right
      angles to the ecliptic passing through the heavenly body
      whose longitude is designated; as, the longitude of
      Capella is 79[deg].
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   {Geocentric longitude} (Astron.), the longitude of a heavenly
      body as seen from the earth.

   {Heliocentric longitude}, the longitude of a heavenly body,
      as seen from the sun's center.

   {Longitude stars}, certain stars whose position is known, and
      the data in regard to which are used in observations for
      finding the longitude, as by lunar distances.
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