WordNet (r) 3.0 (2006):

celestial longitude
    n 1: (astronomy) the equatorial coordinate specifying the angle,
         measured eastward along the celestial equator, from the
         vernal equinox to the intersection of the hour circle that
         passes through an object in the sky; usually expressed in
         hours and minutes and seconds; used with declination to
         specify positions on the celestial sphere; "one hour of
         right ascension equals fifteen degrees" [syn: right
         ascension, RA, celestial longitude]