Definition

ANGULAR DISTANCE west of a CELESTIAL MERIDIAN, the arc of the CELESTIAL EQUATOR, or the angle at the CELESTIAL POLE, between the UPPER BRANCH of a CELESTIAL MERIDIAN and the HOUR CIRCLE of a CELESTIAL BODY or the VERNAL EQUINOX, measured westward through 24 HOURS (360°). It is usually further designated as local, Greenwich,or sidereal, as the origin of measurement is the LOCAL or GREENWICH MERIDIAN, or the HOUR CIRCLE of the VERNAL EQUINOX.