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Related to right ascension: declination
right ascension,in astronomy, one of the coordinates in the equatorial coordinate systemequatorial coordinate system,
the most commonly used astronomical coordinate system for indicating the positions of stars or other celestial objects on the celestial sphere. The celestial sphere is an imaginary sphere with the observer at its center.
..... Click the link for more information. . The right ascension of a celestial body is the angular distance measured eastward from the vernal equinox along the celestial equator to its intersection with the body's hour circlehour circle,
in astronomy, a secondary axis in the equatorial coordinate system. The hour circle of a celestial body is the great circle on the celestial sphere that passes through both the body and the north celestial pole.
..... Click the link for more information. .
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right ascension(RA) Symbol: α. A coordinate used with declination in the equatorial coordinate system. The right ascension of a celestial body, etc., is its angular distance measured eastward along the celestial equator from the vernal (or dynamical) equinox, or more precisely from a catalog equinox, to the intersection of the hour circle passing through the body. It is generally expressed in hours (h), minutes (m), and seconds (s) from 0 to 24h: one hour equals 15° of arc.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006
right ascension[′rīt ə′sen·chən]
A celestial coordinate; the angular distance taken along the celestial equator from the vernal equinox eastward to the hour circle of a given celestial body. Abbreviated R.A.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.