right ascension


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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.
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. 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.
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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.

right ascension

[′rīt ə′sen·chən]
(astronomy)
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.
References in periodicals archive ?
For the rate with which the right ascension varies, it is given in the Explanatory Supplement to the American Ephemeris and the Nautical Almanac 1961,
The calibration routine will issue a series of move commands in right ascension and declination and then re-center the guide star.
The 14th-magnitude star, LHS 1140, is located near right ascension 0h 45m, declination--15[degrees] 14' in the constellation Cetus, the Whale.