Right ascension (RA) is one of the two celestial coordinates used in the equatorial coordinate system to specify the position of an object in the sky. The other coordinate is declination (Dec). Right ascension is analogous to longitude on Earth and measures the angular distance of an object eastward along the celestial equator from a reference point known as the vernal equinox.
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Right ascension is the eastward angular coordinate measured around the celestial equator from the reference equinox. It is often quoted in hours, with 24 hours corresponding to a full turn.