Definition
Right ascension is the angular distance measured eastward along the celestial equator from the vernal equinox to the hour circle of a point. It is expressed in time units: 24h = 360°, so 1h = 15°.
Use with declination
Together with declination (δ), RA specifies a direction on the sky independent of observer location — ideal for star catalogues and telescope mounts (when precession is accounted for).
