Declination

Declination, angular distance of a heavenly body above the celestial equator in the equatorial coordinate system used by astronomers to describe the positions of objects in the sky. Declination (commonly abbreviated to Dec.) is measured in degrees (°), minutes (′) and seconds (′′) of arc from the celestial equator, a projection of Earth’s equator on to the celestial sphere. Objects on the celestial equator have Dec. 0° while those at the poles lie at Dec. 90°. Position to the east or west is given by the coordinates of right ascension. By convention, objects north of the celestial equator have declination prefaced by “+”, those to the south, “-”. For example, the prominent northern star Capella lies at Dec. + 38° 47′ 01′′, while Canopus in the southern sky is at Dec. - 52° 41′ 44′′. In the horizontal, or horizon, coordinate system, altitude is the equivalent of declination, and azimuth the equivalent of right ascension.