||An astronomical coordinate system for indicating the positions of celestial objects
on the celestial sphere. The system consists of two components, right ascension and
declination. Right ascension is the angle between the vernal equinox and the point
where the hour circle intersects the celestial equator. The right ascension is always
measured eastward from the vernal equinox, in the units of hours, minutes, and seconds.
Declination is the angle between the celestial equator and the position of the star
measured along the star's hour circle. It is measured in degrees, minutes, and seconds
north or south of the celestial equator. By definition, the vernal equinox is located
at right ascension 0h and declination 0°. Equatorial coordinates change with time
due to the precession of the Earth's rotation axis.