What do astronomers mean by declination and ascension?

1 Answer
Dec 13, 2015

Declination is the angle of an object from the equator and right ascension is the angle of the object eastwards measured in hours.


Astronomers use a spherical coordinate system to measure the positions of a planet, star, galaxy or other object. This requires two coordinates which are called declination and right ascension.

Declination is the angle that the object makes with the equatorial plane in the North-South direction. It is measured in degrees. The angle is positive if the object is North of the equator and negative if it is South of the equator. It is the celestial equivalent of latitude.

Right ascension is a bit more complex because of the rotation of the Earth. It is the angle the object makes in an Eastward direction along the equatorial plane. The origin in the direction of the Vernal Equinox which is a reference direction for Astronomers. The right ascension angle is not measured in degrees. It is measured in hours where 360 degrees equals 24 hours. It is the celestial equivalent of longitude.