An introduction to coordinate systems used in Astronomy

From Wikipedia:

In geometry, a coordinate system is a system which uses one or more numbers, or coordinates, to uniquely determine the position of the points or other geometric elements on a manifold such as Euclidean space.

There are numerous coordinate systems currently being used in Astronomy, some of which are listed below:


RA (right ascension) and DEC (declination) are the longitudes and latitudes of the sky. RA corresponds to east / west direction, analogous to longitude, while DEC measures north / south directions, analogous to latitude.


World Coordinate System (WCS) is a set of transformations that map pixel locations in an image to their real-world units, such as their position on the sky sphere. These transformations can work …