Mapping

A map is a plot of radiation intensity as a function of position of the object in the sky. One of the coordinate systems, $(i)$ equatorial coordinate system, $(ii)$ elliptical coordinate system and $(iii)$ galactic coordinate system, is used to note the position of the object regardless of your position on the earth. A universally accepted coordinate system, the equatorial coordinate system (right ascension and declination) is normally used in radio astronomy.

From a map, the astronomer gets the information of the position of the emitting source and the structural details of the source. The structural details of the source in a map depends on the resolution of the radio telescope. (see section 1.2.1).