Definition:Azimuth (Astronomy)

Definition
Let $X$ be a point on the celestial sphere.

The spherical angle between the principal vertical circle and the vertical circle on which $X$ lies is the azimuth of $X$.

The azimuth is usually measured in degrees, $0 \degrees$ to $180 \degrees$ either west or east, depending on whether $X$ lies on the eastern or western hemisphere of the celestial sphere.