celestial longitude vs angular distance

As nouns, angular distance is a hypernym of celestial longitude; that is, angular distance is a word with a broader meaning than celestial longitude:

• celestial longitude: (astronomy) the equatorial coordinate specifying the angle, measured eastward along the celestial equator, from the vernal equinox to the intersection of the hour circle that passes through an object in the sky; usually expressed in hours and minutes and seconds; used with declination to specify positions on the celestial sphere
• angular distance: the angular separation between two objects as perceived by an observer