Angular diameter
ANGULAR MEASUREMENT DESCRIBING HOW LARGE A SPHERE OR CIRCLE APPEARS FROM A GIVEN POINT OF VIEW
Angular size; Apparent size; Angular Size; Defect of illumination; Apparent diameter; Planetary Diameter; Angular radius; Planetary diameter; Planetary diameters; Angular diameter in astronomy; Angular width
The angular diameter, angular size, apparent diameter, or apparent size is an angular distance describing how large a sphere or circle appears from a given point of view. In the vision sciences, it is called the visual angle, and in optics, it is the angular aperture (of a lens).