Visible Diameter of a Heavenly Body

the angular diameter of a heavenly body, the angle from which the linear diameter of a heavenly body can be seen. It depends on the linear diameter and the distance to the heavenly body. The average visible diameter of the moon is 31′05″ (because of the ellipticity of the lunar orbit it varies from 29′24″ to 33′40″). The average visible diameter of the sun is 31′59″ (it varies from 31′27″ to 32′31″). The visible diameters of stars are extremely small, and only in a few stars do they attain several hundredths of a second.