Angular size
Angular size is a measurement of how large or small something is using rotational measurement. It is useful for measuring things that are so far away that they appear two dimensional.
Angular Size Media
Angular diameter: the angle subtended by an object
Diagram for the formula of the angular diameter
Approximate angles of 10°, 20°, 5°, and 1° for the hand outstretched at arm's length
A 19th century depiction of the apparent size of the Sun as seen from the Solar System's planets (incl. 72 Feronia and the then most outlying known asteroid, here called Maximiliana).
Comparison of angular diameter of the Sun, Moon and planets. To get a true representation of the sizes, view the image at a distance of 103 times the width of the "Moon: max." circle. For example, if this circle is 5 cm wide on your monitor, view it from 5.15 m away.
This photo compares the apparent sizes of Jupiter and its four Galilean moons (Callisto at maximum elongation) with the apparent diameter of the full Moon during their conjunction on 10 April 2017.
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