# Angular size

Also called: arcminute, arcsecond, degree, apparent size.

How big something looks, as an angle: degrees (°), arcminutes (′, 1/60°) and arcseconds (″, 1/60′).

We can't measure sky objects in kilometres by eye, so we measure the angle they span. The full Moon is about 31′ (half a degree); Jupiter about 45″; the Andromeda Galaxy over 3°; the components of a close [double star](https://astropilot.space/glossary/double-star) can be 1″ apart.

Your hand is a ready ruler at arm's length: a little finger covers about 1°, three middle fingers about 5°, a fist about 10°.

**In AstroPilot:** Every object page gives its size and compares fields of view with the full Moon.

**Examples:** [M31](https://astropilot.space/object/M31.md), [jupiter](https://astropilot.space/object/jupiter.md), [moon](https://astropilot.space/object/moon.md), [M57](https://astropilot.space/object/M57.md)

**Related:** [Separation](https://astropilot.space/glossary/separation.md), [True field of view](https://astropilot.space/glossary/true-field.md), [Resolution](https://astropilot.space/glossary/resolution.md)

From the AstroPilot astronomy glossary: https://astropilot.space/glossary/angular-size