Measuring the distance from one star to another in the sky is easy when you master using your hands to measure the degrees between objects.
Hold your hand at arm’s length (in front of your face with a straight hand):
- The width of your little finger is about 1° – enough to cover the moon and sun, both of which are each half a degree across.
- The width of the first three fingers side-by-side spans about 5°.
- A closed fist is about 10°.
- If you spread out your fingers, the distance from the tip of your first finger to the tip of your little finger is 15°.
- If you spread out your fingers, the distance from little finger to thumb covers about 25° of sky.
With a bit of practice, this hand system is endlessly useful when measuring your way around the sky.