Hold your little finger out at arm’s length. Can you cover the disk of the Moon? The Moonprojects an angular size of 30′ (half a degree); your finger should more than cover it. Youcan use this fact...

Hold your little finger out at arm’s length. Can you cover the disk of the Moon? The Moon projects an angular size of 30′ (half a degree); your finger should more than cover it. You can use this fact to make some basic sky measurements. As a simple rule, your little finger at arm’s length is about 1° across, your middle three fingers are about 4° across, and your clenched fist is about 10° across. If the constellation Orion is visible, use this information to estimate the angular size of Orion’s belt and the angular distance between Betelgeuse and Rigel. Compare your findings with Figure 0.2(a).