First Night Out Series: Measuring Distances In The Sky

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:

  • The width of your little finger is about one degree—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 five degrees.
  • A closed fist is about ten degrees.
  • If you spread out your fingers, the distance from the tip of your first finger to the tip of your little finger is 15 degrees.
  • If you spread out your fingers, the distance from little finger to thumb covers about 25 degrees of sky.

Measuring degrees with your hands.

With a bit of practice, this hand system is endlessly useful when measuring your way around the sky.

Calibrating with the Big Dipper

Everyone's hands are slightly different, so you might want to practice and calibrate your own hand measurements using the Big Dipper.

Big Dipper Distances.

Here are the rough distances from Dubhe to several other prominent Big Dipper stars:

Dubhe to Merak 5 degrees
Dubhe to Megrez 10 degrees
Dubhe to Alioth 15 degrees
Dubhe to Mizar 20 degrees
Dubhe to Alkaid 25 degrees

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