Measurements along the Celestial Sphere
Astronomers use degrees, minutes, and seconds to measure distances across the sky or sizes. These are referred to as Angular Sizes: the angle the object appears to span or distance between objects, for example:
- 60 arcseconds = 1 arcminute
- 60 arcminutes = 1 degree
The Sun and Moon appear to be about ½ degree as we see them from Earth. This is not their true size; it is just how they appear to us.
←→ ½ degree = 30 arcminutes
But in the “Real Universe” the Sun is 400 times bigger than the Moon!