How to Calculate Angular Size
What is Angular Size?
Angular size (apparent size in sky) depends on object actual size and distance: θ ≈ size / distance (small angle approximation).
Step-by-Step Guide
- 1Input actual size and distance
- 2Calculate angular size in degrees, arcminutes, or arcseconds
- 3Compare to other celestial objects
Worked Examples
Input
Moon: ~3476 km diameter, 384,000 km distance
Result
Angular size ≈ 0.52° (match Sun size, hence solar eclipses)
Common Mistakes to Avoid
- ✕Confusing angular and actual size
- ✕Forgetting distance effect on apparent size
Frequently Asked Questions
Why do Moon and Sun look same size?
Coincidence: Sun 400× larger but 400× farther away.
Ready to calculate? Try the free Angular Size Calculator
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