Question

A person on earth is observing the moon which is

238,860
miles away. The moon is a diameter of
2160
miles. What is the angle in degrees spanned by the moon's image in the eye of the beholder?

Answer 1

As the moon's diameter is straight, the distance from the observer to the moon and the diameter are at 90°, subtending an angle at the viewer's eye. This is:
tan∅ = diameter / distance
tan∅ = 2160 / 238,860
∅ = 0.52°