What is the size of the moon?

A proof that this effect is an illusion is to establish size relativity in both situations: both near the horizon and in a high position in the sky. When the moon is near the horizon, holding a small coin at arm's length with one eye closed, positioning it next to the moon, and comparing the size of the coin relative to the size of the moon reveals its relative size for that given situation. Then, when the moon is higher in the sky, positioning the coin next to it again will confirm that the moon looks the same size in both positions.