The Moon Illusion Demonstration.
This is only a demonstration, or cartoon of the actual illusion. But it is fun to move the Moon around and see for yourself how it might appear to change size in the night sky.

     In this demonstration, the Moon will follow your mouse across the sky from horizon to zenith.
     About 85% percent of the population can see this illusion in nature. Most observers say the moon looks about ½ times larger when it is close to the horizon.