Types of Moon Illusions

 

There are three types of moon illusions known to psychologists.  The first type is when the horizon moon appears angularly larger than the zenith moon, with both moons about the same distance away.  Hence, the horizon moon is necessarily of a larger perceived linear size. 

The second type of illusion occurs when both moons appear to be of the same linear size, but the horizon moon is perceived to be angularly larger.  It follows that the horizon moon is perceived to be closer to the observer.  The third type is a combination of the first and second.  Studies show that most people perceive the horizon moon to be angularly larger, linearly larger and closer.