These are some slides I used in a seminar on space perception.

The moon looks larger when seen at the horizon than seen at the zenith although the size of the image that arrives at the eye does not change. But this is yet the beginning of the phenomenon. If you want to find out more, read the following pages:

1. The Phenomenon - Facts
2. Introduction
3. The Paradox
4. The Questions
5. In fact, the distance of the moon increases, when "moving" from the zenith to the horizon. Here is why.

Is more research neccessary? Yes, but not on the moon illusion!

M. Hershenson, 1989. The Puzzle Remains.
in Hershenson, M. The Moon Illusion.