A simple illustration showing the basic elements of Ptolemaic astronomy. It shows a planet rotating on an epicycle which is itself rotating around a deferent inside a crystalline sphere. The center of the system is marked with an X, and the earth is slightly off of the center. Opposite the earth is the equant point, which is what the planetary deferent would actually rotate around. Distances have been exaggerated as has the simplicity for the purposes of illustration.

Created by User:Fastfission in Adobe Illustrator.

This work has been released into the public domain by its author, Fastfission. This applies worldwide. In some countries this may not be legally possible; if so: Fastfission grants anyone the right to use this work for any purpose, without any conditions, unless such conditions are required by law.

If you want to credit someone, credit "Wikimedia Commons." Otherwise don't credit anyone, that's fine by me. --Fastfission 15:02, 14 April 2008 (UTC)