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.

本作品已被作者Fastfission释出到公有领域。这适用于全世界。 在一些国家这可能不合法；如果是这样的话，那么： Fastfission无条件地授予任何人以任何目的使用本作品的权利，除非这些条件是法律规定所必需的。

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)