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.

Quest'opera è stata rilasciata nel pubblico dominio dal suo autore, Fastfission. Questa norma si applica in tutto il mondo. In alcuni paesi questo potrebbe non essere legalmente possibile. In tal caso: Fastfission garantisce a chiunque il diritto di utilizzare quest'opera per qualsiasi scopo, senza alcuna condizione, a meno che tali condizioni siano richieste dalla legge.

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)