Ibn al-Shatir
Ibn al-Shatir most important astronomical treatise was "kitab nihayat al-sul fi tashih al-usul" ("The Final Quest Concerning the Rectification of Principles"). In it he drastically reformed the Ptolemaic models of the Sun, Moon and planets. His model incorporated the Urdi lemma, and eliminated the need for an equant by introducing an extra epicycle (the Tusi-couple), departing from the Ptolemaic system in a way that was mathematically identical (but conceptually very different) to what Nicolaus Copernicus did in the 16th century. This new planetary model was published in his work the "al-Zij al-jadid (The New Planetary Handbook.)"