Ibn al-Shatir

Ibn al-Shatir
Born	1304
Died	1375 (aged 71)
Occupation	Astronomer

Ibn al-Shatir or Ibn ash-Shatir (Arabic: ابن الشاطر‎‎; 1304–1375) was an Arab astronomer. He worked as muwaqqit (موقت, religious timekeeper) in the Umayyad Mosque in Damascus and constructed a magnificent sundial for its minaret in 1371/72.

His 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, eliminating the eccentric and equant by introducing extra epicycles.

Although his system was firmly geocentric (he had eliminated the Ptolemaic eccentrics), the mathematical details of his system were identical to those in Copernicus's De revolutionibus. It is unknown whether Copernicus read ibn al-Shatir.

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