Mustafa ibn Ali al-Muwaqqit

Mustafa ibn Ali al-Muwaqqit (died 1571, the epithet al-Muwaqqit means "the timekeeper"), also known as Müneccimbaşı Mustafa Çelebi and Koca Saatçi, was an Ottoman astronomer and author of geography from the sixteenth century. Because of his works on the science of timekeeping and practical astronomy, he is considered "the founder of the Ottoman tradition" of those fields. He was one of the pioneers of astronomy literature in Ottoman Turkish—instead of Arabic which was more common in the Islamic world—following Muhammad al-Qunawi. Since his youth he served as the muwaqqit (religious timekeeper) attached to the Mosque of Selim I in Istanbul, in which capacity he produced most of his writing. In 1560 or later he was appointed to the office of müneccimbaşı, the highest post for astronomers of the Empire.