Khalīlī was an astronomer associated with the Umayyad Mosque in the center of Damascus. A colleague of the astronomer Ibn al‐Shāṭir, he was also a muwaqqit – i. e., an astronomer concerned withʿilm al‐mīqāt, the science of timekeeping by the Sun and stars and regulating the astronomically defined times of Muslim prayer. Khalīlī’s major work, which represents the culmination of the medieval Islamic achievement in the mathematical solution of the problems of spherical astronomy, was a set of tables for astronomical timekeeping. Some of these tables were used in Damascus until the 19th century, and they were also used in Cairo and Istanbul for several centuries. The main sets of tables survive in numerous manuscripts, but they were not investigated until the 1970s.
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