Shams al-Din Abu Abd Allah al-Khalili

Shams al-Dīn Abū ʿAbd Allāh Muḥammad ibn Muḥammad al-Khalīlī (Arabic: شمس الدين عبد الله محمد بن محمد الخليلي‎; 1320–1380) was a Mamluk-era Syrian astronomer who compiled extensive tables for astronomical use. He worked for most of his life as a religious timekeeper (muwaqqit) at the Umayyad Mosque in Damascus.[1] Little else is known about his life.

A table compiled by Al-Khalili showing the direction of qibla from various longitudes and latitudes.

Work

Al-Khalili is known for two sets of mathematical tables he constructed, both totaling roughly 30,000 entries. He tabulated all the entries made by the celebrated Egyptian Muslim astronomer Ibn Yunus, except for the entries that al-Khalili made himself for the city of Damascus. He computed 13,000 entries into his 'Universal Tables' of different auxiliary functions which allowed him to generate the solutions of standard problems of spherical astronomy for any given latitude. In addition to this, he created a 3,000 entry table that gave the direction of the city of Mecca (the Qibla) for all latitudes and longitudes for all the Muslim countries of the 14th century.[2] Knowledge of the direction of the Qibla is essential in Islam because Muslims pray in the direction of Mecca. The values present in al-Khalili’s tables have been determined to be accurate up to three or four significant decimal digits. Up to the present time, it is not known how exactly al-Khalili went about calculating each of his entries.[3]

References
  1. King, David A. (1975). "Al-Khalili's qibla table", Journal of Near-Eastern Studies 34(2), pp. 81-122.
  2. King, David A. (1973). "Al-Khalili's auxiliary tables for solving problems of spherical astronomy", Journal for the History of Astronomy 4(2), pp. 99-110.
  3. G Van Brummelen (1991). "The numerical structure of al-Khalili's auxiliary tables", Rivista Internazionale di Storia della Scienza (N.S.) 28(3), pp. 667-697.

Further reading
  • King, David A. (2007). "Khalīlī: Shams al‐Dīn Abū ʿAbdallāh Muḥammad ibn Muḥammad al‐Khalīlī". In Thomas Hockey; et al. (eds.). The Biographical Encyclopedia of Astronomers. New York: Springer. pp. 625–6. ISBN 9780387310220. (PDF version)
  • O'Connor, John J.; Robertson, Edmund F., "Shams al-Din Abu Abdallah Al-Khalili", MacTutor History of Mathematics archive, University of St Andrews.
  • King, David. A. (1970). "Khalīlī, Shams al-Dīn Abū ʿAbdallāh Muḥammad Ibn Muḥammad al-". Dictionary of Scientific Biography. New York: Charles Scribner's Sons. ISBN 0-684-10114-9.
  • Denis Roegel: An Extension of Al-Khalīlī's Qibla Table to the Entire World, 2008, INRIA technical report inria-00336090 (available on http://locomat.loria.fr)
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