Astronomy

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Almagest

Astronomical and mathematical encyclopedia compiled c. AD 140 by Ptolemy. It served as the basic guide for Arab and European astronomers until the 17th century. The name derives from the Arabic for “the greatest.” Its 13 books cover such topics as the geocentric (Earth-centred), or Ptolemaic, model of the solar system; eclipses; the coordinates and sizes of certain fixed stars; and the distances to the Sun and the Moon.

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