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Hipparchus (ca. 190 BC – ca. 120 BC) was a Greek astronomer, geographer, and mathematician of the Hellenistic period.
Hipparchus was born in Nicaea (now Iznik, Turkey), and probably died on the island of Rhodes. He is known to have been a working astronomer at least from 147 BC to 127 BC. Hipparchus is considered the greatest astronomical observer and, by some, the greatest overall astronomer of antiquity. He was the first Greek to develop quantitative and accurate models for the motion of the Sun and Moon. With his solar and lunar theories and his numerical trigonometry, he was probably the first to develop a reliable method to predict solar eclipses. His other achievements include the discovery of precession, the compilation of the first star catalogue of the western world, and, probably, the invention of the astrolabe.