Who was Hipparcus?

Answer 1

Hipparchus (ca. 190 BC - ca. 120 BC) was a Greek astronomer, geographer, and mathematician of the Hellenistic period.

Hipparchus is considered the greatest ancient astronomical observer and, by some, the greatest overall astronomer of antiquity. He was the first Greek whose quantitative and accurate models for the motion of the Sun and Moon survive.

With his solar and lunar theories and his trigonometry, he may have been the first to develop a reliable method to predict solar eclipses. His other reputed achievements include the discovery of precession, the compilation of the first comprehensive star catalog of the western world, and possibly the invention of the astrolabe, also of the armillary sphere which first appeared during his century and was used by him during the creation of much of the star catalogue.