Little is known of Hipparchus’ life, but he is known to have been born in Nicaea in Bithynia. The town of Nicaea is now called Iznik and is situated in north-western Turkey. Despite being a mathematician and astronomer of great importance, Hipparchus’ work has not been well documented; only one work of his has survived, namely Commentary on Aratus and Eudoxus. Most of his discoveries have been made known to us only through Ptolemy’s Almagest. His contributions to the field of mathematics include producing a trigonometric table of chords, introducing the division of a circle into 360˚  into Greece, calculating the length of the year within 6.5' and discovering precession of the equinoxes.