Hipparchos or Hipparchus c.180-125BC
Greek astronomer and mathematician

Born in Nicaea, Bithynia, he made his observations from Rhodes where he spent a long time, and may also have lived in Alexandria. He compiled a catalogue of 850 stars (completed in 129BC) giving their positions in celestial latitude and longitude, the first such catalogue ever to exist, and this remained of primary importance up to the time of Edmond Halley. In comparing his observed star positions with earlier records he discovered the precession of the equinoxes. He observed the annual motion of the Sun, developed a theory of its eccentric motion and measured the unequal durations of the four seasons. He made similar observations of the Moon's more complex motion. Following the method of eclipse observations used by Aristarchos, he estimated the relative distances of the Sun and Moon and improved calculations for the prediction of eclipses. He developed the mathematical science of plane and spherical trigonometry required for his astronomical work. Hipparchos was the first to fix places on the Earth by latitude and longitude.