Hipparchus

Hipparchus lived approximately between the years 190 BCE and 120 BCE. He was a Greek mathematician and astronomer.Hipparchus is considered by many to be the greatest astronomer of ancient times. He is credited with discovering the Precession of the Equinoxes (a consequence of the Earth's precession), and used Apollonius of Perga's idea of Deferents and Epicycles to explain planetary retrograde motion.Hipparchus is said to have used a total solar eclipse in Egypt to determine the Earth - Moon distance to within 4% accuracy.Hipparchus is also thought to have developed the mathematical subject of trigonometry, and put together the first true star catalog of western civilization.Hipparchus was honored recently by having the satellite Hipparcos named after him. This satellite used highly precise optics and the technique of trigonometric (stellar) parallax to accurately determine the distance to stars out to a distance of about 1600 light-years.