Hipparchus also determined the first inequality of the moon, the equation of the centre.

He adopted the theory of epicycles and eccentrics, a geometrical conception for the purpose of resolving the apparent motions of the heavenly bodies on the principle of circular movement.

He also undertook to make a catalogue of the stars by the method of alineations--that is, by indicating those that are in the same apparent straight line.

The number of stars so catalogued was 1,080.

If he thus attempted to depict the aspect of the sky, he endeavored to do the same for the surface of the earth, by marking the position of towns and other places by lines of latitude and longitude.