Timocharis of Alexandria (circa 320 BC - 260 BC) was a Greek astronomer and philosopher. Likely born in Alexandria, he was a contemporary of Euclid.

In approximately 300 BC, with the help of Aristillus , he created the first star catalogue. Over 150 years later, Hipparchus would compare his own star catalogue to Timocharis' and discover that the longitude of the stars had changed over time, which led him to determine the first value of the precession of the equinoxes.

Timocharis was the first known astronomer to make a recorded observation of the planet Mercury, in 265 BC.

The Timocharis crater on the Moon is named in his honor.

External links

• Windows to the Universe: Discover Mercury
• The Astronomer Hipparchus of Rhodes - mentions Timocharis' contribution