Ptolemy lists the declination of 18 stars as recorded by Timocharis or Aristillus in roughly the year 290 BC.
[3] The observed stellar passage by Venus may have occurred on October 12, 272 BC when the planet came within 15 arcminutes of the star η Virginis.
Hipparchus was able to deduce the period during which Timocharis made his observations based upon the records of earlier lunar eclipses.
From this difference, Hipparchus discovered that the longitudes of the stars had changed over time, which led him to determine the first value of the precession of the equinoxes as no less than 1/100° per year.
[7] Galileo assigns to Arsatilis[8] and Timocharis the origin "third opinion" on the number of heavens, namely that there were nine heavens, seven for the planets, one for the daily movement of the firmament from east to west, and another for the slower motion from west to east, while crediting Hipparchus, Agrias, Milaeus and Ptolemy with improving the model.