How much did Hipparchus estimate the stars moved relative to the equinoxes?

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Engraving of six astronomers, with Hipparchus seated at center and, from left to right, Galileo, Johannes Hevelius, Tycho Brahe, Nicolaus Copernicus, and Ptolemy standing, each holding scientific instruments. — Hipparchus “Six astronomers,” the frontispiece of *Astronomica Institutio* (1692) by Jan Luyts, engraving after drawing by Gerard Hoet. Hipparchus is seated at center with from left to right: Galileo, Johannes Hevelius, Tycho Brahe, Nicolaus Copernicus, and Ptolemy.

By comparing his own observations of stars near the ecliptic with recorded observations from approximately 150 years prior, Hipparchus discovered that these stars had moved about 2° relative to the equinoxes.1

Based on this and further analysis, he deduced that the fixed stars move eastward at a rate of not less than 1° in 100 years. This discovery led to his identification of precession, the gradual shift in the orientation of Earth's axis.21