The discussion surrounding Ptolemy’s star catalog is a fascinating one. While astronomers for hundreds of years took Ptolemy’s catalog as authoritative, Tycho Brahe noticed that the positions of the stars had a $\approx 1º$ error in longitude. To explain this, Brahe hypothesized that this was due to Ptolemy stealing the data for the star catalog from Hipparchus and updating the longitudes with an incorrect constant of precession.
Astronomers have been debating this ever since.
In this series of posts, I review the scholarly history surrounding Ptolemy’s star catalog. This series is largely based on Gerd Grasshoff’s $1990$ book The History of Ptolemy’s Star Catalogue, but will include some additional sources and discussion that occurred after Grasshoff’s book was released.
For those that don’t want to read this detailed history, I have an article at Universe Today summarizing the discussion.