>>22941947 (OP)Astronomers who have recently re examined Ptolemys original data soon realized that retrocalculations of the planets proved that many of Ptolemys so called observations were wrong.
The errors were gross even by the standards of ancient astronomy that there is also no longer any doubt that Ptolemy plagiarized the work of the earlier Hipparchus.
the earlier star catalogue compiled by Hipparchus conducted his observations from the island of Rhodes.
This Greek island lies five degrees of latitude north of Alexandria (where Ptolemy was).
This makes for a five degree band of southern stars that can be seen from Alexandria but not from Rhodes.
Not a single one of the 1022 stars that Ptolemy listed in his catalogue is to be found in this five degree band.
Moreover, every example given in the Almagest of how to work out spherical astronomy problems is given for a latitude the same as that of Rhodes.
all his own observations are fraudulent, so far as we can test them.
Many of the observations that he attributes to other astronomers are also fraud that he has committed.
His work is riddled with theoretical errors and with failures of comprehension.
His models of the moon and Mercury conflict violently with elementary observation and must be counted as failures.
in rejecting the earlier belief that the planets revolved around the Sun, Ptolemy was responsible for preventing the advance of astronomy for a millennium.
Ptolemy also has caused us to lose much of the genuine work in Greek astronomy and it would have been better for astronomy had the Almagest never been written.