ABSTRACT
Ptolemy’s most important astronomical works, the Almagest and the Handy Tables, had a large influence up until the end of the Middle Ages. Besides Ptolemy’s Handy Tables, numerous extant astronomical handbooks from Islamic, Byzantine and Western European origin contain a table for the equation of time. Astronomers from Antiquity and the Middle Ages knew that true solar time (as can be read from a sundial) and astronomical or mean solar time (which was used to determine the positions of the planets from tables) are not generally equal. Ptolemy expanded Hipparchus’s solar and lunar models and was the first to develop satisfactory models for the other planets. He compiled sets of tables for easy determination of planetary positions at arbitrary points in time. Neugebauer gives an extensive analysis of the equation of time as defined by Ptolemy and includes various examples of its calculation.
