The Almagest

 The Almagest is by far the most significant work in ancient astronomy. In a massive series of thirteen books, Ptolemy shows how every detail of the motions of the sun, moon, planets, and stars can be expressed using geometrical models that can be used to compute celestial positions with remarkable accuracy. The selection in this volume covers all the essential features of Ptolemy’s treatment of the heavens, omitting only more difficult and abstruse matters, such as the moon’s motion and the calculation of eclipses. In it, Ptolemy's theory of planetary motion is presented with explanations that are aimed at making it accessible to students encountering his work for the first time, while considering modern mathematical developments.