Ptolemy of Alexandria Ptolemy of Alexandria was the most influential astronomer of the ancient world. The books and theories Ptolemy developed served as a major basis for future astronomers. It was during the Renaissance period that his work became thoroughly studied and revised. Ptolemy collected all ancient knowledge of astronomy and geography including it in his book Almagest around 140 A.D. It follows, he then wrote a four volume astrological study known as the Tretrabiblos. Ptolemy claimed that the scribes of Babylon had been instructed since 750 B.C to keep detailed astronomical diaries. These diaries were written for seven hundred years on clay ta