335?-405?

Greek mathematician and astronomer who wrote a commentary on Ptolemy's Algamest that also provides information on older lost books. A member of the Museum of Alexandria, Theon produced rewritings of texts by earlier authors. His version of Euclid's Elements was more popular than the original, but he added errors that were to remain for centuries. His lost works include texts on an astronomical instrument (the astrolabe), omens, and the rising of the Nile. He was the father of Hypatia.