Frontispiece of Regiomontanus' "Epitome of the Almagest" depicting Ptolemy and Regiomontanus sitting beneath an armillary sphere. Claudius Ptolemy (90-168 AD), was a Greek-Roman mathematician, astronomer, geographer, and astrologer. His astronomical treatise, the Almagest, is the only surviving comprehensive ancient treatise on astronomy. Few details of Ptolemy's private life are known for certain. Johannes Muller von Konigsberg (June 6, 1436 - July 6 1476) best known as Regiomontanus, was a German mathematician, astronomer, astrologer, translator, and Catholic bishop. He was a pupil and friend of Georg von Peurbach. Peurbach began to prepare a summary and commentary on the Almagest. He died after completing only six books and Regiomontanus continued the task. When it was published in 1496, the Epitome of the Almagest made the highest levels of Ptolemaic astronomy widely accessible to European astronomers for the first time. He died of unknown causes in 1476 at the age of 40.