Best known for his 1906 discovery of lost texts in the Archimedes Palimpsest, Danish scholar Johan Ludvig Heiberg (1854-1928), professor of classical philology at Copenhagen, published numerous editions of ancient mathematicians, including Archimedes and Apollonius of Perga (also reissued in this series). Between 1898 and 1907, he published in three parts the extant astronomical works of Ptolemy, active in second-century Alexandria. The Ptolemaic system, his geocentric model of the universe, prevailed in the Islamic world and in medieval Europe until the time of Copernicus. Volume 2, published in 1907, contains a brief preface and a substantial prolegomena in Latin, followed by the Greek text of Ptolemy's shorter astronomical works, including Phaeis aplanon asteron, a treatise on the phenomena of the fixed stars, and Hypotheseis ton planomenon, his planetary hypotheses representing the most influential statement of his geocentric model, provided here with a facing-page translation into German.