Published 1898â€"1907, this three-part collection, edited by the Danish philologist Johan Ludvig Heiberg (1854â€"1928), contains the extant astronomical works in Greek of Ptolemy, active in second-century Alexandria. Volume 2 (1907) contains Ptolemy's shorter astronomical works, notably Hypotheseis ton planomenon, his planetary hypotheses, along with a substantial Latin prolegomena.