Ptolemy's Almagest is a 2nd century AD Ancient Greek mathematical and astronomical treatise on the complex motions of the stars and planetary paths. The Almagest is a critical source of information on ancient Greek astronomy. The Caption reads: "Ptolemy's Star Catalogue, from a late Latin version of the Almagast, 1490. A line of text locates each star within its constellation. Lattitudes measured from the ecliptic are constant, but because of precession the writer of this text has given three longitudes: one for the time of Ptolemy, the first century AD, another for the time of Adam, set at 349BC and the third for the mid fifteenth century when this copy was made. The crude pictures contrast oddly with the precision of the mathematical data."