The World by Homer. 1886 replica of a map of the known world according to the Ancient Greek astronomer Claudius Ptolemaeus (c.90-c.168), also known as Ptolemy. Ptolemy is one of the most famous astronomers of antiquity. The geocentric (Earth-centred) Ptolemaic system described in his Almagest documented previous Greek thought, and dominated Western science for over a thousand years. The Almagest summarised five centuries of Greek astronomy and represented the conventional view of the Universe until the Copernican revolution. He also worked out distances and sizes for the Sun and the Moon, compiled a catalogue of 1028 stars and described various astronomical instruments.