This system became known as the "Ptolemaic system". It predicts the positions of the planets well enough for naked-eye observations, so it seemed accurate at the time. This is described in his book "Mathematical Syntaxis" (widely called the "Almagest"), a thirteen-book mathematical treatment of the phenomena of astronomy. It contains a wide variety of information ranging from earth conceptions to sun, moon, and star movement as well as eclipses and an explanation of the length of months. The "Almagest" also included a star catalog containing 48 constellations, using the names we still use today.