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For the Moon, Ptolemy began with Hipparchus' epicycle-on-deferent, then added a device that historians of astronomy refer to as a "crank mechanism": [28] he succeeded in creating models for the other planets, where Hipparchus had failed, by introducing a third device called the equant. Ptolemy wrote the Syntaxis as a textbook of mathematical ...
In Ptolemy's era the boundaries of the zodiac signs were close to those of the visible constellations whose names they bear, but Ptolemy demonstrates the theoretical distinction between the two frames of reference in describing the starting point of the zodiac as fixed, not to the stars, but to the mathematically calculated vernal equinox. [57]
Ptolemy's Handy Tables (Ancient Greek: πρόχειροι κανόνες, romanized: Procheiroi kanones) is a collection of astronomical tables that second century astronomer Ptolemy created after finishing the Almagest. The Handy Tables elaborated the astronomical tables of the Almagest and included usage instructions, but left out the ...
Originating from the Thebaid region of Upper Egypt, he worked at Alexandria and wrote works on astronomy including the Almagest, the Planetary Hypotheses, and the Tetrabiblos, as well as the Handy Tables, the Canobic Inscription, and other works unrelated to astronomy. Ptolemy's Almagest (originally titled The Mathematical Syntaxis) is one of ...
Ptolemy's work the Almagest had wide and long-lasting acceptance and influence for over a millennium. He gave a geometrical lunar theory that improved on that of Hipparchus by providing for a second inequality of the Moon's motion, using a device that made the apparent apogee oscillate a little – prosneusis of the epicycle.
The angular rate at which the epicycle traveled was not constant unless he measured it from another point which is now called the equant (Ptolemy did not give it a name). It was the angular rate at which the deferent moved around the point midway between the equant and the Earth (the eccentric) that was constant; the epicycle center swept out ...
c. 150 CE – Claudius Ptolemy completes his work Almagest, that codifies the astronomical knowledge of his time and cements the geocentric model in the West, and it remained the most authoritative text on astronomy for more than 1,500 years.
Ptolemy emphasised that the epicycle motion does not apply to the Sun. His main contribution to the model was the equant points. He also re-arranged the heavenly spheres in a different order than Plato did (from Earth outward): Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn and fixed stars, following a long astrological tradition and the ...