11. Ptolemy moved the observation point explicitly off the center of the deferent to the equant. 12. That seems to contradict Deferent and epicycle. 13. Astronomers responded by introducing the deferent and epicycle, which caused a planet to vary its distance. 14. This article describes absolutely deferent company than the one previously deleted for the lack of notable references. 15. Ptolemy did not predict the relative sizes of the planetary deferents in the " Almagest ". 16. Newtonian or classical mechanics eliminated the need for deferent / epicycle methods altogether and produced more accurate theories. 17. Only after Kepler's refinement of Copernicus'theory was the need for deferents and epicycles abolished. 18. The " Syntaxis " adopted Hipparchus'solar model, which consisted of a simple eccentric deferent . 19. All of his calculations were done with respect to a normalized deferent , considering a single case at a time. 20. It was the use of equants to decouple uniform motion from the center of the circular deferents that distinguished the Ptolemaic system.
