Astro*Dictionary
by Michael Erlewine

2 articles for
"Deferent"

Old term from Ptolemaic astronomy referring to an imaginary orbiting point about which a body moves in an epicycle.

 

See also:
♦ Epicycle

In Ptolemaic astronomy, an imaginary orbit pursued by a celestial body, around which another body moved in an epicycle (q.v.). A deferent was employed in conditions wherein the natural motion of the body was not involved. The term reflects the fact that Ptolemy was ignorant of the Earth's motion.

 

See also:
♦ Epicycle