[Observation] Retrograde motion [Modeling mechanism] Motion of epicycle in same direction as deferent. Period of epicycle is time between retrograde motions (synodic period). [Object(s)] 
Planets
S t a r s
S u n
M o o n
T h e 5 p l a n e t s
P l a n e t s
I n t e r i o r p l a n e t s
E x t e r i o r p l a n e t s