[Observation] Retrograde only at opposition, when brightest [Modeling mechanism] Radii of epicycles aligned to Sun-Earth line [Object(s)] 
Exterior 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