Retro planets actually dont move back or they travel to previus signs its their relative motions compared to earth. sun has fix speed it does not varry but sometime speed of graha increases or decreases due to earths relative motions. retro planets get extra chesta bala which has to be interpreted differently in dasha and gochara. what wud like to add here is how to use retro planets . retro planets has its impotence when it again falls in star of another retro planets, rahu ketu are always retro hence if retro mars is rahu star cant be neglected. in muhurta we have to avoid star of retro planets it wud be best if we can avoid stars of even reto planets in natal chart. however it wud be dificult but a attempt can be made. next retro planets are very important in stellar astrology/kp astrology. in kp prashna astrology they consider failure of prashan if karak is in sub of retro planet. most important is retro effect of uranus neptune and pluto. they may remain retro for 5 months. and plays very big role in national or mundane astrology. where whole reading is based on 7 planets jup rahu ketu sat uranus neptune and pluto. lastly one whu uses sarvotabhadra chakra for transit , annual or mundane astrology. if any planet is retro its speed get vary than normal. accordingly its aspect or vedha will be left right or straight.. here rahu ketu are exceptions. if we dont consider retro planets then we can not interpret sarvatobhadra chakra . www.astromihir.com