Vedic  astrology and western astrology have vast differences in their presumptions,  methodologies and results. Which one originated earlier and whether one of them  influenced the other are the questions no one can answer for certain today.  Without lending into that controversy we will outline important differences in  the two systems, which are as follows:
                            - 
                                Different  Zodiacs: 
 Western astrologers generally use Tropical Zodiac based on  equinoxes whereas Vedic astrologers use Sidereal Zodiac based on fixed stars.  This gives different positions to many planets and we get a different  horoscope.
- House  Cusps: 
 In western astrology beginning of the house is treated as the  cusp while in Vedic astrology it is in the middle of the house. It may cause a  difference in many house placements.
- Aspects: 
 Western  astrology recognizes only square, trine and sextile aspects and it is based on  exact degrees of planets. Aspects here are only between planets or planets to  special points like Ascendant and mid-heaven. In Vedic astrology planets in one  sign aspect other signs or planets in the forward direction only. Strength of  aspect is measured in a certain way. Then there are special aspects of some  planets like Mars, Jupiter and Saturn.
- 	Timing Methodology: 
 In western astrology, progression or transit is the only  means to time events. In Vedic astrology there is a fully developed dasa  system. Dasas have no reference to transit but are interpreted only in the  birth horoscope and divisional charts. There are general purpose Dasas,  conditional Dasas and special purpose Dasas. Then there are planetary Dasas  like Vimshottari dasa and Rasi Dasas like Chara dasa.
- 	Lunar Nodes: 
 Vedic astrology recognizes lunar nodes as Rahu and Ketu and  even dasa years have been assigned to them treating them shadowy planets.  Western astrology talks of north nodes (correlated with Jupiter) and south node  (correlated with Saturn).
- Vargas  or Harmonic Charts: 
 Varga charts are unknown to western astrology but  are extensively used in Vedic astrology. If ‘time of birth’ is correct up to  minute, different charts for different activities of life can be devised  correctly. There is Navamsa chart for spouse and general purposes, Dasamsa for  profession, Dwadasamsa for parents, Vimsamsa for spiritual life and so on. This  is very important in predictive Vedic astrology. Importance of Vargas can be  realized by the fact that the main birth chart remains same for 2 hours on an  average while Vargas change even within 2 minutes.
- 	Other differences: 
 There are some other important differences  also. Like sun is benefic in western astrology but a malefic or cruel planet in  Vedic astrology. Besides, sun sign is very important in western astrology  unlike Vedic astrology. Extra- Saturnine planets Uranus, Neptune and Pluto used  in western astrology find no mention in Vedic astrology classics. On the other  hand, Vedic astrology uses Upagrahas or Aprakash grahas like Dhoom, Vyatipat,  Chaap, Parivesh, Gulika, Mandi etc not known in western astrology. Finally,  Vedic astrology recognizes some yogas like Gajakesari yoga which are important  in chart interpretations.