These are the similarities. The differences arise in the way the zodiac is configured. Vedic astrology uses a sidereal (star-focused) perspective and tropical astrology uses a seasonal focus. Western astrologers use a circular chart, while Vedic astrologers use a rectangular chart, which is of a different pattern in Northern India to that favoured in South India. Interestingly, recent discoveries show that ancient and mediaeval astrologers seem to have used a similar chart format; they show that Kepler used the tropical system, even though his charts looked like the North Indian style. Both systems use the zodiac, though the Vedic system is very Moon-oriented, while the tropical system is more Sun-oriented. The ascendant or rising sign is important in both. Vedic astrologers primarily use only the visible planets, Sun, Moon, Mars etc along with the Moon's nodes, Rahu and Ketu, which are given planetary status.

Western astrologers also employ the recently discovered outer planets (Uranus, Neptune and Pluto), along with other minor planets, including Chiron and several asteroids (Juno, Vesta, Ceres, Pallas Athena being the main ones). These planets are not visible to the naked eye, so were not considered by the ancients. Even so, there are references in some arcane texts to other planets, even, according to Cheiro, complete techniques for calculating the places of what are now known as the Outer Planets, Uranus, Neptune and Pluto. The Moon's nodes are not given as wide an acceptance by modern astrologers as they were by the more traditional Western practitioners, but they are still given significant weight by anyone who has studied them and their effects. The other difference is that Vedic astrologers make great use of the nakshatras, or lunar mansions. This has almost died out in the West, though, with the resurrection of mediaeval and ancient astrology, largely as a result of the laudable efforts of Project Hindsight, the lunar mansions are resurfacing as valid tools for a number of Westerners [see An Introduction to Hellenistic Astrology and The Living Signs both by Steven Birchfield on this site].
Another difference in approach lies in the idea that planets can be friends, enemies, or neutral to each other. This is a key factor in Vedic analysis, but is not really a consideration in the West. The methods used in forecasting are also different, with the Westerners using primarily transits and progressions of the planets, whereas the Jyotishis prefer a system of planetary periods, wherein each planet has a set period of influence, its dasha, which is also subdivided into sub-periods called bhuktis, where the dasha ruler is given assistant sub-rulerships from other planets in the periods of their bhuktis. This system has a historical correspondence in the West, with the ancient system of Alfridaries, or Alfridaria, seen on this site in the excellent article by Robert Hand, of Project Hindsight. There are other significant differences in approach, but the fundamental idea is common, namely that celestial events may be used as the tracking mechanism for events in the natural world, in human lives and their relationships.
The Prime Troublespot
The prime troublespot arises when we consider the relationship between the Signs and the constellations after which they are named. In the Tropical system, the first degree of Aries is designated as the time of the vernal equinox in the Northern Hemisphere. The first degree of Aries is considered the beginning of the zodiac in both systems. However, the time that this degree actually coincided with the vernal equinox (some two thousand years ago) has long passed, due to a cosmic phenomenon known as the precession of the equinoxes, which I will not discuss here in detail as it has been addressed well on this site by Kevin Burk in his article entitled Stars and Signs.
It is an error to consider the constellations to be the same as the signs. The signs are mathematical, 30 degree divisions of the zodiac that do not by any measure precisely coincide with the extension of the constellations in either the tropical or the sidereal systems. Signs are symbols, in both systems. Constellations are just fanciful names for star groupings, based originally in mythology (I leave aside here the lunar mansions, but the same argument applies to them). Skeptics regularly attempt to use this issue against astrology, but this merely displays ignorance on their part, an ignorance that we seek to dispel with this article.
Cosmic Being
Astrology is not about planets and constellations, it is about the interpretation of symbolic figures and their meanings in our lives. Each of these symbols and their mathematical interaction with each other are maps to consciousness, the cosmic consciousness that underpins the functionality and direction of our world. Since every part or unit of the cosmic being that comprises our world may be said to have some meaning and consciousness in itself, the key issue lies in the ability to organize this massive body of consciousness into sets of patterns that can be reliably and consistently interpreted. This has been achieved over the millennia by careful observation and correlation, leading today to the body of knowledge that we call Astrology. Whether the original discovery of astrology came by divine fiat, revelation, or just minute observation combined with an element of intuition is not the point. The point is, like any scientific endeavour, inspired original conceptions have been worked out in detail by massive numbers of individual “experiments” by countless ordinary astrologers that have tended to confirm rather than falsify the hypothesis in question. Moreover, at least in the West, astrological research is a constant, ongoing and growing endeavour, where new factors that are discovered, such as the outer planets, asteroids, galactic centre and the like are factored into the mix—and thanks to the marvellous computer, huge numbers of charts can be rapidly calculated and assessed with regard to the effects of these new factors on the lives of the beings that inhabit our world.
This is not to say that we should ignore the achievements of the past, nor that there is no ongoing development in Jyotish. Of course there is great benefit to be gained from exploring these traditional areas as well, and my Hyderabad friend and astrological researcher Ram Ramakrishnan is currently developing an extremely powerful computer program that takes new discoveries in Jyotish (and Western Astrology) and will provide a powerful tool for those who wish to know the future, so watch this space for developments. In the West, astrology received quite a drubbing in intellectual circles as a result of the heliocentric Copernican revolution that overthrew the Earth-centred Ptolemaic system, which was based on the ancient Aristotelian cosmology. This, combined with the growth of modern chemistry and its table of elements that seems to overthrow the ancient elemental approach of Fire, Air, Earth, Water and the Quintessence (Ether or Akasha), caused that astrological baby, along with its twin, the useful system of the humours in physiology, to be thrown out with the superstitious bathwater, in some circles at least that have now taken control of the education system in the West. This is of course a great pity, but recent scientific discoveries—including the possibility of action at a distance—are beginning to turn the tables once more. After all, the great scientists of the period of this turmoil, including the remarkable Kepler and even Newton himself, were also astrologers, often alchemists and certainly exceedingly interested in the inner workings of the world. To dismiss, as many have, the main body of work (ie the so-called “mystical delusions”) of these great men as irrelevant is again a serious and regrettable error that has led the world to the parlous state in which we find it today.
Back to the matter in hand. Vedic astrology and Western astrology have a common cause in helping the suffering masses of humanity to understand the nature of the world in which they live and the fact that the nature of existence is not as it seems but has a far deeper meaning than can be grasped from the materialistic, money-grubbing, “existence ends at death so get what you can now” approach fostered by the dominant intellectual perspective of this age. Both systems are equally good, with the Vedic style focusing more on an event-oriented, predictive approach and the tropical style focusing more on character and relationship analysis, though each system is good at both. In fact there is now something of a movement to combine the best of the two systems into a sort of fusion. This I think is laudable and is one of the reasons I had for starting our new site, http://www.truthstar.com
Article Source - http://www.astrologycom.com