Vedas are the oldest literature and compendium of multitude of Knowledge. The history of Astrology traces back to Vedic times, lakhs of years ago from now. Astrology can be divided broadly as Siddhanta Bhaga (Calculation part) and Phalita Bhaga (Predictive part). In Rigveda, the year is divided into 12 months, the special 13th month called extra month correlates the Solar and Lunar months. In Taittireeya Brahmana, the 6 seasons are described. The details of planets as gods, solar and lunar eclipses are available in Rigveda.
There are 18 pioneers in Astrology, who contributed for its development. They are: 1. Surya, 2. Pitamaha, 3. Vyasa, 4. Vasishta, 5. Atri, 6. Parasara, 7. Kasyapa, 8. Narada, 9. Garga, 10. Mareechi, 11. Manu, 12. Angeerasa, 13. Lomasa, 14. Poulisa, 15. Chyavana, 16. Yavana, 17. Bhrigu, and 18. Saunaka.
Varahamihira (123 AD) wrote 'Brihat Samhita', a great work on Astronomy and Astrology. There are 105 chapters and 4000 verses in this book. He has shown how Astrology can be applied for the welfare of public.
Aryabhatta-I (476 AD) wrote 'Aryabhateeya', which comprise a great deal of Astronomy, Mathematics and Astrology. Even Astronomy of this book is spread to Arab countries. Aryabhatta-II (950 AD) wrote 'Mahasiddhanta', where he explained more clearly about calculation part of Astrology.
Bhaskara-I (629 AD) wrote 'Mahabhaskareeya', a book on astro-mathematics. Bhaskara-II (1114 AD) gave 'Siddhanta Siromani' where a lot of Mathematics can be found. Details of square, square root, cube, cube root, factorial values, factors of a number are explained. Details of planets, calculation of radius of earth , eclipses, and atmospheric layers ( 7 zones) above earth are discussed clearly.
Indian Astrology links the planets and stars with gods. Gods are representatives of certain types of energies. There are 4 things to be done in a human life: Dharma (righteous path), Artha (wealth), Kaama (Desire), Moksha (Unification of soul with God). These are one by one represented by the 12 houses of the zodiac. The hidden meaning is: A man should follow righteous path to achieve wealth and fulfill his desires. At the same time he must be desirous to reach God, and find ways to finally unify himself with the super soul. The potentiality to achieve this is represented step wise by the zodiac.
Theory says that Zodiac wheel starts with Aries 0 degrees, and is constant. When a top is rotating , it bends slightly and rotates. If a point is imagined on the top , it make circles. These circles will not coincide each other. There will be some deviation between each circle. Similarly, the Zodiac is also deviating slowly from its constant position. It is calculated to be around 51 seconds per year. This deviation is called Precession of equinoxes, or Ayanamsa. Indian Astrologers are not taking this Ayanamsa into account when they calculate Planet positions. So their system is called 'Nirayana'. But westerners apply this correction in their calculations. So western system is called 'Sayana' system. This is the major difference in Indian and Western Astrological worlds.
Sayana = Nirayana + Ayanamsa.
There are 27 stars and each star has 4 padas (quarters). Thus a total of 27 x 4 = 108 star padas will will arise, which have been distributed in the zodiac. Since 12 signs are there in the Zodiac, every sign gets 9 padas. Each pada is of 3 degrees 20 minutes duration and 9 x 3deg 20min = 30 degrees. So each sign takes 30 degrees duration.
There are planets whose role is to bestow the results of past deeds, done either in this birth or carried from previous births. Planets merely transmit the results which we earlier stored in the form of radiation. There are 9 planets identified: Sun, Moon, Mars, Jupiter, Saturn, Mercury, Venus , Rahu (Ascending Node) and Kethu (Descending Node). All the planets are not comfortable in all the signs. A planet is comfortable in its exaltation, or friendly or own house. Then it may give good results. A planet is not comfortable in enemy camp, and can give bad results.
Each planet aspects its opposite planet, i.e, the house and planet in 7th from it. Additionally, Jupiter has 5th and 9th aspects. Mars has 4th and 8th aspects. And, Saturn has 3rd and 10th aspects.
By observing the inter-relationships between the signs, planets, stars and their positions, we can understand the inherent capabilities of a human being, his thought process, and his weaknesses, and finally conclude what he has in store for his future. Various Dasa- systems are developed to know what planets are currently influencing a human being and promoting him to do what kind of things.
Indians call planets 'Grahas'. Graha means that which catches. Grahas are those which catch the human beings and shed their influence on them. Grahas affect all inanimate and animate objects in this world. This is the reason Grahas are also personified as gods by Indians. Another greatness of Indian Astrology lies in providing remedial measures for various problems faced by human beings. The remedies are mentioned by sages in various works and also in Vedas. But the suitability of a remedy for a case is to be judged by a competent astrologer.
Indians see Astrology in every thing. It became a part and parcel of their culture. For them Astrology is 'VedaChakshu', the guiding eye for molding their future and attaining self- realization.