Astronomy is the foundation of Astrology. Study of Planets and its movements form the very basis of prediction. Cave-Man with all his inquisitiveness has been following Sun and Moon. Initially it was about following Sun and Moon to understand the migration path and locate predators, later is was used for his own planning. The earliest known Moon calendar & precision of moon's movement is found engraved in caves. Lunar and Solar eclipse figure in most holy scriptures. The fact that people with certain health conditions & pregnant women were asked not to get exposed to eclipse was known hundreds of years ago. Primitive man, though was primitive in many ways, had precisely followed the movement of planets. Perhaps with the complete use of senses and with some great seers and Maharishis to think beyond senses, ancient Indians not only studied the planets, but also mastered its impact on human life.
Astrology was considered scholarly, was followed by eminent scientists and was practiced by most intellectual people on this planet. With some significant advancement in the last century, Astrology has been challenged by many eminent people. There have been questions about how a planet in a particular zodiac sign can act very differently from being in a different zodiac sign. Also because of huge variation in distance between earth-planet and earth-stars, position of a planet in a constellation was further questioned. While answers to these questions is beyond this article, the most simple way to prove this is by meeting the right astrologer who can give accurate predictions
Sun as the central figure predominates the entire celestial system and so is the case in horoscope and predictions. Nine planets are considered while charting the horoscope. "Planet" here is a body that is close to earth and exerts sufficient force on earths surface. It is beyond the scope of this article to debate on the nature of force viz : Gravitational, Magnetic or Electro Magnetic, while it is suffice to say that Maharishis could comprehend this force. Scientific community might understand this force in the near future. Sun, Moon, Mercury, Venus, Mars, Jupiter,Saturn and two shadowy planets Rahu and Ketu form the nine planets. Any new planet which might be discovered in due course of time is not going to impact the Astrological predictions in a significant manner
For the purpose of Horoscope and calculation, Earth is considered as the centre, and Horoscope is the position of planets in the zodiac as seen from the reference point on earth at that particular instant. Zodiac is a broad band in the heavens, an imaginary circle of 360 degree , which represent the path of the sun as seen from the Earth. This circle is divided into 12 equal parts , 12 rasi or 12 zodiac signs. The ecliptic is marked by 27 constellations. It is not that there are exactly 27 constellations when observed from Earth, rather the pivotal 27 are considered for the charts. Each rasi extends 30 degrees (360/12) and each Constellation extends 13 degree 20 minutes(360/27) on the arc. Each rasi is often referred as House (or) Bhava in a typcial astrologers language. This diagram shows 12 houses with Mesha Rasi as the starting point. Aswani,Bharani, Krithika mentioned in brackets are the stars that occupy Mesha Rasi
Nadi Astrology, practised in TamilNadu and Kerala, goes a few steps further. According to Nadi system, there are 150 Nadi's in a sign, which make it a total of 1800 Nadis (150 * 12). The degrees for each Nadi are not equal. The similarity with the established system of Parashara Horoscope ends here. The basis of prediction based on these Nadi are not clearly available, hence Astrologers fail to predict when they do not find the right text. Ancient Seers, are said to have understood the science in detail, and they have written thousands of manuscripts for various Nadis. These are supposed to be far more accurate than the established system of prediction. Re-birth is central to Nadi Astrology and our deeds in this birth are supposed to be equating that of our experiences in the previous Birth. Varga Chakra D60 in Vedic Astrology gives light on the experiences from previous birth