Vedic Astrology: An Introduction

Please note: astrology is a traditional belief system and an important part of Indian religious and cultural life. It is not a science: controlled tests of astrological predictions, including studies carried out in India with practising astrologers, have not shown that they perform better than chance. This page describes how Jyotisha astrology works and how it relates to Indian astronomy, for educational purposes only. It does not offer predictions or advice.

Jyotisha as a Vedanga

Jyotisha is one of the six Vedangas, the auxiliary disciplines of the Vedic tradition. In its earliest form, the Vedanga Jyotisha attributed to Lagadha, it is a calendar manual: it tells priests how to track the Sun and Moon through the nakshatras in order to schedule sacrifices. It contains no horoscopes. Horoscopic astrology developed later, in the early centuries of the Common Era, when Indian scholars absorbed and adapted Hellenistic astrology — the Yavanajataka ("Horoscopy of the Greeks"), a Sanskrit versification by Sphujidhvaja, is one of the earliest surviving examples — and combined it with indigenous elements such as the nakshatras.

The three skandhas

By the time of Varahamihira (sixth century CE), Jyotisha was described as having three skandhas, or branches:

• Siddhanta (also called Ganita or Tantra) — mathematical astronomy: computing the positions of the Sun, Moon and planets, eclipses, sunrise, and the elements of the calendar. This is the branch that produces the Panchangam and the branch to which the great Indian astronomers contributed.
• Samhita — "collection": omens and natural phenomena affecting communities and kingdoms, such as weather, rainfall, comets, earthquakes and harvests, as well as architecture and other practical lore. Varahamihira's Brihat Samhita is the classic example.
• Hora — horoscopy: interpreting a chart cast for the moment of a person's birth (jataka), choosing times for undertakings (muhurta), and answering questions from the chart of the moment a question is asked (prashna). Important texts include Varahamihira's Brihat Jataka, Kalyanavarman's Saravali, Mantreshvara's Phaladeepika and the Brihat Parashara Hora Shastra, attributed to the sage Parashara, whose present form is relatively late.

The sidereal zodiac and the rashis

Jyotisha divides the ecliptic — the Sun's apparent path — into twelve rashis of 30 degrees each. Unlike Western astrology, which measures the zodiac from the March equinox (the tropical zodiac), Jyotisha measures it from a point fixed among the stars (the sidereal zodiac). Because of the slow precession of the Earth's axis, the two zodiacs drift apart by about one degree every 72 years; the gap, called the ayanamsa, is now about 24 degrees. As a result, the Sun's sidereal sign is usually one sign "behind" its Western tropical sign. Each rashi is traditionally assigned a ruling graha: