Jyotiṣa is one of the Vedāṅga-( Part of Ancient Hindu Scripture called Veda ) the six auxiliary disciplines used to support Life with Vedic rituals. Early jyotiṣa is concerned with the preparation of a calendar to determine dates for sacrificial rituals. There are mentions of eclipse-causing “demons” in the Atharvaveda and Chāndogya Upaniṣad, the latter mentioning Rāhu (a shadow entity believed responsible for eclipses and meteors The term graha, which is now taken to mean the planet, originally meant demon The Ṛigveda also mentions an eclipse-causing demon, Svarbhānu, however, the specific term graha was not applied to Svarbhānu until the later Mahābhārata and Rāmāyaṇa
The foundation of Hindu astrology is the notion of the Vedas (Ancient Hindu scriptures), which is the connection between the microcosm and the macrocosm. The practice relies primarily on the sidereal zodiac, which differs from the tropical zodiac used in Western (Hellenistic) astrology in that an ayanāṃśa adjustment is made for the gradual precession of the vernal equinox. Hindu astrology includes several nuanced sub-systems of interpretation and prediction with elements not found in Hellenistic astrology, such as its system of lunar mansions (Nakṣatra). It was only after the transmission of Hellenistic astrology that the order of planets in India was fixed in that of the seven-day week. Hellenistic astrology and astronomy also transmitted the twelve zodiacal signs beginning with Aries and the twelve astrological places beginning with the ascendant.