Jyotiṣa — Vedic astrology
The Bṛhat Parāśara Horā Śāstra and the sidereal tradition
The core textbook attributed to Parāśara, the Bṛhat Parāśara Horā Śāstra, is a composite: scholarship dates its older part to roughly 600–750 CE and its later part a little after, though Parāśara is cited as an authority even earlier. The 27 nakshatras are far older, rooted in the Vedic period. The system is sidereal — measured from the fixed stars — and the standard Indian ayanamsha, Lahiri (Chitrapaksha), was fixed by the Government of India's Calendar Reform Committee in 1955.
What it measures
The chart in the sidereal zodiac, the Moon's nakshatra (one of 27 lunar mansions), the Vimshottari daśā (a 120-year cycle of planetary periods keyed to that nakshatra), the five limbs of the panchāṅga (the day's lunar calendar), and the divisional charts (vargas).
Where practitioners disagree
- Which ayanamsha sets the sidereal zero?
Lahiri / Chitrapaksha (the Indian government standard, ours), Fagan–Bradley, Raman, Krishnamurti and others
The ayanamshas place the sidereal zero a degree or more apart — an unresolved dispute that shifts every position.
This engine: Lahiri (Chitrapaksha) by default, Fagan–Bradley selectable.
Sources
- David Pingree, Jyotiḥśāstra: Astral and Mathematical Literature
- Calendar Reform Committee (India), Report (1955)