Sidereal zodiac
Indian JyotishaCross-traditionEditorial synthesisAstronomical factTraditional doctrine
Definition
The zodiac convention that anchors the twelve signs to the fixed stars rather than to the seasons. It is standard in Indian Jyotisha; the offset from the tropical zodiac is called the ayanamsha.
Also called: Fixed-star zodiac · Nirayana zodiac (Jyotisha)
In more depth
Sidereal systems keep the signs aligned with reference stars, so a sidereal chart differs from a tropical chart of the same moment by the current tropical-sidereal offset. Indian Jyotisha, whose canonical natal texts include Varāhamihira's Brihat Jataka, uses sidereal reckoning.[1][2]
The divergence between the two conventions grows from axial precession, a measured astronomical cycle of roughly 25,800 years. Neither convention is 'wrong': they are different definitions, and several ayanamsha values are in use, so a sidereal chart must state which one it applies.[3]
References
Numbered citations in the text link to the records below; each record links to the full source registry.
- Varāhamihira. The Brihat Jataka of Varaha Mihira. N. Chidambaram Iyer (translator). 1885. Historical primary source View source record
- Nicholas Campion. A History of Western Astrology, Volume I: The Ancient and Classical Worlds. Continuum. 2009. Historical scholarship View source record
- NASA Science. Milankovitch (Orbital) Cycles and Their Role in Earth's Climate. 2020 (last updated 2024). Astronomical fact View source record