Methodology
How We Calculate
Every chart at Astreya stands on reference-grade astronomical standards - the same ones used by professional astrology software. Accuracy under 0.01°.
Planetary positions - Swiss Ephemeris (JPL DE431)
All planetary positions are computed with Swiss Ephemeris, the reference astronomical library built on NASA's JPL DE431 ephemerides. Accuracy is under 0.01° (under 36 arc-seconds) for every planet - the same standard used by professional software such as Solar Fire and astro.com.
Houses - Placidus
The Western natal chart uses the Placidus house system, the most widely adopted standard in modern Western astrology, dividing the ecliptic by the rising/setting time of each degree. The Vedic module uses Whole Sign houses, as prescribed by the Jyotish tradition.
Vedic module - Lahiri ayanamsa
Vedic calculations (Rashi, Nakshatra, Vimshottari Dasha) use the official Lahiri (Chitrapaksha) ayanamsa adopted by the Indian government - the offset between the tropical and sidereal zodiacs, currently about 24°.
Chiron - JPL Horizons
Chiron is computed directly from NASA's JPL Horizons system with cubic Hermite interpolation between daily values - accuracy comparable to professional observatory ephemerides.
Chinese zodiac - solar terms
The Eastern horoscope determines the animal sign and element by the exact astronomical solar terms (Lichun, ~February 4), not January 1st or the lunar new year - as prescribed by the classical Chinese calendar.
Human Design - standard bodygraph mechanics
The Human Design chart follows standard mechanics: the 88° solar offset before birth for the Design side, 64 gates on the I Ching wheel, 9 centers, 36 channels, with activations computed to 0.01°.
Aspects - standard orbs
Conjunction (0°), sextile (60°), square (90°), trine (120°) and opposition (180°) with orbs up to 8° for Sun/Moon and 6° for the remaining planets - the conservative values accepted in the Western tradition.
Time-zone correction
Time zones are resolved from the IANA tz database with full daylight-saving and historical-change coverage, so the birth time is always converted to exact UTC before any calculation.
See also: Glossary of terms · About Astreya