Methodology & accuracy
How we calculate
Every position is computed in your browser using open astronomical algorithms (astronomy-engine, VSOP87/ELP-based), in the true equinox and ecliptic of date frame — the same default as the Swiss Ephemeris.
How accurate is it?
- Planets: versus the Swiss Ephemeris, the maximum deviation over 60 random dates is 18 arcseconds (Sun: 2″).
- Houses: all seven house systems (Placidus, Koch, Regiomontanus, Campanus, Porphyry, equal, whole sign) match at 0 arcseconds over 80 random places and times.
- Lunar node: the true (osculating) node deviates ≤ 40″; the mean Lilith ≈ 7′ (definitions of the “mean apogee” differ).
- Chiron, Ceres, Pallas, Juno, Vesta: NASA/JPL Horizons (DE441) 5-day tables with cubic interpolation, 1900–2100, ~1″ error.
- Time zone: the birthplace is converted to universal time with the IANA database’s historical rules (daylight saving, local mean time).
- Vedic: Lahiri ayanamsa; Vimshottari dasha with a 365.25-day year.
- Chinese: month and year boundaries come from the Sun’s true longitude (jie terms); the day pillar from the Julian-day sexagenary cycle.
What it cannot do
Astrology does not predict: scientific tests have not confirmed predictive power. We use it as a symbolic language for self-reflection and openly state the scientific status. An error in birth time affects the Ascendant and houses (about 0.25° per minute).