How Starsigns computes your chart
Ephemeris
All planetary positions come from the Swiss Ephemeris (Astrodienst), the professional standard used by working astrologers, accurate to fractions of an arc-second across 1800–2399. The website and the Starsigns iOS app run the same engine on the same data files, so a chart computed here is identical in the app.
Time and place
Birth times are interpreted in the historical timezone of the birthplace using the IANA time zone database — including old daylight-saving rules (a 1977 UK birth is correctly treated as British Summer Time, not GMT). Coordinates come from the place you select, not a city-center guess of our own.
Houses and points
Houses use the Placidus system; the Ascendant and Midheaven are computed directly from the exact time and location. Sign positions are tropical.
Aspects and orbs
Conjunction and opposition within 8°, square and trine within 7°, sextile within 5°, quincunx within 3°. Aspect lines on the wheel are colour-coded by family: hard aspects in pink, flowing in mint, quincunx in lavender.
What astrology is — and isn’t
Astrology is a symbolic language, not a science; charts are for reflection and entertainment, not medical, financial, or legal decisions. What we promise is that the computation is exact: the planets really were where your chart says they were.