Methodology
How we calculate and interpret astrology charts
How birth data becomes chart positions, houses, aspects, forecasts, and an interpretation—with uncertainty kept visible.AstroMaster keeps astronomical calculation separate from astrological interpretation. The same date, time, place, time zone, zodiac, and house system should always reproduce the same positions. Their symbolic meaning is an interpretive framework, not a scientific diagnosis or a guaranteed prediction.Last updated · Aug 24, 2026Inputs and time handling
Charts use the date, local clock time, and place you provide, plus the historical time-zone rules in effect on that date. When a birth time is approximate or unknown, we say so.
- The Ascendant, Midheaven, house cusps, and house placements depend heavily on birth time.
- Historical daylight saving time and time-zone changes can shift the converted moment.
- A place name alone isn't enough. You also need coordinates and the time-zone rule for that date.
Calculation layer
The AstroMaster engine uses Swiss Ephemeris data to calculate planetary positions, angles, houses, and aspects from the normalized moment and chart settings. Display preferences never change your saved birth data.
- Natal, synastry, transit, progressed, return, event, horary, and electional charts each use their own chart type and settings.
- Aspect results depend on the enabled aspect set and orb policy.
- Switching house systems changes house cusps and house placements, but not a planet's zodiac longitude.
Interpretation layer
Interpretations combine calculated chart facts with a stated astrological tradition and editorial framework. AI may help organize or draft text, but it doesn't replace calculation, source review, or the uncertainty rules shown to readers.
- We keep calculated facts separate from interpretation.
- Personalized content should draw on your actual natal chart, not just your Sun sign.
- Health, legal, financial, and safety decisions require qualified professional advice.
Reproducibility and limits
The same inputs and settings should reproduce the same chart. Display rounding may differ slightly, and a different time zone, house system, zodiac, or orb setting can produce legitimate differences.
- Unknown birth time: don't rely on angles or houses.
- Approximate birth time: test a time range before interpreting fast-moving angles.
- Birth time rectification: treat the result as a hypothesis. It can't independently prove the original birth time.
External references
- Swiss Ephemeris documentationTechnical reference for the astronomical ephemeris used by the calculation engine.
- IANA Time Zone DatabaseReference for historical civil time-zone rules.
- Astrodienst Charts FAQPublic reference for chart inputs and birth-time sensitivity.