Methodology

This page documents exactly how every chart on this site is computed, so any result can be independently checked.

Ephemeris and coordinates

• Engine: Astronomy Engine (MIT license), an open-source planetary ephemeris based on modern analytical and numerical theories, accurate to roughly one arc-minute for the historical range this site supports.
• Positions: geocentric apparent ecliptic longitude, true equinox of date. Aberration and nutation are included as defined by the engine's apparent-position API.
• Zodiac: tropical. Sign index = floor(longitude / 30°), starting from Aries at 0°. Degree within sign = longitude mod 30. We do not compute sidereal, Vedic or Lahiri-ayanamsha charts.

Angles, houses and aspects

• Ascendant and Midheaven: derived from local sidereal time (from the Greenwich apparent sidereal time and your east-positive longitude), your latitude, and the obliquity of the ecliptic, by solving for the ecliptic points intersecting the eastern horizon and upper meridian.
• House systems: Whole Sign (default) and Equal House. We label them honestly — this site does not compute Placidus houses.
• Major aspects: conjunction 0°, sextile 60°, square 90°, trine 120°, opposition 180°. Orbs used for natal aspects are 8/4/6/6/8 degrees respectively; transit aspects use a tighter 1–3 degree window.
• Retrograde: determined from the sign of the planet's ecliptic longitude rate of change, sampled around the chart moment, with angle unwrapping across the 0°/360° boundary.

Time and time zones

Birth times are interpreted in the IANA time zone of the selected birth city. The engine resolves historical daylight-saving rules, flags non-existent local times (spring-forward gaps) and asks you to disambiguate repeated local times (fall-back overlaps) instead of silently guessing. For dates with no birth time, the site never invents an ascendant: angles and houses are shown as unavailable, and fast-moving placements such as the Moon are flagged with their possible range across the day.

Uncertainty display

Where a result depends on a missing or approximate input, the page says so: sign-boundary candidates ("could be A or B"), estimated-noon markers, and per-field reliability notes. No value is displayed with more precision than the inputs justify.

Interpretations

All meaning text is generated from rule templates bound to the actual computed placements — if your Venus is in Libra, the reading cites Venus in Libra. Interpretations summarize traditional Western astrology frameworks for entertainment and self-reflection. They are not scientific claims, medical, financial or relationship advice, and they never override your judgment.