What the engine measures

These entries document AstroStella’s calculation parameters: the house system the site sends, the five aspects and their orbs, the retrograde speed test, and the source of the longitudes (Swiss Ephemeris, DE431). This is not a general astrology dictionary.

By

Last updated

Calculate a natal chart · The 12 signs

  • Birth chart

    A birth chart on AstroStella is a Swiss Ephemeris natal calculation: date, latitude, longitude, and Placidus houses by default.

  • Big three

    AstroStella’s big three are three longitudes: the Sun, the Moon, and the Ascendant. Only the Sun is stable from a date alone.

  • Ascendant

    The Ascendant is the ecliptic longitude on the eastern horizon. AstroStella computes it from birth time, latitude, and longitude, then labels its 30° sign.

  • Placidus

    AstroStella’s public birth chart posts houseSystem PLACIDUS. The ephemeris also implements WHOLE_SIGN, EQUAL, and KOCH.

  • Conjunction

    AstroStella records a conjunction when two planets are within 8° of a 0° separation. No two different zodiac signs have centers 0° apart.

  • Sextile

    The sextile is the only major aspect in AstroStella’s engine with a 6° orb. The angle is 60°. Every other major aspect uses 8°.

  • Square

    AstroStella records a square at 90° with an 8° orb. The two Mercury-ruled signs, Gemini and Virgo, are one of those exact 90° pairs.

  • Trine

    A trine in AstroStella’s engine is 120° with an 8° orb. Same-element signs sit on this angle: fire with fire, earth with earth, air with air, water with water.

  • Opposition

    An opposition in AstroStella’s engine is 180° with an 8° orb. Six sign pairs sit on that angle, including Aries opposite Libra.

  • Retrograde

    AstroStella marks a body retrograde when its ecliptic speed is negative. The flag is isRetrograde from that speed, not from a sign’s reputation.

  • Transit

    A transit in AstroStella compares a natal chart with planetary positions at a later time, using the same aspect angles and orbs as the natal pairs.

  • Moon phase

    AstroStella’s moon-phase calculation returns a 0–1 phase, an illumination percent, and the next new, full, and quarter moons.

  • Synastry

    Synastry on AstroStella is a comparison of two birth charts. Each person needs a date, a latitude, and a longitude. It is not a sign-to-sign essay.

  • Solar return

    A solar return is the moment the Sun returns to its natal ecliptic longitude. AstroStella computes it for a year from the natal date and place.

  • Swiss Ephemeris

    AstroStella computes planetary longitudes with the Swiss Ephemeris and JPL DE431 data. Sign pages and the birth chart use those longitudes, not rounded sun-sign tables.