Celestine API Documentation - v0.2.1
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    Function greenwichMeanSiderealTime

    • Calculate Greenwich Mean Sidereal Time from Julian Date

      Uses the IAU 1982 formula from Jean Meeus "Astronomical Algorithms". Returns GMST in degrees (0-360).

      GMST tells you what Right Ascension is currently on the Greenwich meridian. It's needed for calculating the Ascendant and house cusps.

      Parameters

      • jd: number

        Julian Date (UT)

      Returns number

      Greenwich Mean Sidereal Time in degrees (0-360)

      "Astronomical Algorithms" by Jean Meeus, Chapter 12, page 88

      // J2000.0 epoch (January 1, 2000, 12:00 UT)
      greenwichMeanSiderealTime(2451545.0)
      // Returns: ~280.46° (18h 42m)

      // Calculate for a specific date
      const jd = toJulianDate({ year: 2024, month: 6, day: 15, hour: 0, minute: 0, second: 0 });
      const gmst = greenwichMeanSiderealTime(jd);

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