code: public double getSunLongitude()
      {
          // See page 86 of "Practial Astronomy with your Calculator",
          // by Peter Duffet-Smith, for details on the algorithm.
  
          if (sunLongitude == INVALID) {
              double[] result = getSunLongitude(getJulianDay());
              sunLongitude = result[0];
              meanAnomalySun = result[1];
          }
          return sunLongitude;
      }
docs: The longitude of the sun at the time specified by this object.
  The longitude is measured in radians along the ecliptic
  from the "first point of Aries," the point at which the ecliptic
  crosses the earth's equatorial plane at the vernal equinox.
  <p>
  Currently, this method uses an approximation of the two-body Kepler's
  equation for the earth and the sun.  It does not take into account the
  perturbations caused by the other planets, the moon, etc.
  @hide draft / provisional / internal are hidden on Android