astral.py 文件源码

def _eq_of_time(self, juliancentury):
        epsilon = self._obliquity_correction(juliancentury)
        l0 = self._geom_mean_long_sun(juliancentury)
        e = self._eccentrilocation_earth_orbit(juliancentury)
        m = self._geom_mean_anomaly_sun(juliancentury)

        y = tan(radians(epsilon) / 2.0)
        y = y * y

        sin2l0 = sin(2.0 * radians(l0))
        sinm = sin(radians(m))
        cos2l0 = cos(2.0 * radians(l0))
        sin4l0 = sin(4.0 * radians(l0))
        sin2m = sin(2.0 * radians(m))

        Etime = y * sin2l0 - 2.0 * e * sinm + 4.0 * e * y * sinm * cos2l0 - \
            0.5 * y * y * sin4l0 - 1.25 * e * e * sin2m

        return degrees(Etime) * 4.0