private void ComputeMoonPosition()
{
double lp = 3.8104 + 8399.7091 * _epoch2000Centuries;
double m = 6.2300 + 628.3019 * _epoch2000Centuries;
double f = 1.6280 + 8433.4663 * _epoch2000Centuries;
double mp = 2.3554 + 8328.6911 * _epoch2000Centuries;
double d = 5.1985 + 7771.3772 * _epoch2000Centuries;
double longitude =
lp
+ 0.1098 * Math.Sin(mp)
+ 0.0222 * Math.Sin(2 * d - mp)
+ 0.0115 * Math.Sin(2 * d)
+ 0.0037 * Math.Sin(2 * mp)
- 0.0032 * Math.Sin(m)
- 0.0020 * Math.Sin(2 * f)
+ 0.0010 * Math.Sin(2 * d - 2 * mp)
+ 0.0010 * Math.Sin(2 * d - m - mp)
+ 0.0009 * Math.Sin(2 * d + mp)
+ 0.0008 * Math.Sin(2 * d - m)
+ 0.0007 * Math.Sin(mp - m)
- 0.0006 * Math.Sin(d)
- 0.0005 * Math.Sin(m + mp);
double latitude =
+0.0895 * Math.Sin(f)
+ 0.0049 * Math.Sin(mp + f)
+ 0.0048 * Math.Sin(mp - f)
+ 0.0030 * Math.Sin(2 * d - f)
+ 0.0010 * Math.Sin(2 * d + f - mp)
+ 0.0008 * Math.Sin(2 * d - f - mp)
+ 0.0006 * Math.Sin(2 * d + f);
longitude = InRange(longitude);
_sunEclipticLongitude = InRange(_sunEclipticLongitude);
MoonPhaseAngle = Math.Abs(longitude - _sunEclipticLongitude);
MoonPhaseAngle = InRange(MoonPhaseAngle);
double pip =
+0.016593
+ 0.000904 * Math.Cos(mp)
+ 0.000166 * Math.Cos(2 * d - mp)
+ 0.000137 * Math.Cos(2 * d)
+ 0.000049 * Math.Cos(2 * mp)
+ 0.000015 * Math.Cos(2 * d + mp)
+ 0.000009 * Math.Cos(2 * d - m);
double dMoon = 1.0 / pip; // Earth radii
// Moon position in Cartesian coordinates of the ecliptic coordinates system.
Vector3D moonPositionEcliptic = ToCartesian(dMoon, latitude, longitude);
// Moon position in Cartesian coordinates of the equatorial coordinates system.
Vector3D moonPositionEquatorial = EclipticToEquatorial * moonPositionEcliptic;
// To [m].
moonPositionEquatorial *= 6378.137 * 1000;
// Note: The moon formula is already corrected by precession.
MoonPosition = _equatorialToWorldNoPrecession.TransformPosition(moonPositionEquatorial);
}