private static Distance GetMoonDistance(DateTime d, double[] values)
{
//Ch 47
double JDE = JulianConversions.GetJulian(d); //Get julian
double T = (JDE - 2451545) / 36525; //Get dynamic time.
double D = values[1];
double M = values[2];
double N = values[3];
double F = values[4];
double dist = 385000.56 + (MeeusTables.Moon_Periodic_Er(D, M, N, F, T) / 1000);
return(new Distance(dist));
}
private static DateTime Get_Soltice_Equinox_From_JDE0(double JDE0, double offset)
{
//Get Event Ch 27.
double T = (JDE0 - 2451545.0) / 36525;
double W = (35999.373 * Math.PI / 180) * T - (2.47 * Math.PI / 180);
double ang = 1 + .0334 * Math.Cos(W) + .0007 * Math.Cos(2 * W);
double sum = MeeusTables.Equinox_Solstice_Sum_of_S(T);
double JDE = JDE0 + ((.00001) * sum / ang);
DateTime?d = JulianConversions.GetDate_FromJulian(JDE);
if (d.HasValue)
{
return(JulianConversions.GetDate_FromJulian(JDE).Value.AddHours(offset));
}
return(new DateTime()); //Julian limit exceeded, return empty DateTime
}
/// <summary>
/// Get moons lat/long in radians (Ch 47).
/// </summary>
/// <param name="LDMNF">L,D,M,N,F</param>
/// <param name="T">Dynamic Time</param>
/// <returns>Lat[0], Long[1]</returns>
private static double[] Get_Moon_Coordinates(double[] LDMNF, double T)
{
//Reference Ch 47.
double lat = LDMNF[0] + (MeeusTables.Moon_Periodic_El(LDMNF[0], LDMNF[1], LDMNF[2], LDMNF[3], LDMNF[4], T) / 1000000);
double longi = MeeusTables.Moon_Periodic_Eb(LDMNF[0], LDMNF[1], LDMNF[2], LDMNF[3], LDMNF[4], T) / 1000000;
lat %= 360;
if (lat < 0)
{
lat += 360;
}
//Convert to radians
double l = rad * lat; // longitude
double b = rad * longi; // latitude
return(new double[] { l, b });
}
/// <summary>
/// Gets moon distance (Ch 47).
/// </summary>
/// <param name="d">DateTime</param>
/// <param name="offset">UTC offset in hours</param>
/// <returns>Distance</returns>
public static Distance GetMoonDistance(DateTime d, double offset)
{
//Ch 47
offset *= -1;
double julianOffset = offset * .04166667;
double JDE = JulianConversions.GetJulian(d) + julianOffset; //Get julian
double T = (JDE - 2451545) / 36525; //Get dynamic time.
double[] values = Get_Moon_LDMNF(T);
double D = values[1];
double M = values[2];
double N = values[3];
double F = values[4];
//Ch 47 distance formula
double dist = 385000.56 + (MeeusTables.Moon_Periodic_Er(D, M, N, F, T) / 1000);
return(new Distance(dist));
}
//v1.1.3 Formulas
//The following formulas are either additions
//or conversions of SunCalcs formulas into Meeus
/// <summary>
/// Grabs Perigee or Apogee of Moon based on specified time.
/// Results will return event just before, or just after specified DateTime
/// </summary>
/// <param name="d">DateTime</param>
/// <param name="md">Event Type</param>
/// <returns>PerigeeApogee</returns>
private static PerigeeApogee MoonPerigeeOrApogee(DateTime d, MoonDistanceType md)
{
//Perigee & Apogee Algorithms from Jean Meeus Astronomical Algorithms Ch. 50
//50.1
//JDE = 2451534.6698 + 27.55454989 * k
// -0.0006691 * Math.Pow(T,2)
// -0.000.01098 * Math.Pow(T,3)
// -0.0000000052 * Math.Pow(T,4)
//50.2
//K approx = (yv - 1999.97)*13.2555
//yv is the year + percentage of days that have occured in the year. 1998 Oct 1 is approx 1998.75
//k ending in .0 represent perigee and .5 apogee. Anything > .5 is an error.
//50.3
//T = k/1325.55
double yt = 365; //days in year
if (DateTime.IsLeapYear(d.Year))
{
yt = 366;
} //days in year if leap year
double f = d.DayOfYear / yt; //Get percentage of year that as passed
double yv = d.Year + f; //add percentage of year passed to year.
double k = (yv - 1999.97) * 13.2555; //find approximate k using formula 50.2
//Set k decimal based on apogee or perigee
if (md == MoonDistanceType.Apogee)
{
k = Math.Floor(k) + .5;
}
else
{
k = Math.Floor(k);
}
//Find T using formula 50.3
double T = k / 1325.55;
//Find JDE using formula 50.1
double JDE = 2451534.6698 + 27.55454989 * k -
0.0006691 * Math.Pow(T, 2) -
0.00001098 * Math.Pow(T, 3) -
0.0000000052 * Math.Pow(T, 4);
//Find Moon's mean elongation at time JDE.
double D = 171.9179 + 335.9106046 * k -
0.0100383 * Math.Pow(T, 2) -
0.00001156 * Math.Pow(T, 3) +
0.000000055 * Math.Pow(T, 4);
//Find Sun's mean anomaly at time JDE
double M = 347.3477 + 27.1577721 * k -
0.0008130 * Math.Pow(T, 2) -
0.0000010 * Math.Pow(T, 3);
//Find Moon's argument of latitude at Time JDE
double F = 316.6109 + 364.5287911 * k -
0.0125053 * Math.Pow(T, 2) -
0.0000148 * Math.Pow(T, 3);
//Normalize DMF to a 0-360 degree number
D %= 360;
if (D < 0)
{
D += 360;
}
M %= 360;
if (M < 0)
{
M += 360;
}
F %= 360;
if (F < 0)
{
F += 360;
}
//Convert DMF to radians
D = D * Math.PI / 180;
M = M * Math.PI / 180;
F = F * Math.PI / 180;
double termsA;
//Find Terms A from Table 50.A
if (md == MoonDistanceType.Apogee)
{
termsA = MeeusTables.ApogeeTermsA(D, M, F, T);
}
else
{
termsA = MeeusTables.PerigeeTermsA(D, M, F, T);
}
JDE += termsA;
double termsB;
if (md == MoonDistanceType.Apogee)
{
termsB = MeeusTables.ApogeeTermsB(D, M, F, T);
}
else
{
termsB = MeeusTables.PerigeeTermsB(D, M, F, T);
}
//Convert julian back to date
DateTime date = JulianConversions.GetDate_FromJulian(JDE).Value;
//Obtain distance
Distance dist = GetMoonDistance(date);
PerigeeApogee ap = new PerigeeApogee(date, termsB, dist);
return(ap);
}
