//Static methods
/////////////////////////////// Implementation ////////////////////////////////
public static double MeanGreenwichSiderealTime(double JD)
{
//Get the Julian day for the same day at midnight
DT date = new DT();
date.SetJD(JD, DT.AfterPapalReformJD(JD));
double[] D = date.Get();
int Year = (int)D[0];
int Month = (int)D[1];
int Day = (int)D[2];
int Hour = (int)D[3];
int Minute = (int)D[4];
double Second = D[5];
date.Set(Year, Month, Day, 0, 0, 0, date.InGregorianCalendar());
double JDMidnight = date.Julian();
//Calculate the sidereal time at midnight
double T = (JDMidnight - 2451545) / 36525;
double TSquared = T * T;
double TCubed = TSquared * T;
double Value = 100.46061837 + (36000.770053608 * T) + (0.000387933 * TSquared) - (TCubed / 38710000);
//Adjust by the time of day
Value += (((Hour * 15) + (Minute * 0.25) + (Second * 0.0041666666666666666666666666666667)) * 1.00273790935);
Value = CT.D2H(Value);
return(CT.M24(Value));
}
//Static methods
////////////////////////////////// Implementation /////////////////////////////
public static double DeltaT(double JD)
{
//Construct a CAADate from the julian day
DT date = DT.CreateJD(JD, DT.AfterPapalReformJD(JD));
double y = date.FractionalYear();
double T = (y - 2000) / 100;
double Delta;
if (y < 948)
{
Delta = 2177 + (497 * T) + (44.1 * T * T);
}
else if (y < 1620)
{
Delta = 102 + (102 * T) + (25.3 * T * T);
}
else if (y < 1998)
{
int Index = (int)((y - 1620) / 2);
Debug.Assert(Index < GFX.DeltaTTable.Length);
y = y / 2 - Index - 810;
Delta = (GFX.DeltaTTable[Index] + (GFX.DeltaTTable[Index + 1] - GFX.DeltaTTable[Index]) * y);
}
else if (y <= 2000)
{
int nLookupSize = GFX.DeltaTTable.Length;
Delta = GFX.DeltaTTable[nLookupSize - 1];
}
else if (y < 2100)
{
Delta = 102 + (102 * T) + (25.3 * T * T) + 0.37 * (y - 2100);
}
else
{
Delta = 102 + (102 * T) + (25.3 * T * T);
}
return(Delta);
}
