public static Apogee GetApogeeEvents(DateTime d)
{
//Iterate in 5 month increments due to formula variations.
//Determine closest events to date.
//apo1 is last date
//apo2 is next date
//integrity for new date.
if (d.Year <= 0001)
{
return(new Apogee(new PerigeeApogee(new DateTime(), 0, new Distance(0)), new PerigeeApogee(new DateTime(), 0, new Distance(0))));
}
PerigeeApogee apo1 = MoonPerigeeOrApogee(d.AddDays(-45), MoonDistanceType.Apogee);
PerigeeApogee apo2 = MoonPerigeeOrApogee(d.AddDays(-45), MoonDistanceType.Apogee);
for (int x = -30; x <= 45; x += 15)
{
PerigeeApogee t = MoonPerigeeOrApogee(d.AddDays(x), MoonDistanceType.Apogee);
//Find next apogee after specified date
if (t.Date > apo2.Date && t.Date >= d)
{
apo2 = t;
break;
}
//Find last apogee before specified date
if (t.Date > apo1.Date && t.Date < d)
{
apo1 = t;
apo2 = t;
}
}
return(new Apogee(apo1, apo2));
}
private PerigeeApogee Get_Correct_Slipped_Date(PerigeeApogee actual, PerigeeApogee pre, PerigeeApogee post, int i)
{
switch (i)
{
case 0:
return(pre);
case 1:
return(actual);
case 2:
return(post);
default:
return(actual);
}
}
public static Perigee GetPerigeeEvents(DateTime d)
{
//Iterate in 15 day increments due to formula variations.
//Determine closest events to date.
//per1 is last date
//per2 is next date
//integrity for new date.
if (d.Year <= 0001)
{
return(new Perigee(new PerigeeApogee(new DateTime(), 0, new Distance(0)), new PerigeeApogee(new DateTime(), 0, new Distance(0))));
}
//Start at lowest increment
PerigeeApogee per1 = MoonPerigeeOrApogee(d.AddDays(-45), MoonDistanceType.Perigee);
PerigeeApogee per2 = MoonPerigeeOrApogee(d.AddDays(-45), MoonDistanceType.Perigee);
for (int x = -30; x <= 45; x += 15)
{
//used for comparison
PerigeeApogee t = MoonPerigeeOrApogee(d.AddDays(x), MoonDistanceType.Perigee);
//Find the next pergiee after specified date
if (t.Date > per2.Date && t.Date >= d)
{
per2 = t;
break;
}
//Find last perigee before specified date
if (t.Date > per1.Date && t.Date < d)
{
per1 = t;
per2 = t;
}
}
return(new Perigee(per1, per2));
}
//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);
}
/// <summary>
/// Initializes an Apogee object.
/// </summary>
/// <param name="last"></param>
/// <param name="next"></param>
public Apogee(PerigeeApogee last, PerigeeApogee next)
{
lastApogee = last;
nextApogee = next;
}
