/// <summary>
/// Calculates visual magnitude of Pluto
/// </summary>
private float Pluto_Magnitude(SkyContext c)
{
double distanceFromEarth = c.Get(Pluto_DistanceFromEarth);
double distanceFromSun = c.Get(Pluto_DistanceFromSun);
return(PlutoPosition.Magnitude(distanceFromEarth, distanceFromSun));
}
/// <summary>
/// Calculates heliocentrical coordinates of Pluto for J2000 epoch
/// </summary>
private CrdsHeliocentrical Pluto_HeliocentricalJ2000(SkyContext c)
{
// final difference to stop iteration process, 1 second of time
double deltaTau = TimeSpan.FromSeconds(1).TotalDays;
// time taken by the light to reach the Earth
double tau = 0;
// previous value of tau to calculate the difference
double tau0 = 1;
// Sun rectangular coordinates, J2000.0 epoch
CrdsRectangular rSun = c.Get(Sun_RectangularJ2000);
// Heliocentrical coordinates of Pluto
CrdsHeliocentrical plutoHeliocentrial = null;
// Iterative process to find heliocentrical coordinates of planet
while (Math.Abs(tau - tau0) > deltaTau)
{
// Heliocentrical coordinates of Pluto
plutoHeliocentrial = PlutoPosition.Position(c.JulianDay - tau);
// Rectangular heliocentrical coordinates of Pluto
CrdsRectangular rPluto = new CrdsEcliptical(plutoHeliocentrial.L, plutoHeliocentrial.B, plutoHeliocentrial.R).ToRectangular(epsilonJ2000);
double x = rPluto.X + rSun.X;
double y = rPluto.Y + rSun.Y;
double z = rPluto.Z + rSun.Z;
double dist = Math.Sqrt(x * x + y * y + z * z);
tau0 = tau;
tau = PlanetPositions.LightTimeEffect(dist);
}
return(plutoHeliocentrial);
}
public void Position()
{
// Mean obliquity of the ecliptic for J2000.0 epoch
const double epsilonJ2000 = 23.4392912510;
double jd = 2448908.5;
double tau = 0;
double tau0 = 1;
int iteration = 1;
// final difference to stop iteration process, 1 second of time
double deltaTau = TimeSpan.FromSeconds(1).TotalDays;
CrdsHeliocentrical posPluto = null;
CrdsHeliocentrical hEarth = null;
while (Math.Abs(tau - tau0) > deltaTau)
{
posPluto = PlutoPosition.Position(jd - tau);
if (iteration == 1)
{
Assert.AreEqual(232.74071, posPluto.L, 1e-5);
Assert.AreEqual(14.58782, posPluto.B, 1e-5);
Assert.AreEqual(29.711111, posPluto.R, 1e-6);
}
else if (iteration == 2)
{
Assert.AreEqual(232.73949, posPluto.L, 1e-5);
Assert.AreEqual(14.58801, posPluto.B, 1e-5);
Assert.AreEqual(29.711094, posPluto.R, 1e-6);
}
// get Earth coordinates
hEarth = PlanetPositions.GetPlanetCoordinates(3, jd, highPrecision: false, epochOfDate: false);
// transform to ecliptical coordinates of the Sun
CrdsEcliptical eclSun = new CrdsEcliptical(Angle.To360(hEarth.L + 180), -hEarth.B, hEarth.R);
CrdsRectangular rSun = eclSun.ToRectangular(epsilonJ2000);
if (iteration == 1)
{
Assert.AreEqual(-0.9373959, rSun.X, 1e-6);
Assert.AreEqual(-0.3131679, rSun.Y, 1e-6);
Assert.AreEqual(-0.1357792, rSun.Z, 1e-6);
}
var rPluto = new CrdsEcliptical(posPluto.L, posPluto.B, posPluto.R).ToRectangular(epsilonJ2000);
if (iteration == 1)
{
Assert.AreEqual(-17.4079141, rPluto.X, 1e-5);
Assert.AreEqual(-23.9730804, rPluto.Y, 1e-5);
Assert.AreEqual(-2.2374228, rPluto.Z, 1e-5);
}
else if (iteration == 2)
{
Assert.AreEqual(-17.4083780, rPluto.X, 1e-5);
Assert.AreEqual(-23.9727452, rPluto.Y, 1e-5);
Assert.AreEqual(-2.2371797, rPluto.Z, 1e-5);
}
double x = rPluto.X + rSun.X;
double y = rPluto.Y + rSun.Y;
double z = rPluto.Z + rSun.Z;
double dist = Math.Sqrt(x * x + y * y + z * z);
if (iteration == 1)
{
Assert.AreEqual(30.528746, dist, 1e-5);
}
else if (iteration == 2)
{
Assert.AreEqual(30.528739, dist, 1e-5);
}
tau0 = tau;
tau = PlanetPositions.LightTimeEffect(dist);
if (iteration == 1 || iteration == 2)
{
Assert.AreEqual(0.17632, tau, 1e-5);
}
iteration++;
}
// should be only 2 iterations
Assert.AreEqual(2, iteration - 1);
// ecliptical coordinates of Pluto, J2000.0 epoch
var eclPluto = posPluto.ToRectangular(hEarth).ToEcliptical();
// geocentric astrometric equatorial coordinates of Pluto, J2000.0 epoch
var eqPluto2000 = eclPluto.ToEquatorial(epsilonJ2000);
// check coordinates with possible error with 1 arcsecond
Assert.AreEqual(new HMS("15h 31m 43.8s").ToDecimalAngle(), eqPluto2000.Alpha, 1 / 3600.0);
Assert.AreEqual(new DMS("-4* 27' 29''").ToDecimalAngle(), eqPluto2000.Delta, 1 / 3600.0);
}
/// <summary>
/// Calculates apparent semidiameter of Pluto
/// </summary>
private double Pluto_Semidiameter(SkyContext c)
{
return(PlutoPosition.Semidiameter(c.Get(Pluto_DistanceFromEarth)));
}
