public void ToTopocentric()
{
// Geocentric coordinates of Mars
CrdsEquatorial eq = new CrdsEquatorial(339.530208, -15.771083);
// Palomar Observatory coordinates, see example 11.a
CrdsGeographical geo = new CrdsGeographical(new HMS("7h 47m 27s").ToDecimalAngle(), new DMS("+33* 21' 22''").ToDecimalAngle(), 1706);
// Equatoria horizontal parallax
double pi = 23.592 / 3600;
// Apparent sidereal time at Greenwich
double theta0 = new HMS("1h 40m 45s").ToDecimalAngle();
// Equatorial topocentric coordinates of Mars
CrdsEquatorial topo = eq.ToTopocentric(geo, theta0, pi);
Assert.AreEqual(new HMS("22h 38m 08.54s").ToDecimalAngle(), topo.Alpha, errorInHMS);
Assert.AreEqual(new DMS("-15* 46' 30.04''").ToDecimalAngle(), topo.Delta, errorInDMS);
}
private void DoTest(CrdsGeographical location, OrbitalElements oe, string testData, double errorR, double errorEq)
{
Regex regex = new Regex("^(\\S+)\\s+(\\S+)\\s+(\\S+)\\s+(\\S+)\\s+(\\S+ \\S+ \\S+) (\\S+ \\S+ \\S+)$");
string[] lines = testData.Split('\n');
foreach (string line in lines)
{
string dataLine = line.Trim();
if (!string.IsNullOrEmpty(dataLine))
{
var match = regex.Match(dataLine);
double jd = double.Parse(match.Groups[1].Value, CultureInfo.InvariantCulture);
double X = double.Parse(match.Groups[2].Value, CultureInfo.InvariantCulture);
double Y = double.Parse(match.Groups[3].Value, CultureInfo.InvariantCulture);
double Z = double.Parse(match.Groups[4].Value, CultureInfo.InvariantCulture);
string ra = match.Groups[5].Value;
string dec = match.Groups[6].Value;
var eqTest = new CrdsEquatorial(new HMS(ra), new DMS(dec));
var nutation = Nutation.NutationElements(jd);
var aberration = Aberration.AberrationElements(jd);
// True obliquity
double epsilon = Date.TrueObliquity(jd, nutation.deltaEpsilon);
// 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;
// Rectangular coordinates of minor body
CrdsRectangular r = null;
// Rectangular coordinates of the Sun
var sun = SunRectangular(jd, epsilon);
// Distance to the Earth
double Delta = 0;
// Iterative process to find rectangular coordinates of minor body
while (Math.Abs(tau - tau0) > deltaTau)
{
// Rectangular coordinates of minor body
r = MinorBodyPositions.GetRectangularCoordinates(oe, jd - tau, epsilon);
double ksi = sun.X + r.X;
double eta = sun.Y + r.Y;
double zeta = sun.Z + r.Z;
// Distance to the Earth
Delta = Math.Sqrt(ksi * ksi + eta * eta + zeta * zeta);
tau0 = tau;
tau = PlanetPositions.LightTimeEffect(Delta);
}
// Test heliocentric rectangular coordinates
Assert.AreEqual(X, r.X, errorR);
Assert.AreEqual(Y, r.Y, errorR);
Assert.AreEqual(Z, r.Z, errorR);
double x = sun.X + r.X;
double y = sun.Y + r.Y;
double z = sun.Z + r.Z;
double alpha = Angle.ToDegrees(Math.Atan2(y, x));
double delta = Angle.ToDegrees(Math.Asin(z / Delta));
var eq0 = new CrdsEquatorial(alpha, delta);
var theta0 = Date.ApparentSiderealTime(jd, nutation.deltaPsi, epsilon);
var parallax = PlanetEphem.Parallax(Delta);
var eq = eq0.ToTopocentric(location, theta0, parallax);
// Test equatorial coordinates
Assert.AreEqual(eqTest.Alpha, eq.Alpha, errorEq / 3600.0);
Assert.AreEqual(eqTest.Delta, eq.Delta, errorEq / 3600.0);
}
}
}
