/// <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); }