public GCEquatorialCoords getTopocentricEquatorial(GCEarthData obs, double jdate)
{
double u, h, delta_alpha;
double rho_sin, rho_cos;
const double b_a = 0.99664719;
GCEquatorialCoords tec = new GCEquatorialCoords();
double altitude = 0;
// geocentric position of observer on the earth surface
// 10.1 - 10.3
u = GCMath.arcTanDeg(b_a * b_a * GCMath.tanDeg(obs.latitudeDeg));
rho_sin = b_a * GCMath.sinDeg(u) + altitude / 6378140.0 * GCMath.sinDeg(obs.latitudeDeg);
rho_cos = GCMath.cosDeg(u) + altitude / 6378140.0 * GCMath.cosDeg(obs.latitudeDeg);
// equatorial horizontal paralax
// 39.1
double parallax = GCMath.arcSinDeg(GCMath.sinDeg(8.794 / 3600) / (radius / GCMath.AU));
// geocentric hour angle of the body
h = GCEarthData.SiderealTimeGreenwich(jdate) + obs.longitudeDeg - rightAscension;
// 39.2
delta_alpha = GCMath.arcTanDeg(
(-rho_cos * GCMath.sinDeg(parallax) * GCMath.sinDeg(h)) /
(GCMath.cosDeg(this.declination) - rho_cos * GCMath.sinDeg(parallax) * GCMath.cosDeg(h)));
tec.rightAscension = rightAscension + delta_alpha;
tec.declination = declination + GCMath.arcTanDeg(
((GCMath.sinDeg(declination) - rho_sin * GCMath.sinDeg(parallax)) * GCMath.cosDeg(delta_alpha)) /
(GCMath.cosDeg(declination) - rho_cos * GCMath.sinDeg(parallax) * GCMath.cosDeg(h)));
return(tec);
}
public void CorrectEqatorialWithParallax(double jdate, double latitude, double longitude, double height)
{
double u, hourAngleBody, delta_alpha;
double rho_sin, rho_cos;
const double b_a = 0.99664719;
// calculate geocentric longitude and latitude of observer
u = GCMath.arcTanDeg(b_a * b_a * GCMath.tanDeg(latitude));
rho_sin = b_a * GCMath.sinDeg(u) + height / 6378140.0 * GCMath.sinDeg(latitude);
rho_cos = GCMath.cosDeg(u) + height / 6378140.0 * GCMath.cosDeg(latitude);
// calculate paralax
this.parallax = GCMath.arcSinDeg(GCMath.sinDeg(8.794 / 3600) / (MoonDistance(jdate) / GCMath.AU));
// calculate correction of equatorial coordinates
hourAngleBody = GCEarthData.SiderealTimeGreenwich(jdate) + longitude - this.rightAscension;
delta_alpha = GCMath.arcTan2Deg(-rho_cos * GCMath.sinDeg(this.parallax) * GCMath.sinDeg(hourAngleBody),
GCMath.cosDeg(this.declination) - rho_cos * GCMath.sinDeg(this.parallax) * GCMath.cosDeg(hourAngleBody));
this.rightAscension += delta_alpha;
this.declination += GCMath.arcTan2Deg(
(GCMath.sinDeg(this.declination) - rho_sin * GCMath.sinDeg(this.parallax)) * GCMath.cosDeg(delta_alpha),
GCMath.cosDeg(this.declination) - rho_cos * GCMath.sinDeg(this.parallax) * GCMath.cosDeg(hourAngleBody));
}
