Subversion Repositories planix.SVN

#include "astro.h"

void

helio(void)

{

/*

 *	uses lambda, beta, rad, motion

 *	sets alpha, delta, rp

 */

/*

 *	helio converts from ecliptic heliocentric coordinates

 *	referred to the mean equinox of date

 *	to equatorial geocentric coordinates referred to

 *	the true equator and equinox

 */

	double xmp, ymp, zmp;

	double beta2;

/*

 *	compute geocentric distance of object and

 *	compute light-time correction (i.i. planetary aberration)

 */

	xmp = rad*cos(beta)*cos(lambda);

	ymp = rad*cos(beta)*sin(lambda);

	zmp = rad*sin(beta);

	rp = sqrt((xmp+xms)*(xmp+xms) +

		(ymp+yms)*(ymp+yms) +

		(zmp+zms)*(zmp+zms));

	lmb2 = lambda - .0057756e0*rp*motion;

	xmp = rad*cos(beta)*cos(lmb2);

	ymp = rad*cos(beta)*sin(lmb2);

	zmp = rad*sin(beta);

/*

 *	compute annual parallax from the position of the sun

 */

	xmp += xms;

	ymp += yms;

	zmp += zms;

	rp = sqrt(xmp*xmp + ymp*ymp + zmp*zmp);

/*

 *	compute annual (i.e. stellar) aberration

 *	from the orbital velocity of the earth

 *	(by an incorrect method)

 */

	xmp -= xdot*rp;

	ymp -= ydot*rp;

	zmp -= zdot*rp;

/*

 *	perform the nutation and so convert from the mean

 *	equator and equinox to the true

 */

	lmb2 = atan2(ymp, xmp);

	beta2 = atan2(zmp, sqrt(xmp*xmp+ymp*ymp));

	lmb2 += phi;

/*

 *	change to equatorial coordinates

 */

	xmp = rp*cos(lmb2)*cos(beta2);

	ymp = rp*(sin(lmb2)*cos(beta2)*cos(tobliq) - sin(tobliq)*sin(beta2));

	zmp = rp*(sin(lmb2)*cos(beta2)*sin(tobliq) + cos(tobliq)*sin(beta2));

	alpha = atan2(ymp, xmp);

	delta = atan2(zmp, sqrt(xmp*xmp+ymp*ymp));

	hp = 8.794e0*radsec/rp;

	semi /= rp;

	if(rad > 0 && rad < 2.e5)

		mag += 2.17*log(rad*rp);

}