source: Sophya/trunk/SophyaExt/XephemAstroLib/ap_as.c@ 4017

#include <string.h>
#include <math.h>

#include "astro.h"

/* convert the given apparent RA/Dec to astrometric precessed to Mjd IN PLACE.
 * we have no un-abberation etc so to find the correction: assume
 * *rap and *decp are astrometric@EOD, convert to apparent and back out
 * the difference; then precess to Mjd.
 */
void
ap_as (Now *np, double Mjd, double *rap, double *decp)
{
        double r0 = *rap, d0 = *decp;
        Obj o;
        Now n;

        /* as -> ap */
        zero_mem ((void *)&o, sizeof(o));
        o.o_type = FIXED;
        o.f_RA = (float)*rap;
        o.f_dec = (float)*decp;
        o.f_epoch = (float)mjd;
        memcpy ((void *)&n, (void *)np, sizeof(Now));
        n.n_epoch = EOD;
        obj_cir (&n, &o);
        *rap -= o.s_ra - *rap;
        *decp -= o.s_dec - *decp;

        /* then back to start for second order correction */
        o.o_type = FIXED;
        o.f_RA = (float)*rap;
        o.f_dec = (float)*decp;
        o.f_epoch = (float)mjd;
        memcpy ((void *)&n, (void *)np, sizeof(Now));
        n.n_epoch = EOD;
        obj_cir (&n, &o);
        *rap -= o.s_ra - r0;
        *decp -= o.s_dec - d0;

        radecrange (rap, decp);
        precess (mjd, Mjd, rap, decp);
        radecrange (rap, decp);
}

/* convert the given astrometric RA/Dec which are precessed to Mjd into
 * apparent @ EOD IN PLACE.
 */
void
as_ap (Now *np, double Mjd, double *rap, double *decp)
{
        Obj o;
        Now n;

        zero_mem ((void *)&o, sizeof(o));
        o.o_type = FIXED;
        o.f_RA = (float)*rap;
        o.f_dec = (float)*decp;
        o.f_epoch = (float)Mjd;
        memcpy ((void *)&n, (void *)np, sizeof(Now));
        n.n_epoch = EOD;
        obj_cir (&n, &o);
        *rap = o.s_ra;
        *decp = o.s_dec;
}

/* For RCS Only -- Do Not Edit */
static char *rcsid[2] = {(char *)rcsid, "@(#) $RCSfile: ap_as.c,v $ $Date: 2011-09-21 16:17:47 $ $Revision: 1.9 $ $Name: not supported by cvs2svn $"};