mirror of https://github.com/XEphem/XEphem.git
67 lines
1.5 KiB
C
67 lines
1.5 KiB
C
#include <string.h>
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#include <math.h>
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#include "astro.h"
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/* convert the given apparent RA/Dec to astrometric precessed to Mjd IN PLACE.
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* we have no un-abberation etc so to find the correction: assume
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* *rap and *decp are astrometric@EOD, convert to apparent and back out
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* the difference; then precess to Mjd.
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*/
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void
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ap_as (Now *np, double Mjd, double *rap, double *decp)
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{
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double r0 = *rap, d0 = *decp;
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Obj o;
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Now n;
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/* as -> ap */
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zero_mem ((void *)&o, sizeof(o));
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o.o_type = FIXED;
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o.f_RA = (float)*rap;
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o.f_dec = (float)*decp;
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o.f_epoch = (float)mjd;
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memcpy ((void *)&n, (void *)np, sizeof(Now));
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n.n_epoch = EOD;
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obj_cir (&n, &o);
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*rap -= o.s_ra - *rap;
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*decp -= o.s_dec - *decp;
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/* then back to start for second order correction */
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o.o_type = FIXED;
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o.f_RA = (float)*rap;
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o.f_dec = (float)*decp;
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o.f_epoch = (float)mjd;
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memcpy ((void *)&n, (void *)np, sizeof(Now));
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n.n_epoch = EOD;
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obj_cir (&n, &o);
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*rap -= o.s_ra - r0;
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*decp -= o.s_dec - d0;
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radecrange (rap, decp);
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precess (mjd, Mjd, rap, decp);
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radecrange (rap, decp);
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}
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/* convert the given astrometric RA/Dec which are precessed to Mjd into
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* apparent @ EOD IN PLACE.
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*/
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void
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as_ap (Now *np, double Mjd, double *rap, double *decp)
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{
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Obj o;
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Now n;
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zero_mem ((void *)&o, sizeof(o));
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o.o_type = FIXED;
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o.f_RA = (float)*rap;
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o.f_dec = (float)*decp;
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o.f_epoch = (float)Mjd;
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memcpy ((void *)&n, (void *)np, sizeof(Now));
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n.n_epoch = EOD;
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obj_cir (&n, &o);
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*rap = o.s_ra;
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*decp = o.s_dec;
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}
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