/*
*+
* Name:
* palSubet
* Purpose:
* Remove the E-terms from a pre IAU 1976 catalogue RA,Dec
* Language:
* Starlink ANSI C
* Type of Module:
* Library routine
* Invocation:
* void palSubet ( double rc, double dc, double eq,
* double *rm, double *dm );
* Arguments:
* rc = double (Given)
* RA with E-terms included (radians)
* dc = double (Given)
* Dec with E-terms included (radians)
* eq = double (Given)
* Besselian epoch of mean equator and equinox
* rm = double * (Returned)
* RA without E-terms (radians)
* dm = double * (Returned)
* Dec without E-terms (radians)
* Description:
* Remove the E-terms (elliptic component of annual aberration)
* from a pre IAU 1976 catalogue RA,Dec to give a mean place.
* Authors:
* PTW: Pat Wallace (STFC)
* TIMJ: Tim Jenness (JAC, Hawaii)
* {enter_new_authors_here}
* Notes:
* Most star positions from pre-1984 optical catalogues (or
* derived from astrometry using such stars) embody the
* E-terms. This routine converts such a position to a
* formal mean place (allowing, for example, comparison with a
* pulsar timing position).
* See Also:
* Explanatory Supplement to the Astronomical Ephemeris,
* section 2D, page 48.
* History:
* 2012-02-12(TIMJ):
* Initial version with documentation taken from Fortran SLA
* {enter_further_changes_here}
* Copyright:
* Copyright (C) 2012 Science and Technology Facilities Council.
* All Rights Reserved.
* Licence:
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 3 of
* the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be
* useful, but WITHOUT ANY WARRANTY; without even the implied
* warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
* PURPOSE. See the GNU General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301
* USA.
* Bugs:
* {note_any_bugs_here}
*-
*/
#include "pal.h"
#include "sofa.h"
void palSubet ( double rc, double dc, double eq, double *rm, double *dm ) {
double a[3]; /* The E-terms */
double v[3];
double f;
int i;
/* Note the preference for IAU routines */
/* Retrieve the E-terms */
palEtrms( eq, a );
/* Spherical to Cartesian */
iauS2c( rc, dc, v );
/* Include the E-terms */
f = 1.0 + iauPdp( v, a );
for (i=0; i<3; i++) {
v[i] = f*v[i] - a[i];
}
/* Cartesian to spherical */
iauC2s( v, rm, dm );
/* Bring RA into conventional range */
*rm = iauAnp( *rm );
}