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* Approximate topocentric apparent RA,Dec of a planet
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* void palRdplan( double date, int np, double elong, double phi,
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* double * ra, double * dec, double * diam );
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* date = double (Given)
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* MJD of observation (JD-2400000.5) in TDB. For all practical
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* purposes TT can be used instead of TDB, and for many applications
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* UT will do (except for the Moon).
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* elong = double (Given)
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* Observer's east longitude (radians)
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* phi = double (Given)
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* Observer's geodetic latitude (radians)
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* ra = double * (Returned)
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* RA (topocentric apparent, radians)
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* dec = double * (Returned)
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* Dec (topocentric apparent, radians)
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* diam = double * (Returned)
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* Angular diameter (equatorial, radians)
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* Approximate topocentric apparent RA,Dec of a planet, and its
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* TIMJ: Tim Jenness (JAC, Hawaii)
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* {enter_new_authors_here}
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* - Unlike with slaRdplan, Pluto is not supported.
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* - The longitude and latitude allow correction for geocentric
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* parallax. This is a major effect for the Moon, but in the
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* context of the limited accuracy of the present routine its
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* effect on planetary positions is small (negligible for the
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* outer planets). Geocentric positions can be generated by
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* appropriate use of the routines palDmoon and iauPlan94.
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* Initial version, with some documentation from SLA/F.
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* {enter_further_changes_here}
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* Copyright (C) 2012 Science and Technology Facilities Council.
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* All Rights Reserved.
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 3 of
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* the License, or (at your option) any later version.
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* This program is distributed in the hope that it will be
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* useful, but WITHOUT ANY WARRANTY; without even the implied
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* warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
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* PURPOSE. See the GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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* {note_any_bugs_here}
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void palRdplan( double date, int np, double elong, double phi,
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double * ra, double * dec, double * diam ) {
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const double AUKM = 1.49597870e8;
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/* Equatorial radii (km) */
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const double EQRAU[] = {
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/* Local variables */
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double dx,dy,dz,r,tl;
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if (np < 0 || np > 8 ) np=0; /* Sun */
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/* Approximate local sidereal time */
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stl = palGmst( date - palDt( palEpj(date)) / 86400.0) + elong;
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/* Geocentre to Moon (mean of date) */
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/* Nutation to true of date */
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palNut( date, rmat );
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iauRxp( rmat, v, vgm );
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iauRxp( rmat, &(v[3]), &(vgm[3]) );
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/* geocentre to Moon (true of date) */
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for (i=0; i<6; i++) {
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/* Not moon: precession/nutation matrix J2000 to date */
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palPrenut( 2000.0, date, rmat );
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/* Sun to Earth-Moon Barycentre (J2000) */
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palPlanet( date, 3, v, &j );
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/* Precession and nutation to date */
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iauRxp( rmat, v, vse );
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iauRxp( rmat, &(v[3]), &(vse[3]) );
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/* Sun to geocentre (true of date) */
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for (i=0; i<6; i++) {
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vsg[i] = vse[i] - 0.012150581 * vgm[i];
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/* Geocentre to Sun */
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for (i=0; i<6; i++) {
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/* Sun to Planet (J2000) */
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palPlanet( date, np, v, &j );
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/* Precession and nutation to date */
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iauRxp( rmat, v, vsp );
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iauRxp( rmat, &(v[3]), &(vsp[3]) );
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/* Geocentre to planet */
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for (i=0; i<6; i++) {
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v[i] = vsp[i] - vsg[i];
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/* Refer to origina at the observer */
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palPvobs( phi, 0.0, stl, vgo );
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for (i=0; i<6; i++) {
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/* Geometric distance (AU) */
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r = sqrt( dx*dx + dy*dy + dz*dz );
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/* Correct position for planetary aberration */
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for (i=0; i<3; i++) {
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iauC2s( v, ra, dec );
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/* Angular diameter (radians) */
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*diam = 2.0 * asin( EQRAU[np] / (r * AUKM ) );
added
removed
palRdplan.c
