/*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library 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
* Lesser 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* Some functions in this file use the VSOP87 solution by
* Messrs. Bretagnon and Francou.
*
* Copyright (C) 2000 - 2005 Liam Girdwood
*/
#include <math.h>
#include <libnova/vsop87.h>
#include <libnova/utility.h>
double ln_calc_series (const struct ln_vsop * data, int terms, double t)
{
double value = 0;
int i;
for (i=0; i<terms; i++) {
value += data->A * cos(data->B + data->C * t);
data++;
}
return value;
}
/*! \fn void ln_vsop87_to_fk5 (struct ln_helio_posn * position, double JD)
* \param position Position to transform.
* \param JD Julian day
*
* Transform from VSOP87 to FK5 reference frame.
*/
/* Equation 31.3 Pg 207.
*/
void ln_vsop87_to_fk5 (struct ln_helio_posn * position, double JD)
{
double LL, cos_LL, sin_LL, T, delta_L, delta_B, B;
/* get julian centuries from 2000 */
T = (JD - 2451545.0)/ 36525.0;
LL = position->L + ( - 1.397 - 0.00031 * T ) * T;
LL = ln_deg_to_rad (LL);
cos_LL = cos(LL);
sin_LL = sin(LL);
B = ln_deg_to_rad(position->B);
delta_L = (-0.09033 / 3600.0) + (0.03916 / 3600.0) * (cos_LL + sin_LL) * tan (B);
delta_B = (0.03916 / 3600.0) * (cos_LL - sin_LL);
position->L += delta_L;
position->B += delta_B;
}