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/*****************************************************************************/
/* easpec.c */
/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
/* Calculates Earth-specific quantities (inclination of the rotation axis, */
/* sideral time, geocentric position of an observer, ...) */
/* This part of the library is not standalone (depends on earth and cmath). */
/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
/* (c) 2003, 2006; Pal, A. (apal@szofi.elte.hu). */
/*****************************************************************************/
#include <stdio.h>
#include <math.h>
#include <astro/astro.h>
#include <astro/earth.h>
#include <astro/easpec.h>
/*****************************************************************************/
#ifndef M_PI
#define M_PI 3.1415926535897932384626433832795028841968
#endif
/*****************************************************************************/
double get_earth_axis_angle(double jdate)
{
double jc;
static double cjdate=0.0,ce=0.0;
if ( cjdate==jdate ) return(ce);
jc=(jdate-2451545.0)/36525.0;
ce=23.439291+(-0.0130042+(-0.00000016+0.000000504*jc)*jc)*jc;
cjdate=jdate;
return(ce);
}
double get_sideral_time(double jdate)
{
double jc,jday;
static double cjdate=0.0,csid=0.0;
if ( cjdate==jdate ) return(csid);
jday=(double)((long)(jdate-0.5))+0.5;
jc=(jday-2415020.0)/36525.0;
csid=0.276919398+(100.0021359+0.000001075*jc)*jc;
csid+=1.002737908*(jdate-jday);
if ( csid<0 ) csid+=(double)((long)(-csid))+10.0;
csid=csid-(double)((long)csid);
csid=csid*360.0;
cjdate=jdate;
return(csid);
}
void get_observer_coords(double jdate,double lon,double lat,double *x,double *y,double *z)
{
double wx,wy,n,d,lst;
lst=get_sideral_time(jdate)+lon;
wx=r_earth_equ*cosa(lat);
wy=r_earth_pol*sina(lat);
n=sqrt(wx*wx+wy*wy);
d =r_earth_equ*wx/n;
*z=r_earth_pol*wy/n;
*x=d*cosa(lst);
*y=d*sina(lst);
}
double get_heliocentric_julian_date_diff(double jd,double ra,double dec)
{
double rx,ry,rz;
double nx,ny,nz;
double eps,dis,hjd_diff;
get_earth_coords(jd,&rx,&ry,&rz);
eps=get_earth_axis_angle(jd);
nx=cosa(dec)*cosa(ra);
ny=cosa(dec)*sina(ra);
nz=sina(dec);
rotate(&ny,&nz,-eps);
/* jd0=get_julian_date(2000,1,1); */
/* rotate(&nx,&ny,(jd-jd0)/(365.25*25800.0)*360.0); */
dis=nx*rx+ny*ry+nz*rz;
hjd_diff=dis * 0.0057755178;
return(hjd_diff);
}
double get_heliocentric_julian_date(double jd,double ra,double dec)
{
double hjd;
hjd=jd + get_heliocentric_julian_date_diff(jd,ra,dec);
return(hjd);
}
double get_heliocentric_julian_date_epoch(double jd,double ra,double dec,double y0)
{
double rx,ry,rz;
double nx,ny,nz;
double eps,dis,hjd,jd0;
get_earth_coords(jd,&rx,&ry,&rz);
eps=get_earth_axis_angle(jd);
nx=cosa(dec)*cosa(ra);
ny=cosa(dec)*sina(ra);
nz=sina(dec);
rotate(&ny,&nz,-eps);
jd0=2451545.0+(y0-2000.0)*365.25;
rotate(&nx,&ny,(jd-jd0)/(365.25*25800.0)*360.0);
dis=nx*rx+ny*ry+nz*rz;
hjd=jd + dis * 0.0057755178;
return(hjd);
}
double get_barycentric_julian_date_diff(double jd,double ra,double dec)
{
double rx,ry,rz;
double nx,ny,nz;
double bx,by,bz,tmass;
double jupx,jupy,jupz,
satx,saty,satz,
urax,uray,uraz,
nepx,nepy,nepz;
double eps,dis,bjd_diff;
get_planet_coords(jd,5,&jupx,&jupy,&jupz);
get_planet_coords(jd,6,&satx,&saty,&satz);
get_planet_coords(jd,7,&urax,&uray,&uraz);
get_planet_coords(jd,8,&nepx,&nepy,&nepz);
tmass=1+m_jupiter+m_saturn+m_uranus+m_neptune;
bx=(jupx*m_jupiter+satx*m_saturn+urax*m_uranus+nepx*m_neptune)/tmass;
by=(jupy*m_jupiter+saty*m_saturn+uray*m_uranus+nepy*m_neptune)/tmass;
bz=(jupz*m_jupiter+satz*m_saturn+uraz*m_uranus+nepz*m_neptune)/tmass;
get_earth_coords(jd,&rx,&ry,&rz);
rx-=bx;
ry-=by;
rz-=bz;
eps=get_earth_axis_angle(jd);
nx=cosa(dec)*cosa(ra);
ny=cosa(dec)*sina(ra);
nz=sina(dec);
rotate(&ny,&nz,-eps);
/* jd0=get_julian_date(2000,1,1); */
/* rotate(&nx,&ny,(jd-jd0)/(365.25*25800.0)*360.0); */
dis=nx*rx+ny*ry+nz*rz;
bjd_diff=dis * 0.0057755178;
return(bjd_diff);
}
double get_barycentric_julian_date(double jd,double ra,double dec)
{
double bjd;
bjd=jd + get_barycentric_julian_date_diff(jd,ra,dec);
return(bjd);
}
int get_annular_parallax_correction(double jd,double ra,double dec,double dis,double *rra,double *rdec)
{
double x0,y0,z0,dx,dy,dz,eps;
x0=dis*cosa(dec)*cosa(ra);
y0=dis*cosa(dec)*sina(ra);
z0=dis*sina(dec);
get_earth_coords(jd,&dx,&dy,&dz);
eps=get_earth_axis_angle(jd);
rotate(&dy,&dz,+eps);
x0+=dx*M_PI/(180.0*3600.0);
y0+=dy*M_PI/(180.0*3600.0);
z0+=dz*M_PI/(180.0*3600.0);
*rra=getpcoords(x0,y0);
dis=sqrt(x0*x0+y0*y0+z0*z0);
*rdec=asina(z0/dis);
return(0);
}
/*****************************************************************************/
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