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Added correction for motion of stars during exposure (pretty major bug)

pull/13/merge
Cees Bassa 2018-02-27 09:53:30 +01:00
parent 35281d2c50
commit 082f9b5155
1 changed files with 35 additions and 7 deletions
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42
reduce.c
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@ -58,7 +58,8 @@ void mjd2date(double mjd,char *date);
void dec2sex(double x,char *s,int type);
float linear_fit(float x[],float y[],int n,float a[],float sa[]);
int fgetline(FILE *file,char *s,int lim);
double gmst(double mjd);
double modulo(double x,double y);
// Find peak
float find_peak(float *z,int kx,int ky,int xmin,int xmax,int ymin,int ymax,float s,int mx,int my,float *x0,float *y0)
@ -213,7 +214,7 @@ void reduce_point(struct observation *obs,struct image img,float tmid,float x,fl
int i,iframe,k;
double ra,de,rx,ry;
float dx,dy,dt;
double mjd;
double mjd,mjd1,dra;
char nfd[32],sra[15],sde[15];
float ax[2],ay[2];
@ -224,11 +225,6 @@ void reduce_point(struct observation *obs,struct image img,float tmid,float x,fl
ry=img.b[0]+img.b[1]*dx+img.b[2]*dy;
reverse(img.ra0,img.de0,rx,ry,&ra,&de);
dec2sex(ra/15.0,sra,0);
dec2sex(de,sde,1);
obs->ra=ra;
obs->de=de;
// Transform direction
for (i=0;i<2;i++) {
ax[i]=obs->ax[i];
@ -247,6 +243,17 @@ void reduce_point(struct observation *obs,struct image img,float tmid,float x,fl
mjd=nfd2mjd(img.nfd)+(double) dt/86400.0;
mjd2date(mjd,nfd);
obs->mjd=mjd;
// Correct for motion
mjd1=img.mjd+0.5*(double) img.exptime/86400.0;
dra=gmst(mjd)-gmst(mjd1);
ra+=dra;
// Get RA/Dec
dec2sex(ra/15.0,sra,0);
dec2sex(de,sde,1);
obs->ra=ra;
obs->de=de;
// Copy
strcpy(obs->nfd,nfd);
@ -1485,3 +1492,24 @@ int fgetline(FILE *file,char *s,int lim)
s[i] = '\0';
return i;
}
// Return x modulo y [0,y)
double modulo(double x,double y)
{
x=fmod(x,y);
if (x<0.0) x+=y;
return x;
}
// Greenwich Mean Sidereal Time
double gmst(double mjd)
{
double t,gmst;
t=(mjd-51544.5)/36525.0;
gmst=modulo(280.46061837+360.98564736629*(mjd-51544.5)+t*t*(0.000387933-t/38710000),360.0);
return gmst;
}