sean@oddjob.UUCP (Sean Casey) (02/24/86)
Here is a program to do coordinate precessions.
Sean Casey ...oddjob!sean
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#!/bin/sh
# shar: Shell Archiver
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# precess.l
# precess.c
# This archive created: Mon Feb 24 05:35:04 1986
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.TH PRECESS local "24 Feb 1986"
.UC 4
.SH NAME
precess \- precess coordinates from one equinox to another
.SH SYNOPSIS
.B precess
[
.B final
.B equinox
]
.SH DESCRIPTION
.I Precess
precesses the standard input to the final equinox specified in either the
execution line or within the standard input. Precessed coordinates are sent
to the standard output. The calculation uses Newcomb's precession method for
the mid-equinox. This program was translated from Vax fortran.
.PP
The format for input is
.PP
OBJECT H M S +/- D M S STARTING_EQUINOX [FINAL_EQUINOX]
.PP
Note that the final equinox must be included somewhere. If it is specified
in the standard input it will be used otherwise the equinox in the command
line will be the default. Precessed data is compatible with the input. Also
note that the sign of the Declination MUST be specified ( either + or - ).
.SH BUGS
We'll see. This was stolen from the Yerkes IBM 1130 many years ago.
.SH SEE ALSO
Any of our other fine Astro programs.
.SH AUTHOR
Sean Casey (...oddjob!gizmo!sean) 2/24/86;
.PP
Yerkes Observatory, Williams Bay, WI 53191
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cat << \SHAR_EOF > precess.c
/*
This program precesses coordinates from one equinox to another.
Uses standard input and output.
usage: precess [final equinox]
input: star_name h m s +/-d m s start_equinox [final_equinox]
The final equinox must be specified upon execution or within the
standard input. You MUST include the sign of the declination.
Example:
NGC1333 03 27 36 +31 17 00 1975 1950
will precess NGC1333 to 1950.
Compile: cc -o precess precess.c -lm
Author: Sean Casey Feb 24 1986 ( Original version in Vax Fortran )
*/
#include <stdio.h>
#include <math.h>
#define RAD 206264.8062
#define RAD15 (RAD/15.0)
main (argc,argv)
int argc;
char *argv[];
{
double eqobs, equn1, equn0, a,d,rh,rm,rs,dg,dm,ds;
double deq,deq2,t1900,pm,pn,pam,pdm,am,pa,pd,ap,dp;
double atof();
int cnt, hr,min,sec;
char object[80], sign,input[80];
fprintf(stderr,"%s Ver 1.0 by S. Casey Feb 24, 1986\n",argv[0]);
if (argc == 2) {
eqobs = atof(argv[1]);
}
while (gets(input) != NULL) {
cnt=sscanf(input,"%s %lf %lf %lf %c %lf %lf %lf %lf %lf",object,&rh,&rm,&rs,&sign,&dg,&dm,&ds,&equn0,&equn1);
if (cnt == 10 || cnt == 9) { /* if this looks valid, do it */
if ((sign != '+' && sign != '-') || (cnt < 10 && argc != 2)) {
fprintf(stderr,"%s:Invalid input\n",argv[0]);
exit(1);
}
if(cnt == 9 && argc == 2)equn1=eqobs;
a = (rh*3600.0 + rm*60.0 + rs)/RAD15;
d = (dg*3600.0 + dm*60.0 + ds)/RAD;
if(sign == '-')d = -d;
/* precess to final equinox using newcomb precession */
deq = equn1-equn0;
deq2 = deq/2.0;
t1900 = equn1-deq2-1900.0;
pm=46.0850+0.000279*t1900;
pn=20.0468-0.000085*t1900;
pam=pm+pn*sin(a)*sin(d)/cos(d);
pdm=pn*cos(a);
am=a+pam*deq2/RAD;
dm=d+pdm*deq2/RAD;
pa=pm+pn*sin(am)*sin(dm)/cos(dm);
pd=pn*cos(am);
am=a+pa*deq2/RAD;
dm=d+pd*deq2/RAD;
pa=pm+pn*sin(am)*sin(dm)/cos(dm);
pd=pn*cos(am);
ap=(a*RAD15+pa*deq/15.0)/3600.0;
dp=(d*RAD+pd*deq)/3600.0;
if(ap<0.0)ap +=24.0;
sign = '+';
if(dp<0.0) {
dp = -dp;
sign = '-';
}
/* print out the data */
printf("%s",object);
hr = ap; /* do RA */
min = ap*60.0; min = min % 60;
sec = ap*360000.0; sec = sec % 6000;
printf("\t%2d %2d %5.2f",hr,min,(float)sec/100.0);
hr = dp; /* do DEC */
min = dp*60.0; min = min % 60;
sec = dp*360000.0; sec = sec % 6000;
printf(" %c%2d %2d %5.2f",sign,hr,min,(float)sec/100.0);
printf(" %6.1f\n",equn1);
}
}
exit(0);
}
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