This is nutation.c in view mode; [Download] [Up]
#include <stdio.h>
#include <math.h>
#include "astro.h"
/* given the modified JD, mjd, find the nutation in obliquity, *deps, and
* the nutation in longitude, *dpsi, each in radians.
*/
nutation (mjd, deps, dpsi)
double mjd;
double *deps, *dpsi;
{
static double lastmjd = -10000, lastdeps, lastdpsi;
double ls, ld; /* sun's mean longitude, moon's mean longitude */
double ms, md; /* sun's mean anomaly, moon's mean anomaly */
double nm; /* longitude of moon's ascending node */
double t, t2; /* number of Julian centuries of 36525 days since
* Jan 0.5 1900.
*/
double tls, tnm, tld; /* twice above */
double a, b; /* temps */
if (mjd == lastmjd) {
*deps = lastdeps;
*dpsi = lastdpsi;
return;
}
t = mjd/36525.;
t2 = t*t;
a = 100.0021358*t;
b = 360.*(a-(long)a);
ls = 279.697+.000303*t2+b;
a = 1336.855231*t;
b = 360.*(a-(long)a);
ld = 270.434-.001133*t2+b;
a = 99.99736056000026*t;
b = 360.*(a-(long)a);
ms = 358.476-.00015*t2+b;
a = 13255523.59*t;
b = 360.*(a-(long)a);
md = 296.105+.009192*t2+b;
a = 5.372616667*t;
b = 360.*(a-(long)a);
nm = 259.183+.002078*t2-b;
/* convert to radian forms for use with trig functions.
*/
tls = 2*degrad(ls);
nm = degrad(nm);
tnm = 2*nm;
ms = degrad(ms);
tld = 2*degrad(ld);
md = degrad(md);
/* find delta psi and eps, in arcseconds.
*/
lastdpsi = (-17.2327-.01737*t)*sin(nm)+(-1.2729-.00013*t)*sin(tls)
+.2088*sin(tnm)-.2037*sin(tld)+(.1261-.00031*t)*sin(ms)
+.0675*sin(md)-(.0497-.00012*t)*sin(tls+ms)
-.0342*sin(tld-nm)-.0261*sin(tld+md)+.0214*sin(tls-ms)
-.0149*sin(tls-tld+md)+.0124*sin(tls-nm)+.0114*sin(tld-md);
lastdeps = (9.21+.00091*t)*cos(nm)+(.5522-.00029*t)*cos(tls)
-.0904*cos(tnm)+.0884*cos(tld)+.0216*cos(tls+ms)
+.0183*cos(tld-nm)+.0113*cos(tld+md)-.0093*cos(tls-ms)
-.0066*cos(tls-nm);
/* convert to radians.
*/
lastdpsi = degrad(lastdpsi/3600);
lastdeps = degrad(lastdeps/3600);
lastmjd = mjd;
*deps = lastdeps;
*dpsi = lastdpsi;
}
These are the contents of the former NiCE NeXT User Group NeXTSTEP/OpenStep software archive, currently hosted by Netfuture.ch.