mirror of https://github.com/XEphem/XEphem.git
70 lines
1.7 KiB
C
70 lines
1.7 KiB
C
#include <stdio.h>
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#include <math.h>
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#include "astro.h"
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static void m (double t, double k, double *mj);
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#define unw(w,z) ((w)-floor((w)/(z))*(z))
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/* given a modified Julian date, mj, return the mjd of the new
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* and full moons about then, mjn and mjf.
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* TODO: exactly which ones does it find? eg:
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* 5/28/1988 yields 5/15 and 5/31
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* 5/29 6/14 6/29
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*/
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void
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moonnf (double mj, double *mjn, double *mjf)
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{
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int mo, yr;
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double dy;
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double mj0;
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double k, tn, tf, t;
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mjd_cal (mj, &mo, &dy, &yr);
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cal_mjd (1, 0., yr, &mj0);
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k = (yr-1900+((mj-mj0)/365))*12.3685;
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k = floor(k+0.5);
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tn = k/1236.85;
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tf = (k+0.5)/1236.85;
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t = tn;
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m (t, k, mjn);
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t = tf;
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k += 0.5;
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m (t, k, mjf);
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}
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static void
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m (double t, double k, double *mj)
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{
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double t2, a, a1, b, b1, c, ms, mm, f, ddjd;
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t2 = t*t;
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a = 29.53*k;
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c = degrad(166.56+(132.87-9.173e-3*t)*t);
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b = 5.8868e-4*k+(1.178e-4-1.55e-7*t)*t2+3.3e-4*sin(c)+7.5933E-1;
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ms = 359.2242+360*unw(k/1.236886e1,1)-(3.33e-5+3.47e-6*t)*t2;
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mm = 306.0253+360*unw(k/9.330851e-1,1)+(1.07306e-2+1.236e-5*t)*t2;
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f = 21.2964+360*unw(k/9.214926e-1,1)-(1.6528e-3+2.39e-6*t)*t2;
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ms = unw(ms,360);
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mm = unw(mm,360);
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f = unw(f,360);
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ms = degrad(ms);
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mm = degrad(mm);
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f = degrad(f);
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ddjd = (1.734e-1-3.93e-4*t)*sin(ms)+2.1e-3*sin(2*ms)
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-4.068e-1*sin(mm)+1.61e-2*sin(2*mm)-4e-4*sin(3*mm)
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+1.04e-2*sin(2*f)-5.1e-3*sin(ms+mm)-7.4e-3*sin(ms-mm)
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+4e-4*sin(2*f+ms)-4e-4*sin(2*f-ms)-6e-4*sin(2*f+mm)
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+1e-3*sin(2*f-mm)+5e-4*sin(ms+2*mm);
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a1 = (long)a;
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b = b+ddjd+(a-a1);
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b1 = (long)b;
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a = a1+b1;
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b = b-b1;
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*mj = a + b;
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}
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/* For RCS Only -- Do Not Edit */
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static char *rcsid[2] = {(char *)rcsid, "@(#) $RCSfile: moonnf.c,v $ $Date: 2003/03/20 08:50:15 $ $Revision: 1.1 $ $Name: $"};
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