1 cd5bae78 2004-04-21 devnull #include "astro.h"
4 cd5bae78 2004-04-21 devnull helio(void)
7 cd5bae78 2004-04-21 devnull * uses lambda, beta, rad, motion
8 cd5bae78 2004-04-21 devnull * sets alpha, delta, rp
12 cd5bae78 2004-04-21 devnull * helio converts from ecliptic heliocentric coordinates
13 cd5bae78 2004-04-21 devnull * referred to the mean equinox of date
14 cd5bae78 2004-04-21 devnull * to equatorial geocentric coordinates referred to
15 cd5bae78 2004-04-21 devnull * the true equator and equinox
18 cd5bae78 2004-04-21 devnull double xmp, ymp, zmp;
19 cd5bae78 2004-04-21 devnull double beta2;
22 cd5bae78 2004-04-21 devnull * compute geocentric distance of object and
23 cd5bae78 2004-04-21 devnull * compute light-time correction (i.i. planetary aberration)
26 cd5bae78 2004-04-21 devnull xmp = rad*cos(beta)*cos(lambda);
27 cd5bae78 2004-04-21 devnull ymp = rad*cos(beta)*sin(lambda);
28 cd5bae78 2004-04-21 devnull zmp = rad*sin(beta);
29 cd5bae78 2004-04-21 devnull rp = sqrt((xmp+xms)*(xmp+xms) +
30 cd5bae78 2004-04-21 devnull (ymp+yms)*(ymp+yms) +
31 cd5bae78 2004-04-21 devnull (zmp+zms)*(zmp+zms));
32 cd5bae78 2004-04-21 devnull lmb2 = lambda - .0057756e0*rp*motion;
34 cd5bae78 2004-04-21 devnull xmp = rad*cos(beta)*cos(lmb2);
35 cd5bae78 2004-04-21 devnull ymp = rad*cos(beta)*sin(lmb2);
36 cd5bae78 2004-04-21 devnull zmp = rad*sin(beta);
39 cd5bae78 2004-04-21 devnull * compute annual parallax from the position of the sun
42 cd5bae78 2004-04-21 devnull xmp += xms;
43 cd5bae78 2004-04-21 devnull ymp += yms;
44 cd5bae78 2004-04-21 devnull zmp += zms;
45 cd5bae78 2004-04-21 devnull rp = sqrt(xmp*xmp + ymp*ymp + zmp*zmp);
48 cd5bae78 2004-04-21 devnull * compute annual (i.e. stellar) aberration
49 cd5bae78 2004-04-21 devnull * from the orbital velocity of the earth
50 cd5bae78 2004-04-21 devnull * (by an incorrect method)
53 cd5bae78 2004-04-21 devnull xmp -= xdot*rp;
54 cd5bae78 2004-04-21 devnull ymp -= ydot*rp;
55 cd5bae78 2004-04-21 devnull zmp -= zdot*rp;
58 cd5bae78 2004-04-21 devnull * perform the nutation and so convert from the mean
59 cd5bae78 2004-04-21 devnull * equator and equinox to the true
62 cd5bae78 2004-04-21 devnull lmb2 = atan2(ymp, xmp);
63 cd5bae78 2004-04-21 devnull beta2 = atan2(zmp, sqrt(xmp*xmp+ymp*ymp));
64 cd5bae78 2004-04-21 devnull lmb2 += phi;
67 cd5bae78 2004-04-21 devnull * change to equatorial coordinates
70 cd5bae78 2004-04-21 devnull xmp = rp*cos(lmb2)*cos(beta2);
71 cd5bae78 2004-04-21 devnull ymp = rp*(sin(lmb2)*cos(beta2)*cos(tobliq) - sin(tobliq)*sin(beta2));
72 cd5bae78 2004-04-21 devnull zmp = rp*(sin(lmb2)*cos(beta2)*sin(tobliq) + cos(tobliq)*sin(beta2));
74 cd5bae78 2004-04-21 devnull alpha = atan2(ymp, xmp);
75 cd5bae78 2004-04-21 devnull delta = atan2(zmp, sqrt(xmp*xmp+ymp*ymp));
77 cd5bae78 2004-04-21 devnull hp = 8.794e0*radsec/rp;
78 cd5bae78 2004-04-21 devnull semi /= rp;
79 cd5bae78 2004-04-21 devnull if(rad > 0 && rad < 2.e5)
80 cd5bae78 2004-04-21 devnull mag += 2.17*log(rad*rp);