int writeMoon (double jd, struct ln_lnlat_posn obs) {
struct ln_equ_posn equ; // equatorial moon position
struct ln_hrz_posn hrz; // horiz alt/az
double lum; // luminance, best guess
double discSize; // solar disc size from libnova
double adjAlt; // altitude adjustment
float lunPos[3],lunC[3];
double phase,discFrac,limb;
// set lunar color (slightly brownish)
lunC[0] = 1.05;
lunC[1] = 1.00;
lunC[2] = 0.85;
// should really modify this near the horizon!
// get moon position
ln_get_lunar_equ_coords (jd, &equ);
ln_get_hrz_from_equ (&equ, &obs, jd, &hrz);
// 360 deg azimuth is due South, 270 is due East
// position in vector format
lunPos[0] = -sin(hrz.az*DEGTORAD)*cos(hrz.alt*DEGTORAD);
lunPos[1] = -cos(hrz.az*DEGTORAD)*cos(hrz.alt*DEGTORAD);
lunPos[2] = sin(hrz.alt*DEGTORAD);
fprintf(stdout,"\n# Lunar altitude %7.3f deg, azimuth %7.3f deg\n",hrz.alt,hrz.az);
if (hrz.alt < -5.0) {
return(FALSE);
}
// get phase and fraction illuminated
phase = ln_get_lunar_phase(jd);
discFrac = ln_get_lunar_disk(jd);
// get disc size
discSize = 2.*ln_get_lunar_sdiam(jd)/3600.0;
fprintf(stdout,"# lunar phase %7.3f, disc illum fraction %7.3f, disc size %6.2f deg\n",phase,discFrac,discSize);
// phase 0/360 is full, 180 is new
// get phase details -- later
// limb = ln_get_lunar_bright_limb(jd);
// get altitude adjustment due to refraction (altitude, p in millibars, temp in C)
adjAlt = ln_get_refraction_adj (hrz.alt,1010.,10.);
// luminance is 1/449000 of full bright sun
// and scaled by fraction visible
lum = 15.6 * pow(discFrac,2);
// moon is a source, like the sun
fprintf(stdout,"void light lunar\n");
fprintf(stdout,"0\n0\n3 %g %g %g\n",lum*lunC[0],lum*lunC[1],lum*lunC[2]);
// complete the moon
fprintf(stdout,"lunar source moon\n");
fprintf(stdout,"0\n0\n4 %g %g %g %.3f\n",lunPos[0],lunPos[1],lunPos[2],discSize);
return(TRUE);
}
int main (int argc, char* argv[])
{
double JD;
struct ln_rect_posn moon;
struct ln_equ_posn equ;
struct ln_lnlat_posn ecl;
struct ln_lnlat_posn observer;
struct ln_rst_time rst;
struct ln_zonedate rise, transit, set;
/* observers location (Edinburgh), used to calc rst */
observer.lat = 55.92; /* 55.92 N */
observer.lng = -3.18; /* 3.18 W */
/* get the julian day from the local system time */
JD = ln_get_julian_from_sys();
printf ("JD %f\n",JD);
/* get the lunar geopcentric position in km, earth is at 0,0,0 */
ln_get_lunar_geo_posn (JD, &moon, 0);
printf ("lunar x %f y %f z %f\n",moon.X, moon.Y, moon.Z);
/* Long Lat */
ln_get_lunar_ecl_coords (JD, &ecl, 0);
printf ("lunar long %f lat %f\n",ecl.lng, ecl.lat);
/* RA, DEC */
ln_get_lunar_equ_coords (JD, &equ);
printf ("lunar RA %f Dec %f\n",equ.ra, equ.dec);
/* moon earth distance */
printf ("lunar distance km %f\n", ln_get_lunar_earth_dist(JD));
/* lunar disk, phase and bright limb */
printf ("lunar disk %f\n", ln_get_lunar_disk(JD));
printf ("lunar phase %f\n", ln_get_lunar_phase(JD));
printf ("lunar bright limb %f\n", ln_get_lunar_bright_limb(JD));
/* rise, set and transit time */
if (ln_get_lunar_rst (JD, &observer, &rst) == 1)
printf ("Moon is circumpolar\n");
else {
ln_get_local_date (rst.rise, &rise);
ln_get_local_date (rst.transit, &transit);
ln_get_local_date (rst.set, &set);
print_date ("Rise", &rise);
print_date ("Transit", &transit);
print_date ("Set", &set);
}
/* rise, set and transit time */
if (ln_get_lunar_rst (JD - 24, &observer, &rst) == 1)
printf ("Moon is circumpolar\n");
else {
ln_get_local_date (rst.rise, &rise);
ln_get_local_date (rst.transit, &transit);
ln_get_local_date (rst.set, &set);
print_date ("Rise", &rise);
print_date ("Transit", &transit);
print_date ("Set", &set);
}
/* rise, set and transit time */
if (ln_get_lunar_rst (JD - 25, &observer, &rst) == 1)
printf ("Moon is circumpolar\n");
else {
ln_get_local_date (rst.rise, &rise);
ln_get_local_date (rst.transit, &transit);
ln_get_local_date (rst.set, &set);
print_date ("Rise", &rise);
print_date ("Transit", &transit);
print_date ("Set", &set);
}
return 0;
}
