libnova v 0.15.0

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comet.c

Examples of how to use comet functions.

/*
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU Library General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
Copyright (C) 2003 Liam Girdwood <liam@gnova.org>
A simple example showing some comet calculations.
Comet Enckle
*/
#include <stdio.h>
#include <libnova/comet.h>
#include <libnova/julian_day.h>
#include <libnova/rise_set.h>
#include <libnova/transform.h>
#include <libnova/elliptic_motion.h>
void print_date (char * title, struct ln_zonedate* date)
{
printf ("\n%s\n",title);
printf (" Year : %d\n", date->years);
printf (" Month : %d\n", date->months);
printf (" Day : %d\n", date->days);
printf (" Hours : %d\n", date->hours);
printf (" Minutes : %d\n", date->minutes);
printf (" Seconds : %f\n", date->seconds);
printf("gmtoff %ld\n", date->gmtoff);
}
int main (int argc, char * argv[])
{
struct ln_equ_posn equ;
struct ln_rst_time rst;
struct ln_zonedate rise, set, transit;
struct ln_date epoch_date;
struct ln_lnlat_posn observer;
struct ln_ell_orbit orbit;
struct ln_rect_posn posn;
double JD, e_JD;
double E, v, V, r, l, dist;
/* observers location (Edinburgh), used to calc rst */
observer.lat = 55.92; /* 55.92 N */
observer.lng = -3.18; /* 3.18 W */
/* get Julian day from local time */
JD = ln_get_julian_from_sys();
printf ("JD %f\n", JD);
/* calc epoch JD */
epoch_date.years = 1990;
epoch_date.months = 10;
epoch_date.days = 28;
epoch_date.hours = 12;
epoch_date.minutes = 30;
epoch_date.seconds = 0;
e_JD = ln_get_julian_day (&epoch_date);
/* Enckle orbital elements */
orbit.JD = e_JD;
orbit.a = 2.2091404;
orbit.e = 0.8502196;
orbit.i = 11.94525;
orbit.omega = 334.75006;
orbit.w = 186.23352;
orbit.n = 0;
/* solve kepler for orbit */
E = ln_solve_kepler (0.1, 5.0);
printf("(Equation of kepler) E when e is 0.1 and M is 5.0 %f\n ", E);
/* true anomaly */
v = ln_get_ell_true_anomaly (0.1, E);
printf("(True Anomaly) v when e is 0.1 and E is 5.5545 %f\n ", v);
/* radius vector */
r = ln_get_ell_radius_vector (0.5, 0.1, E);
printf ("(Radius Vector) r when v is , e is 0.1 and E is 5.5545 %f\n ", r);
/* geocentric rect coords */
ln_get_ell_geo_rect_posn (&orbit, JD, &posn);
printf ("(Geocentric Rect Coords X) for comet Enckle %f\n", posn.X);
printf ("(Geocentric Rect Coords Y) for comet Enckle %f\n", posn.Y);
printf ("(Geocentric Rect Coords Z) for comet Enckle %f\n", posn.Z);
/* rectangular coords */
ln_get_ell_helio_rect_posn (&orbit, JD, &posn);
printf ("(Heliocentric Rect Coords X) for comet Enckle %f\n ", posn.X);
printf ("(Heliocentric Rect Coords Y) for comet Enckle %f\n ", posn.Y);
printf ("(Heliocentric Rect Coords Z) for comet Enckle %f\n ", posn.Z);
/* ra, dec */
ln_get_ell_body_equ_coords (JD, &orbit, &equ);
printf ("(RA) for comet Enckle %f\n ", equ.ra);
printf ("(Dec) for comet Enckle %f\n ", equ.dec);
/* orbit length */
l = ln_get_ell_orbit_len (&orbit);
printf ("(Orbit Length) for comet Enckle in AU %f\n ", l);
/* orbital velocity at perihelion */
V = ln_get_ell_orbit_pvel (&orbit);
printf ("(Orbit Perihelion Vel) for comet Enckle in kms %f\n ", V);
/* orbital velocity at aphelion */
V = ln_get_ell_orbit_avel (&orbit);
printf ("(Orbit Aphelion Vel) for comet Enckle in kms %f\n ", V);
/* average orbital velocity */
V = ln_get_ell_orbit_vel (JD, &orbit);
printf ("(Orbit Vel JD) for comet Enckle in kms %f\n ", V);
/* comet sun distance */
dist = ln_get_ell_body_solar_dist (JD, &orbit);
printf ("(Body Solar Dist) for comet Enckle in AU %f\n ", dist);
/* comet earth distance */
dist = ln_get_ell_body_earth_dist (JD, &orbit);
printf ("(Body Earth Dist) for comet Enckle in AU %f\n ", dist);
/* rise, set and transit */
if (ln_get_ell_body_rst (JD, &observer, &orbit, &rst) == 1)
printf ("Comet 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;
}