1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
|
/*
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 <lgirdwood@gmail.com>
A simple example showing some comet calculations.
Comet Encke
*/
#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>
/* use the orbital example from Meeus book */
#define MEEUS 0
static void print_date(const char *title, struct ln_zonedate *date)
{
fprintf(stdout, "\n%s\n",title);
fprintf(stdout, " Year : %d\n", date->years);
fprintf(stdout, " Month : %d\n", date->months);
fprintf(stdout, " Day : %d\n", date->days);
fprintf(stdout, " Hours : %d\n", date->hours);
fprintf(stdout, " Minutes : %d\n", date->minutes);
fprintf(stdout, " Seconds : %f\n", date->seconds);
fprintf(stdout, " GMT offset %ld\n", date->gmtoff);
}
int main (int argc, const char *argv[])
{
struct ln_equ_posn equ;
struct ln_rst_time rst;
struct ln_zonedate rise, set, transit;
#if MEEUS
struct ln_date epoch_date, date;
#endif
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, M;
/* observers location (Edinburgh), used to calc rst */
observer.lat = 55.92; /* 55.92 N */
observer.lng = -3.18; /* 3.18 W */
#if MEEUS
date.years = 1990;
date.months = 10;
date.days = 6;
date.hours = 0;
date.minutes = 0;
date.seconds = 0;
JD = ln_get_julian_day(&date);
#else
/* get Julian day from local time */
JD = ln_get_julian_from_sys();
fprintf(stdout, "JD %f\n", JD);
#endif
/* calc epoch JD */
#if MEEUS
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);
#else
e_JD = 2456617.5;
#endif
fprintf(stdout, "Epoch JD %f diff %f\n", e_JD, JD - e_JD);
/* Encke orbital elements */
#if MEEUS
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;
#else
orbit.JD = e_JD;
orbit.a = 2.214743;
orbit.e = 0.848232;
orbit.i = 11.7790;
orbit.omega = 334.5731;
orbit.w = 186.5356;
orbit.n = 0;//0.2990330;
#endif
/* get mean anomaly */
if (orbit.n == 0.0)
orbit.n = ln_get_ell_mean_motion(orbit.a);
M = ln_get_ell_mean_anomaly(orbit.n, JD - orbit.JD);
fprintf(stdout,
"(Mean Anomaly) M when n is %f and JD diff is %f = %f\n",
orbit.n, JD - orbit.JD, M);
/* solve kepler for orbit */
E = ln_solve_kepler(orbit.e, M);
fprintf(stdout,
"(Equation of kepler) E when e is %f and M is %f = %f\n",
orbit.e, M, E);
/* true anomaly */
v = ln_get_ell_true_anomaly(orbit.e, E);
fprintf(stdout,
"(True Anomaly) v when e is %f and E is %f = %f\n", orbit.e, E, v);
/* radius vector */
r = ln_get_ell_radius_vector(M, orbit.e, E);
fprintf(stdout,
"(Radius Vector) r when e is %f and E is %f = %f\n", orbit.e, E, r);
/* geocentric rect coords */
ln_get_ell_geo_rect_posn(&orbit, JD, &posn);
fprintf(stdout,
"(Geocentric Rect Coords X) for comet Encke %f\n", posn.X);
fprintf(stdout,
"(Geocentric Rect Coords Y) for comet Encke %f\n", posn.Y);
fprintf(stdout,
"(Geocentric Rect Coords Z) for comet Encke %f\n", posn.Z);
/* rectangular coords */
ln_get_ell_helio_rect_posn(&orbit, JD, &posn);
fprintf(stdout,
"(Heliocentric Rect Coords X) for comet Encke %f\n", posn.X);
fprintf(stdout,
"(Heliocentric Rect Coords Y) for comet Encke %f\n", posn.Y);
fprintf(stdout,
"(Heliocentric Rect Coords Z) for comet Encke %f\n", posn.Z);
/* ra, dec */
ln_get_ell_body_equ_coords(JD, &orbit, &equ);
fprintf(stdout, "(RA) for comet Encke %f\n", equ.ra);
fprintf(stdout, "(Dec) for comet Encke %f\n", equ.dec);
/* orbit length */
l = ln_get_ell_orbit_len(&orbit);
fprintf(stdout, "(Orbit Length) for comet Encke in AU %f\n", l);
/* orbital velocity at perihelion */
V = ln_get_ell_orbit_pvel(&orbit);
fprintf(stdout,
"(Orbit Perihelion Vel) for comet Encke in kms %f\n", V);
/* orbital velocity at aphelion */
V = ln_get_ell_orbit_avel(&orbit);
fprintf(stdout, "(Orbit Aphelion Vel) for comet Encke in kms %f\n", V);
/* average orbital velocity */
V = ln_get_ell_orbit_vel(JD, &orbit);
fprintf(stdout, "(Orbit Vel JD) for comet Encke in kms %f\n", V);
/* comet sun distance */
dist = ln_get_ell_body_solar_dist(JD, &orbit);
fprintf(stdout, "(Body Solar Dist) for comet Encke in AU %f\n", dist);
/* comet earth distance */
dist = ln_get_ell_body_earth_dist(JD, &orbit);
fprintf(stdout, "(Body Earth Dist) for comet Encke in AU %f\n", dist);
/* rise, set and transit */
if (ln_get_ell_body_rst(JD, &observer, &orbit, &rst) != 0)
fprintf(stdout, "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;
}
|
