1 /**************************************************************************
3 * Written by Durk Talsma. Originally started October 1997, for distribution
4 * with the FlightGear project. Version 2 was written in August and
5 * September 1998. This code is based upon algorithms and data kindly
6 * provided by Mr. Paul Schlyter. (pausch@saaf.se).
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public License as
10 * published by the Free Software Foundation; either version 2 of the
11 * License, or (at your option) any later version.
13 * This program is distributed in the hope that it will be useful, but
14 * WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * General Public License for more details.
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
23 **************************************************************************/
27 # define exception c_exception
31 #include <simgear/debug/logstream.hxx>
33 #include <Time/sunpos.hxx>
34 #include <Time/light.hxx>
35 #include <Main/options.hxx>
40 /*************************************************************************
41 * Star::Star(FGTime *t)
42 * Public constructor for class Star
43 * Argument: The current time.
44 * the hard coded orbital elements our sun are passed to
45 * CelestialBody::CelestialBody();
46 * note that the word sun is avoided, in order to prevent some compilation
47 * problems on sun systems
48 ************************************************************************/
49 Star::Star(FGTime *t) :
50 CelestialBody (0.000000, 0.0000000000,
52 282.9404, 4.7093500E-5,
55 356.0470, 0.98560025850, t)
61 CelestialBody (0.000000, 0.0000000000,
63 282.9404, 4.7093500E-5,
66 356.0470, 0.98560025850)
76 /*************************************************************************
77 * void Star::updatePosition(FGTime *t, Star *ourSun)
79 * calculates the current position of our sun.
80 *************************************************************************/
81 void Star::updatePosition(FGTime *t)
90 actTime = fgCalcActTime(t);
91 ecl = DEG_TO_RAD * (23.4393 - 3.563E-7 * actTime); // Angle in Radians
92 eccAnom = fgCalcEccAnom(M, e); // Calculate the eccentric Anomaly (also known as solving Kepler's equation)
94 xv = cos(eccAnom) - e;
95 yv = sqrt (1.0 - e*e) * sin(eccAnom);
96 v = atan2 (yv, xv); // the sun's true anomaly
97 distance = r = sqrt (xv*xv + yv*yv); // and its distance
99 lonEcl = v + w; // the sun's true longitude
102 // convert the sun's true longitude to ecliptic rectangular
103 // geocentric coordinates (xs, ys)
104 xs = r * cos (lonEcl);
105 ys = r * sin (lonEcl);
107 // convert ecliptic coordinates to equatorial rectangular
108 // geocentric coordinates
114 // And finally, calculate right ascension and declination
115 rightAscension = atan2 (ye, xe);
116 declination = atan2 (ze, sqrt (xe*xe + ye*ye));