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 library is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Library General Public
10 * License as published by the Free Software Foundation; either
11 * version 2 of the License, or (at your option) any later version.
13 * This library is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Library General Public License for more details.
18 * You should have received a copy of the GNU Library General Public
19 * License along with this library; if not, write to the
20 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
21 * Boston, MA 02111-1307, USA.
24 **************************************************************************/
28 # define exception c_exception
32 #include <simgear/debug/logstream.hxx>
37 /*************************************************************************
38 * Star::Star(double mjd)
39 * Public constructor for class Star
40 * Argument: The current time.
41 * the hard coded orbital elements our sun are passed to
42 * CelestialBody::CelestialBody();
43 * note that the word sun is avoided, in order to prevent some compilation
44 * problems on sun systems
45 ************************************************************************/
46 Star::Star(double mjd) :
47 CelestialBody (0.000000, 0.0000000000,
49 282.9404, 4.7093500E-5,
52 356.0470, 0.98560025850, mjd)
58 CelestialBody (0.000000, 0.0000000000,
60 282.9404, 4.7093500E-5,
63 356.0470, 0.98560025850)
73 /*************************************************************************
74 * void Star::updatePosition(double mjd, Star *ourSun)
76 * calculates the current position of our sun.
77 *************************************************************************/
78 void Star::updatePosition(double mjd)
85 updateOrbElements(mjd);
87 actTime = sgCalcActTime(mjd);
88 ecl = DEG_TO_RAD * (23.4393 - 3.563E-7 * actTime); // Angle in Radians
89 eccAnom = sgCalcEccAnom(M, e); // Calculate the eccentric Anomaly (also known as solving Kepler's equation)
91 xv = cos(eccAnom) - e;
92 yv = sqrt (1.0 - e*e) * sin(eccAnom);
93 v = atan2 (yv, xv); // the sun's true anomaly
94 distance = r = sqrt (xv*xv + yv*yv); // and its distance
96 lonEcl = v + w; // the sun's true longitude
99 // convert the sun's true longitude to ecliptic rectangular
100 // geocentric coordinates (xs, ys)
101 xs = r * cos (lonEcl);
102 ys = r * sin (lonEcl);
104 // convert ecliptic coordinates to equatorial rectangular
105 // geocentric coordinates
111 // And finally, calculate right ascension and declination
112 rightAscension = atan2 (ye, xe);
113 declination = atan2 (ze, sqrt (xe*xe + ye*ye));