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 General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
23 **************************************************************************/
27 # define exception c_exception
31 #include <simgear/debug/logstream.hxx>
36 /*************************************************************************
37 * Star::Star(double mjd)
38 * Public constructor for class Star
39 * Argument: The current time.
40 * the hard coded orbital elements our sun are passed to
41 * CelestialBody::CelestialBody();
42 * note that the word sun is avoided, in order to prevent some compilation
43 * problems on sun systems
44 ************************************************************************/
45 Star::Star(double mjd) :
46 CelestialBody (0.000000, 0.0000000000,
48 282.9404, 4.7093500E-5,
51 356.0470, 0.98560025850, mjd)
57 CelestialBody (0.000000, 0.0000000000,
59 282.9404, 4.7093500E-5,
62 356.0470, 0.98560025850)
72 /*************************************************************************
73 * void Star::updatePosition(double mjd, Star *ourSun)
75 * calculates the current position of our sun.
76 *************************************************************************/
77 void Star::updatePosition(double mjd)
84 updateOrbElements(mjd);
86 actTime = sgCalcActTime(mjd);
87 ecl = SGD_DEGREES_TO_RADIANS * (23.4393 - 3.563E-7 * actTime); // Angle in Radians
88 eccAnom = sgCalcEccAnom(M, e); // Calculate the eccentric Anomaly (also known as solving Kepler's equation)
90 xv = cos(eccAnom) - e;
91 yv = sqrt (1.0 - e*e) * sin(eccAnom);
92 v = atan2 (yv, xv); // the sun's true anomaly
93 distance = r = sqrt (xv*xv + yv*yv); // and its distance
95 lonEcl = v + w; // the sun's true longitude
98 // convert the sun's true longitude to ecliptic rectangular
99 // geocentric coordinates (xs, ys)
100 xs = r * cos (lonEcl);
101 ys = r * sin (lonEcl);
103 // convert ecliptic coordinates to equatorial rectangular
104 // geocentric coordinates
110 // And finally, calculate right ascension and declination
111 rightAscension = atan2 (ye, xe);
112 declination = atan2 (ze, sqrt (xe*xe + ye*ye));