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 * (Log is kept at end of this file)
24 **************************************************************************/
27 # define exception c_exception
33 /*************************************************************************
34 * Star::Star(fgTIME *t)
35 * Public constructor for class Star
36 * Argument: The current time.
37 * the hard coded orbital elements our sun are passed to
38 * CelestialBody::CelestialBody();
39 * note that the word sun is avoided, in order to prevent some compilation
40 * problems on sun systems
41 ************************************************************************/
42 Star::Star(fgTIME *t) :
43 CelestialBody (0.000000, 0.0000000000,
45 282.9404, 4.7093500E-5,
48 356.0470, 0.98560025850, t)
51 /*************************************************************************
52 * void Jupiter::updatePosition(fgTIME *t, Star *ourSun)
54 * calculates the current position of our sun.
55 *************************************************************************/
56 void Star::updatePosition(fgTIME *t)
65 actTime = fgCalcActTime(t);
66 ecl = DEG_TO_RAD * (23.4393 - 3.563E-7 * actTime); // Angle in Radians
67 eccAnom = fgCalcEccAnom(M, e); // Calculate the eccentric Anomaly (also known as solving Kepler's equation)
69 xv = cos(eccAnom) - e;
70 yv = sqrt (1.0 - e*e) * sin(eccAnom);
71 v = atan2 (yv, xv); // the sun's true anomaly
72 distance = r = sqrt (xv*xv + yv*yv); // and its distance
74 longitude = v + w; // the sun's true longitude
76 // convert the sun's true longitude to ecliptic rectangular
77 // geocentric coordinates (xs, ys)
78 xs = r * cos (longitude);
79 ys = r * sin (longitude);
81 // convert ecliptic coordinates to equatorial rectangular
82 // geocentric coordinates
88 // And finally, calculate right ascension and declination
89 rightAscension = atan2 (ye, xe);
90 declination = atan2 (ze, sqrt (xe*xe + ye*ye));