91 lines
3.1 KiB
C++
91 lines
3.1 KiB
C++
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/**************************************************************************
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* star.cxx
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* Written by Durk Talsma. Originally started October 1997, for distribution
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* with the FlightGear project. Version 2 was written in August and
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* September 1998. This code is based upon algorithms and data kindly
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* provided by Mr. Paul Schlyter. (pausch@saaf.se).
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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* $Id$
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* (Log is kept at end of this file)
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**************************************************************************/
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#include "star.hxx"
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/*************************************************************************
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* Star::Star(fgTIME *t)
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* Public constructor for class Star
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* Argument: The current time.
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* the hard coded orbital elements our sun are passed to
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* CelestialBody::CelestialBody();
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* note that the word sun is avoided, in order to prevent some compilation
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* problems on sun systems
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************************************************************************/
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Star::Star(fgTIME *t) :
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CelestialBody (0.000000, 0.0000000000,
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0.0000, 0.00000,
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282.9404, 4.7093500E-5,
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1.0000000, 0.000000,
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0.016709, -1.151E-9,
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356.0470, 0.98560025850, t)
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{
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}
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/*************************************************************************
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* void Jupiter::updatePosition(fgTIME *t, Star *ourSun)
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*
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* calculates the current position of our sun.
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*************************************************************************/
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void Star::updatePosition(fgTIME *t)
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{
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double
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actTime, eccAnom,
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xv, yv, v, r,
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xe, ye, ze, ecl;
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updateOrbElements(t);
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actTime = fgCalcActTime(t);
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ecl = DEG_TO_RAD * (23.4393 - 3.563E-7 * actTime); // Angle in Radians
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eccAnom = fgCalcEccAnom(M, e); // Calculate the eccentric Anomaly (also known as solving Kepler's equation)
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xv = cos(eccAnom) - e;
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yv = sqrt (1.0 - e*e) * sin(eccAnom);
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v = atan2 (yv, xv); // the sun's true anomaly
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r = sqrt (xv*xv + yv*yv); // and its distance
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longitude = v + w; // the sun's true longitude
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// convert the sun's true longitude to ecliptic rectangular
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// geocentric coordinates (xs, ys)
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xs = r * cos (longitude);
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ys = r * sin (longitude);
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// convert ecliptic coordinates to equatorial rectangular
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// geocentric coordinates
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xe = xs;
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ye = ys * cos (ecl);
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ze = ys * sin (ecl);
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// And finally, calculate right ascension and declination
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rightAscension = atan2 (ye, xe);
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declination = atan2 (ze, sqrt (xe*xe + ye*ye));
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}
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