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kstars

kssun.cpp

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/***************************************************************************
                          kssun.cpp  -  K Desktop Planetarium
                             -------------------
    begin                : Sun Jul 22 2001
    copyright            : (C) 2001 by Jason Harris
    email                : jharris@30doradus.org
 ***************************************************************************/

/***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/

#include <math.h>
#include <qdatetime.h>

#include "kssun.h"
#include "ksutils.h"
#include "ksnumbers.h"
#include "kstarsdatetime.h"

KSSun::KSSun( KStarsData *kd, QString fn, double pSize ) : KSPlanet( kd, I18N_NOOP( "Sun" ), fn, pSize ) {
    /*
    JD0 = 2447892.5; //Jan 1, 1990
    eclong0 = 279.403303; //mean ecliptic longitude at JD0
    plong0 = 282.768422; //longitude of sun at perigee for JD0
    e0 = 0.016713; //eccentricity of Earth's orbit at JD0
    */
    setMag( -26.73 );
}

bool KSSun::loadData() {
//  kdDebug() << k_funcinfo << endl;
    return (odm.loadData("earth") != 0);
}

bool KSSun::findGeocentricPosition( const KSNumbers *num, const KSPlanetBase *Earth ) {
    if (Earth) {
        //
        // For the precision we need, the earth's orbit is circular.
        // So don't bother to iterate like KSPlanet does. Just subtract
        // The current delay and recompute (once).
        //
        double delay = (.0057755183 * Earth->rsun()) / 365250.0;

        //
        // MHH 2002-02-04 I don't like this. But it avoids code duplication.
        // Maybe we can find a better way.
        //
        const KSPlanet *pEarth = dynamic_cast<const KSPlanet *>(Earth);
        /* FIXME: if you use pEarth at some point again, make sure you
            check for 0L after the dynamic_cast! */
        EclipticPosition trialpos;
        pEarth->calcEcliptic(num->julianMillenia() - delay, trialpos);

        setEcLong( trialpos.longitude.Degrees() + 180.0 );
        setEcLong( ecLong()->reduce().Degrees() );
        setEcLat( -1.0*trialpos.latitude.Degrees() );

    } else {
        double sum[6];
        dms EarthLong, EarthLat; //heliocentric coords of Earth
        OrbitDataColl * odc;
        double T = num->julianMillenia(); //Julian millenia since J2000
        double Tpow[6];

        Tpow[0] = 1.0;
        for (int i=1; i<6; ++i) {
            Tpow[i] = Tpow[i-1] * T;
        }
            //First, find heliocentric coordinates

        if (!(odc =  odm.loadData("earth"))) return false;

        //Ecliptic Longitude
        for (int i=0; i<6; ++i) {
            sum[i] = 0.0;
            for (uint j = 0; j < odc->Lon[i].size(); ++j) {
                sum[i] += odc->Lon[i][j]->A * cos( odc->Lon[i][j]->B + odc->Lon[i][j]->C*T );
            }
            sum[i] *= Tpow[i];
            //kdDebug() << name() << " : sum[" << i << "] = " << sum[i] <<endl;
        }

        EarthLong.setRadians( sum[0] + sum[1] + sum[2] +
                sum[3] + sum[4] + sum[5] );
        EarthLong.setD( EarthLong.reduce().Degrees() );

        //Compute Ecliptic Latitude
        for (int i=0; i<6; ++i) {
            sum[i] = 0.0;
            for (uint j = 0; j < odc->Lat[i].size(); ++j) {
                sum[i] += odc->Lat[i][j]->A * cos( odc->Lat[i][j]->B + odc->Lat[i][j]->C*T );
            }
            sum[i] *= Tpow[i];
        }


        EarthLat.setRadians( sum[0] + sum[1] + sum[2] + sum[3] +
                sum[4] + sum[5] );

        //Compute Heliocentric Distance
        for (int i=0; i<6; ++i) {
            sum[i] = 0.0;
            for (uint j = 0; j < odc->Dst[i].size(); ++j) {
                sum[i] += odc->Dst[i][j]->A * cos( odc->Dst[i][j]->B + odc->Dst[i][j]->C*T );
            }
            sum[i] *= Tpow[i];
        }

        ep.radius = sum[0] + sum[1] + sum[2] + sum[3] + sum[4] + sum[5];

        setEcLong( EarthLong.Degrees() + 180.0 );
        setEcLong( ecLong()->reduce().Degrees() );
        setEcLat( -1.0*EarthLat.Degrees() );
    }

    //Finally, convert Ecliptic coords to Ra, Dec.  Ecliptic latitude is zero, by definition
    EclipticToEquatorial( num->obliquity() );

    nutate(num);
    aberrate(num);

    // We obtain the apparent geocentric ecliptic coordinates. That is, after 
    // nutation and aberration have been applied.
    EquatorialToEcliptic( num->obliquity() );
    
    //Determine the position angle
    findPA( num );

    return true;
}

long double KSSun::springEquinox(int year) {
    return equinox(year, 18, 3, 0.);
}

long double KSSun::summerSolstice(int year) {
    return equinox(year, 18, 6, 90.);
}

long double KSSun::autumnEquinox(int year) {
    return equinox(year, 19, 9, 180.);
}

long double KSSun::winterSolstice(int year) {
    return equinox(year, 18, 12, 270.);
}

long double KSSun::equinox(int year, int d, int m, double angle) {
    long double jd0[5];
    long double eclipticLongitude[5];
    
    for(int i = 0; i<5; ++i) {
        jd0[i] = KStarsDateTime( ExtDate(year,m,d+i), QTime(0,0,0) ).djd();
        KSNumbers *ksn = new KSNumbers(jd0[i]);
        //FIXME this is the Earth position
        findGeocentricPosition( ksn );
        delete ksn;
        eclipticLongitude[i] = (long double)ecLong()->Degrees();
    }

    return KSUtils::lagrangeInterpolation( eclipticLongitude, jd0, 5, angle );
}

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