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kstars

kstarsdatetime.cpp

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 /***************************************************************************
                          kstarsdatetime.cpp  -  K Desktop Planetarium
                             -------------------
    begin                : Tue 05 May 2004
    copyright            : (C) 2004 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 <kdebug.h>
 
#include "kstarsdatetime.h"
#include "ksnumbers.h"
#include "dms.h"

KStarsDateTime::KStarsDateTime() : ExtDateTime() {
    setDJD( J2000 );
}

KStarsDateTime::KStarsDateTime( long int _jd ) : ExtDateTime(){
    setDJD( (long double)( _jd ) );
}

KStarsDateTime::KStarsDateTime( const KStarsDateTime &kdt ) : ExtDateTime() {
    setDJD( kdt.djd() );
}

KStarsDateTime::KStarsDateTime( const ExtDateTime &edt ) : ExtDateTime( edt ) {
    //don't call setDJD() because we don't need to compute the time; just set DJD directly
    QTime _t = edt.time();
    ExtDate _d = edt.date();
    long double jdFrac = ( _t.hour()-12 + ( _t.minute() + ( _t.second() + _t.msec()/1000.)/60.)/60.)/24.;
    DJD = (long double)( _d.jd() ) + jdFrac;
}

KStarsDateTime::KStarsDateTime( const ExtDate &_d, const QTime &_t ) : ExtDateTime( _d, _t ) {
    //don't call setDJD() because we don't need to compute the time; just set DJD directly
    long double jdFrac = ( _t.hour()-12 + ( _t.minute() + ( _t.second() + _t.msec()/1000.)/60.)/60.)/24.;
    DJD = (long double)( _d.jd() ) + jdFrac;
}

KStarsDateTime::KStarsDateTime( double _jd ) : ExtDateTime() {
    setDJD( (long double)_jd );
}

KStarsDateTime::KStarsDateTime( long double _jd ) : ExtDateTime() {
    setDJD( _jd );
}

KStarsDateTime KStarsDateTime::currentDateTime() {
    KStarsDateTime dt( ExtDate::currentDate(), QTime::currentTime() );
    if ( dt.time().hour()==0 && dt.time().minute()==0 ) // midnight or right after?
            dt.setDate( ExtDate::currentDate() );         // fetch date again
    
    return dt;
}

void KStarsDateTime::setDJD( long double _jd ) {
    DJD = _jd;

    ExtDate dd;
    dd.setJD( (long int)( _jd + 0.5 ) );
    ExtDateTime::setDate( dd );

    double dayfrac = _jd - (double)( date().jd() ) + 0.5;
    if ( dayfrac > 1.0 ) dayfrac -= 1.0;
    double hour = 24.*dayfrac;
    int h = int(hour);
    int m = int( 60.*(hour - h) );
    int s = int( 60.*(60.*(hour - h) - m) );
    int ms = int( 1000.*(60.*(60.*(hour - h) - m) - s) );

    ExtDateTime::setTime( QTime( h, m, s, ms ) );
}

void KStarsDateTime::setDate( const ExtDate &_d ) {
    //Save the JD fraction
    long double jdFrac = djd() - (long double)( date().jd() );
    
    //set the integer portion of the JD and add back the JD fraction:
    setDJD( (long double)_d.jd() + jdFrac );
}

void KStarsDateTime::setTime( const QTime &_t ) {
    KStarsDateTime _dt( date(), _t );
    setDJD( _dt.djd() );
}

dms KStarsDateTime::gst() const {
    dms gst0 = GSTat0hUT();

    double hr = double( time().hour() );
    double mn = double( time().minute() );
    double sc = double( time().second() ) + double ( 0.001 * time().msec() );
    double st = (hr + ( mn + sc/60.0)/60.0)*SIDEREALSECOND;

    dms gst = dms( gst0.Degrees() + st*15.0 ).reduce();
    return gst;
}

dms KStarsDateTime::GSTat0hUT() const {
    double sinOb, cosOb;

    // Mean greenwich sidereal time
    KStarsDateTime t0( date(), QTime( 0, 0, 0 ) );
    long double s = t0.djd() - J2000;
    double t = s/36525.0;
    double t1 = 6.697374558 + 2400.051336*t + 0.000025862*t*t +
        0.000000002*t*t*t;

    // To obtain the apparent sidereal time, we have to correct the
    // mean greenwich sidereal time with nutation in longitude multiplied
    // by the cosine of the obliquity of the ecliptic. This correction
    // is called nutation in right ascention, and may amount to 0.3 secs.
    KSNumbers num( t0.djd() );
    num.obliquity()->SinCos( sinOb, cosOb );

    // nutLong has to be in hours of time since t1 is hours of time.
    double nutLong = num.dEcLong()*cosOb/15.0;
    t1 += nutLong;

    dms gst;
    gst.setH( t1 );
    return gst.reduce();
}

QTime KStarsDateTime::GSTtoUT( dms GST ) const {
    dms gst0 = GSTat0hUT();

    //dt is the number of sidereal hours since UT 0h.
    double dt = GST.Hours() - gst0.Hours();
    while ( dt < 0.0 ) dt += 24.0;
    while ( dt >= 24.0 ) dt -= 24.0;

    //convert to solar time.  dt is now the number of hours since 0h UT.
    dt /= SIDEREALSECOND;

    int hr = int( dt );
    int mn = int( 60.0*( dt - double( hr ) ) );
    int sc = int( 60.0*( 60.0*( dt - double( hr ) ) - double( mn ) ) );
    int ms = int( 1000.0*( 60.0*( 60.0*( dt - double(hr) ) - double(mn) ) - double(sc) ) );
    
    return( QTime( hr, mn, sc, ms ) );
}

void KStarsDateTime::setFromEpoch( double epoch ) {
    if (epoch == 1950.0) {
        setDJD( 2433282.4235 );
    } else if ( epoch == 2000.0 ) {
        setDJD( J2000 );
    } else {
        int year = int( epoch );
        KStarsDateTime dt( ExtDate( year, 1, 1 ), QTime( 0, 0, 0 ) );
        double days = (double)(dt.date().daysInYear())*( epoch - (double)year );
        dt = dt.addSecs( days*86400. ); //set date and time based on the number of days into the year
        setDJD( dt.djd() );
    }
}

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