double
MoonPhases::FindNext( double julianDay, Angle phaseAngle )
{
const double synodicMonth = 29.5305888531;
Angle lunarPhase = LunarPhase( julianDay );
Angle phaseDiff = phaseAngle - lunarPhase;
phaseDiff.NormalizePositive( );
double offset = phaseDiff.Cycles() * synodicMonth;
double estimate = julianDay + offset;
double lowEst = estimate - 0.5;
double highEst = estimate + 0.5;
MoonPhaseFunc phaseFunc( phaseAngle );
#ifdef DEBUG
bool brcktRslt =
#endif
RootFinder::BracketRoot( phaseFunc, &lowEst, &highEst );
Assert( brcktRslt );
double phaseJD;
#ifdef DEBUG
bool rootRslt =
#endif
RootFinder::Brent( phaseFunc, &phaseJD, lowEst, highEst, 1.e-4 );
Assert( rootRslt );
double ut_tdb = - TDB_UT( phaseJD ).Days();
return (phaseJD + ut_tdb);
}
TimeIncrement
EquationOfTime( double julianDay )
{
shared_ptr< JPLEphemeris > spEphem
= JPLEphemeris::GetEphemeris( julianDay );
if ( ! spEphem )
return TimeIncrement( 0 );
Angle meanSolarLong = MeanSolarLongitude( julianDay );
Point3D earthBarycentric;
Vector3D earthBarycentricVelocity;
#ifdef DEBUG
bool earthRslt =
#endif
GetEarthBarycentric( julianDay, &earthBarycentric,
&earthBarycentricVelocity, spEphem );
Assert( earthRslt );
Matrix3D precessionMatrix = Precession( julianDay ).Matrix( );
Nutation nutation( 0., 0. );
if ( spEphem->NutationAvailable() )
{
#ifdef DEBUG
bool nutRslt =
#endif
spEphem->GetNutation( julianDay, &nutation );
Assert( nutRslt );
}
Angle meanObliquity = MeanObliquity( julianDay );
Angle trueObliquity = TrueObliquity( meanObliquity, nutation );
Matrix3D nutAndPrecMatrix = nutation.Matrix( meanObliquity )
* precessionMatrix;
JPLBarycentricEphemeris sunEphem( spEphem, JPLEphemeris::Sun );
Point3D sunPos = GetSunApparentPlace( julianDay, sunEphem,
earthBarycentric,
earthBarycentricVelocity,
nutAndPrecMatrix );
Equatorial sunEquatorial( sunPos );
Angle eotAngle = meanSolarLong - Angle( 0.0057183, Angle::Degree )
- sunEquatorial.RightAscension()
+ nutation.NutLongitude() * Cos( trueObliquity );
return TimeIncrement( eotAngle.Cycles() );
}