float MinorPlanet::getVMagnitude(const StelCore* core) const
{
//If the H-G system is not used, use the default radius/albedo mechanism
if (slopeParameter < 0)
{
return Planet::getVMagnitude(core);
}
//Calculate phase angle
//(Code copied from Planet::getVMagnitude())
//(this is actually vector subtraction + the cosine theorem :))
const Vec3d& observerHelioPos = core->getObserverHeliocentricEclipticPos();
const float observerRq = observerHelioPos.lengthSquared();
const Vec3d& planetHelioPos = getHeliocentricEclipticPos();
const float planetRq = planetHelioPos.lengthSquared();
const float observerPlanetRq = (observerHelioPos - planetHelioPos).lengthSquared();
const float cos_chi = (observerPlanetRq + planetRq - observerRq)/(2.0*std::sqrt(observerPlanetRq*planetRq));
const float phaseAngle = std::acos(cos_chi);
//Calculate reduced magnitude (magnitude without the influence of distance)
//Source of the formulae: http://www.britastro.org/asteroids/dymock4.pdf
const float tanPhaseAngleHalf=std::tan(phaseAngle*0.5f);
const float phi1 = std::exp(-3.33f * std::pow(tanPhaseAngleHalf, 0.63f));
const float phi2 = std::exp(-1.87f * std::pow(tanPhaseAngleHalf, 1.22f));
float reducedMagnitude = absoluteMagnitude - 2.5f * std::log10( (1.0f - slopeParameter) * phi1 + slopeParameter * phi2 );
//Calculate apparent magnitude
float apparentMagnitude = reducedMagnitude + 5.0f * std::log10(std::sqrt(planetRq * observerPlanetRq));
return apparentMagnitude;
}
float MinorPlanet::getVMagnitude(const StelCore* core) const
{
//If the H-G system is not used, use the default radius/albedo mechanism
if (slopeParameter < 0)
{
return Planet::getVMagnitude(core);
}
//Calculate phase angle
//(Code copied from Planet::getVMagnitude())
//(LOL, this is actually vector subtraction + the cosine theorem :))
const Vec3d& observerHelioPos = core->getObserverHeliocentricEclipticPos();
const double observerRq = observerHelioPos.lengthSquared();
const Vec3d& planetHelioPos = getHeliocentricEclipticPos();
const double planetRq = planetHelioPos.lengthSquared();
const double observerPlanetRq = (observerHelioPos - planetHelioPos).lengthSquared();
const double cos_chi = (observerPlanetRq + planetRq - observerRq)/(2.0*sqrt(observerPlanetRq*planetRq));
double phaseAngle = std::acos(cos_chi);
//Calculate reduced magnitude (magnitude without the influence of distance)
//Source of the formulae: http://www.britastro.org/asteroids/dymock4.pdf
const double phi1 = std::exp(-3.33 * std::pow(std::tan(phaseAngle/2), 0.63));
const double phi2 = std::exp(-1.87 * std::pow(std::tan(phaseAngle/2), 1.22));
double reducedMagnitude = absoluteMagnitude - 2.5 * std::log10( (1 - slopeParameter) * phi1 + slopeParameter * phi2 );
//Calculate apparent magnitude
//TODO: See if you can "collapse" some calculations
// -- GZ: NO! This is also in Meeus, Astr.Alg. 1998, p.231 and authoritative by IAU commission 20, New Delhi November 1985.
// (you can collapse and leave away the reducedMagnitude varable, but this is cosmetic)
double apparentMagnitude = reducedMagnitude + 5 * std::log10(std::sqrt(planetRq * observerPlanetRq));
return apparentMagnitude;
}
float Comet::getVMagnitude(const StelCore* core, bool withExtinction) const
{
//If the two parameter system is not used,
//use the default radius/albedo mechanism
if (slopeParameter < 0)
{
return Planet::getVMagnitude(core, withExtinction);
}
float extinctionMag=0.0; // track magnitude loss
if (withExtinction && core->getSkyDrawer()->getFlagHasAtmosphere())
{
Vec3d altAz=getAltAzPosApparent(core);
altAz.normalize();
core->getSkyDrawer()->getExtinction().forward(&altAz[2], &extinctionMag);
}
//Calculate distances
const Vec3d& observerHeliocentricPosition = core->getObserverHeliocentricEclipticPos();
const Vec3d& cometHeliocentricPosition = getHeliocentricEclipticPos();
const double cometSunDistance = std::sqrt(cometHeliocentricPosition.lengthSquared());
const double observerCometDistance = std::sqrt((observerHeliocentricPosition - cometHeliocentricPosition).lengthSquared());
//Calculate apparent magnitude
//Sources: http://www.clearskyinstitute.com/xephem/help/xephem.html#mozTocId564354
//(XEphem manual, section 7.1.2.3 "Magnitude models"), also
//http://www.ayton.id.au/gary/Science/Astronomy/Ast_comets.htm#Comet%20facts:
double apparentMagnitude = absoluteMagnitude + 5 * std::log10(observerCometDistance) + 2.5 * slopeParameter * std::log10(cometSunDistance);
return apparentMagnitude + extinctionMag;
}
float Comet::getVMagnitude(const StelCore* core) const
{
//If the two parameter system is not used,
//use the default radius/albedo mechanism
if (slopeParameter < 0)
{
return Planet::getVMagnitude(core);
}
//Calculate distances
const Vec3d& observerHeliocentricPosition = core->getObserverHeliocentricEclipticPos();
const Vec3d& cometHeliocentricPosition = getHeliocentricEclipticPos();
const double cometSunDistance = cometHeliocentricPosition.length();
const double observerCometDistance = (observerHeliocentricPosition - cometHeliocentricPosition).length();
//Calculate apparent magnitude
//Sources: http://www.clearskyinstitute.com/xephem/help/xephem.html#mozTocId564354
//(XEphem manual, section 7.1.2.3 "Magnitude models"), also
//http://www.ayton.id.au/gary/Science/Astronomy/Ast_comets.htm#Comet%20facts:
// GZ: Note that Meeus, Astr.Alg.1998 p.231, has m=absoluteMagnitude+5log10(observerCometDistance) + kappa*log10(cometSunDistance)
// with kappa typically 5..15. MPC provides Slope parameter. So we should expect to have slopeParameter (a word only used for minor planets!) for our comets 2..6
double apparentMagnitude = absoluteMagnitude + 5 * std::log10(observerCometDistance) + 2.5 * slopeParameter * std::log10(cometSunDistance);
return apparentMagnitude;
}
// Formula found at http://www.projectpluto.com/update7b.htm#comet_tail_formula
Vec2f Comet::getComaDiameterAndTailLengthAU() const
{
float r = getHeliocentricEclipticPos().length();
float mhelio = absoluteMagnitude + slopeParameter * log10(r);
float Do = pow(10.0f, ((-0.0033f*mhelio - 0.07f) * mhelio + 3.25f));
float common = 1.0f - pow(10.0f, (-2.0f*r));
float D = Do * common * (1.0f - pow(10.0f, -r)) * (1000.0f*AU_KM);
float Lo = pow(10.0f, ((-0.0075f*mhelio - 0.19f) * mhelio + 2.1f));
float L = Lo*(1.0f-pow(10.0f, -4.0f*r)) * common * (1e6*AU_KM);
return Vec2f(D, L);
}
QString Comet::getInfoString(const StelCore *core, const InfoStringGroup &flags) const
{
//Mostly copied from Planet::getInfoString():
QString str;
QTextStream oss(&str);
if (flags&Name)
{
oss << "<h2>";
oss << q_(englishName); // UI translation can differ from sky translation
oss.setRealNumberNotation(QTextStream::FixedNotation);
oss.setRealNumberPrecision(1);
if (sphereScale != 1.f)
oss << QString::fromUtf8(" (\xC3\x97") << sphereScale << ")";
oss << "</h2>";
}
if (flags&ObjectType)
{
if (pType.length()>0)
oss << q_("Type: <b>%1</b>").arg(q_(pType)) << "<br />";
}
if (flags&Magnitude)
{
if (core->getSkyDrawer()->getFlagHasAtmosphere())
oss << q_("Magnitude: <b>%1</b> (extincted to: <b>%2</b>)").arg(QString::number(getVMagnitude(core), 'f', 2),
QString::number(getVMagnitudeWithExtinction(core), 'f', 2)) << "<br>";
else
oss << q_("Magnitude: <b>%1</b>").arg(getVMagnitude(core), 0, 'f', 2) << "<br>";
}
if (flags&AbsoluteMagnitude)
{
//TODO: Make sure absolute magnitude is a sane value
//If the two parameter magnitude system is not use, don't display this
//value. (Using radius/albedo doesn't make any sense for comets.)
if (slopeParameter >= 0)
oss << q_("Absolute Magnitude: %1").arg(absoluteMagnitude, 0, 'f', 2) << "<br>";
}
oss << getPositionInfoString(core, flags);
if (flags&Distance)
{
// GZ: Distance from sun should be added to all planets IMHO.
double distanceAu = getHeliocentricEclipticPos().length();
double distanceKm = AU * distanceAu;
if (distanceAu < 0.1)
{
// xgettext:no-c-format
oss << QString(q_("Distance from Sun: %1AU (%2 km)"))
.arg(distanceAu, 0, 'f', 6)
.arg(distanceKm, 0, 'f', 3);
}
else
{
// xgettext:no-c-format
oss << QString(q_("Distance from Sun: %1AU (%2 Mio km)"))
.arg(distanceAu, 0, 'f', 3)
.arg(distanceKm / 1.0e6, 0, 'f', 3);
}
oss << "<br>";
distanceAu = getJ2000EquatorialPos(core).length();
distanceKm = AU * distanceAu;
if (distanceAu < 0.1)
{
// xgettext:no-c-format
oss << QString(q_("Distance: %1AU (%2 km)"))
.arg(distanceAu, 0, 'f', 6)
.arg(distanceKm, 0, 'f', 3);
}
else
{
// xgettext:no-c-format
oss << QString(q_("Distance: %1AU (%2 Mio km)"))
.arg(distanceAu, 0, 'f', 3)
.arg(distanceKm / 1.0e6, 0, 'f', 3);
}
oss << "<br>";
// GZ: Add speed. I don't know where to place that bit of information.
// xgettext:no-c-format
oss << QString(q_("Speed: %1 km/s"))
.arg(((CometOrbit*)userDataPtr)->getVelocity().length()*AU/86400.0, 0, 'f', 3);
oss << "<br>";
}
/*
if (flags&Size)
oss << q_("Apparent diameter: %1").arg(StelUtils::radToDmsStr(2.*getAngularSize(core)*M_PI/180., true));
*/
// If semi-major axis not zero then calculate and display orbital period for comet in days
double siderealPeriod = getSiderealPeriod();
if ((flags&Extra) && (siderealPeriod>0))
{
// TRANSLATORS: Sidereal (orbital) period for solar system bodies in days and in Julian years (symbol: a)
oss << q_("Sidereal period: %1 days (%2 a)").arg(QString::number(siderealPeriod, 'f', 2)).arg(QString::number(siderealPeriod/365.25, 'f', 3)) << "<br>";
}
postProcessInfoString(str, flags);
return str;
}
