4105865515

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Committed by Georg Zotti

Commit Message

Allow "goto" action to observers

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0.51

/src/core/StelCore.cpp

/*
 * Copyright (C) 2003 Fabien Chereau
 * Copyright (C) 2012 Matthew Gates
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA  02110-1335, USA.
 */

#include "StelCore.hpp"

#include "StelProjector.hpp"
#include "StelProjectorClasses.hpp"
#include "StelToneReproducer.hpp"
#include "StelApp.hpp"
#include "StelUtils.hpp"
#include "StelGeodesicGrid.hpp"
#include "StelMovementMgr.hpp"
#include "StelModuleMgr.hpp"
#include "StelPainter.hpp"
#include "StelLocationMgr.hpp"
#include "StelObserver.hpp"
#include "StelObjectMgr.hpp"
#include "Planet.hpp"
#include "SolarSystem.hpp"
#include "LandscapeMgr.hpp"
#include "StelTranslator.hpp"
#include "StelActionMgr.hpp"
#include "StelFileMgr.hpp"
#include "StelMainView.hpp"
#include "EphemWrapper.hpp"
#include "NomenclatureItem.hpp"
#include "precession.h"

#include <QSettings>
#include <QDebug>
#include <QMetaEnum>
#include <QTimeZone>
#include <QFile>
#include <QDir>
#include <QRegularExpression>
#include <QOpenGLShaderProgram>

#include <iostream>
#include <fstream>

// Init static transfo matrices
// See vsop87.doc:
const Mat4d StelCore::matJ2000ToVsop87(Mat4d::xrotation(-23.4392803055555555556*M_PI_180) * Mat4d::zrotation(0.0000275*M_PI_180));
const Mat4d StelCore::matVsop87ToJ2000(matJ2000ToVsop87.transpose());
const Mat4d StelCore::matJ2000ToGalactic(-0.054875539726, 0.494109453312, -0.867666135858, 0, -0.873437108010, -0.444829589425, -0.198076386122, 0, -0.483834985808, 0.746982251810, 0.455983795705, 0, 0, 0, 0, 1);
const Mat4d StelCore::matGalacticToJ2000(matJ2000ToGalactic.transpose());
const Mat4d StelCore::matJ2000ToSupergalactic(0.37501548, -0.89832046, 0.22887497, 0, 0.34135896, -0.09572714, -0.93504565, 0, 0.86188018, 0.42878511, 0.27075058, 0, 0, 0, 0, 1);
const Mat4d StelCore::matSupergalacticToJ2000(matJ2000ToSupergalactic.transpose());
Mat4d StelCore::matJ2000ToJ1875; // gets to be initialized in constructor.

const double StelCore::JD_SECOND = 0.000011574074074074074074;        // 1/(24*60*60)=1/86400
const double StelCore::JD_MINUTE = 0.00069444444444444444444;        // 1/(24*60)   =1/1440
const double StelCore::JD_HOUR   = 0.041666666666666666666;        // 1/24
const double StelCore::JD_DAY    = 1.;
const double StelCore::ONE_OVER_JD_SECOND = 86400;                // 86400
const double StelCore::TZ_ERA_BEGINNING = 2395996.5;                // December 1, 1847

StelCore::StelCore()
        : skyDrawer(Q_NULLPTR)
        , movementMgr(Q_NULLPTR)
        , propMgr(Q_NULLPTR)
        , geodesicGrid(Q_NULLPTR)
        , currentProjectionType(ProjectionStereographic)
        , currentDeltaTAlgorithm(EspenakMeeus)
        , position(Q_NULLPTR)
        , flagUseNutation(true)
        , flagUseAberration(true)
        , aberrationFactor(1.0)
        , flagUseTopocentricCoordinates(true)
        , timeSpeed(JD_SECOND)
        , JD(0.,0.)
        , presetSkyTime(0.)
        , milliSecondsOfLastJDUpdate(0)
        , jdOfLastJDUpdate(0.)
        , flagUseDST(true)
        , flagUseCTZ(false)
        , deltaTCustomNDot(-26.0)
        , deltaTCustomYear(1820.0)
        , deltaTnDot(-26.0)
        , deltaTdontUseMoon(false)
        , deltaTfunc(StelUtils::getDeltaTByEspenakMeeus)
        , deltaTstart(-1999)
        , deltaTfinish(3000)
        , de430Available(false)
        , de431Available(false)
        , de430Active(false)
        , de431Active(false)
        , de440Available(false)
        , de441Available(false)
        , de440Active(false)
        , de441Active(false)
{
        setObjectName("StelCore");
        registerMathMetaTypes();

        toneReproducer = new StelToneReproducer();
        milliSecondsOfLastJDUpdate = QDateTime::currentMSecsSinceEpoch();

        QSettings* conf = StelApp::getInstance().getSettings();
        // Create and initialize the default projector params
        QString tmpstr = conf->value("projection/viewport").toString();
        currentProjectorParams.maskType = StelProjector::stringToMaskType(tmpstr);
        const int viewport_width = conf->value("projection/viewport_width", currentProjectorParams.viewportXywh[2]).toInt();
        const int viewport_height = conf->value("projection/viewport_height", currentProjectorParams.viewportXywh[3]).toInt();
        const int viewport_x = conf->value("projection/viewport_x", 0).toInt();
        const int viewport_y = conf->value("projection/viewport_y", 0).toInt();
        currentProjectorParams.viewportXywh.set(viewport_x,viewport_y,viewport_width,viewport_height);

        const qreal viewportCenterX = conf->value("projection/viewport_center_x",0.5*viewport_width).toDouble();
        const qreal viewportCenterY = conf->value("projection/viewport_center_y",0.5*viewport_height).toDouble();
        currentProjectorParams.viewportCenter.set(viewportCenterX, viewportCenterY);
        const qreal viewportCenterOffsetX = conf->value("projection/viewport_center_offset_x",0.).toDouble();
        const qreal viewportCenterOffsetY = conf->value("projection/viewport_center_offset_y",0.).toDouble();
        currentProjectorParams.viewportCenterOffset.set(viewportCenterOffsetX, viewportCenterOffsetY);

        currentProjectorParams.viewportFovDiameter = conf->value("projection/viewport_fov_diameter", qMin(viewport_width,viewport_height)).toDouble();
        currentProjectorParams.flipHorz = conf->value("projection/flip_horz",false).toBool();
        currentProjectorParams.flipVert = conf->value("projection/flip_vert",false).toBool();

        currentProjectorParams.gravityLabels = conf->value("viewing/flag_gravity_labels").toBool();
        
        currentProjectorParams.devicePixelsPerPixel = StelApp::getInstance().getDevicePixelsPerPixel();

        flagUseNutation=conf->value("astro/flag_nutation", true).toBool();
        flagUseAberration=conf->value("astro/flag_aberration", true).toBool();
        aberrationFactor=conf->value("astro/aberration_factor", 1.0).toDouble();
        flagUseTopocentricCoordinates=conf->value("astro/flag_topocentric_coordinates", true).toBool();
        flagUseDST=conf->value("localization/flag_dst", true).toBool();

        // Initialize matJ2000ToJ1875 matrix
        double eps1875, chi1875, omega1875, psi1875;
        const double jdB1875 = StelUtils::getJDFromBesselianEpoch(1875.0);
        getPrecessionAnglesVondrak(jdB1875, &eps1875, &chi1875, &omega1875, &psi1875);
        matJ2000ToJ1875 = Mat4d::xrotation(84381.406*1./3600.*M_PI/180.) * Mat4d::zrotation(-psi1875) * Mat4d::xrotation(-omega1875) * Mat4d::zrotation(chi1875);
        matJ2000ToJ1875 = matJ2000ToJ1875.transpose();
}


StelCore::~StelCore()
{
        delete toneReproducer; toneReproducer=Q_NULLPTR;
        delete geodesicGrid; geodesicGrid=Q_NULLPTR;
        delete skyDrawer; skyDrawer=Q_NULLPTR;
        delete position; position=Q_NULLPTR;
}

DitheringMode StelCore::parseDitheringMode(const QString& str)
{
        const auto s=str.trimmed().toLower();
        if(s=="disabled"   ) return DitheringMode::Disabled;
        if(s=="color565"   ) return DitheringMode::Color565;
        if(s=="color666"   ) return DitheringMode::Color666;
        if(s=="color888"   ) return DitheringMode::Color888;
        if(s=="color101010") return DitheringMode::Color101010;
        return DitheringMode::Disabled;
}

/*************************************************************************
 Load core data and initialize with default values
*************************************************************************/
void StelCore::init()
{
        QSettings* conf = StelApp::getInstance().getSettings();

        const char ditheringModeKey[] = "video/dithering_mode";
        QVariant selectedDitherFormat = conf->value(ditheringModeKey);
        if(!selectedDitherFormat.isValid())
        {
                constexpr char defaultValue[] = "color888";
                selectedDitherFormat = defaultValue;
                conf->setValue(ditheringModeKey, defaultValue);
        }
        ditheringMode = parseDitheringMode(selectedDitherFormat.toString());

        if (conf->childGroups().contains("location_run_once"))
                defaultLocationID = "stellarium_cli";
        else
                defaultLocationID = conf->value("init_location/location", "auto").toString();
        bool ok;
        StelLocationMgr* locationMgr = &StelApp::getInstance().getLocationMgr();
        StelLocation location=locationMgr->getLastResortLocation(); // first location: Paris. Required if no IP connection on first launch!
        if (defaultLocationID == "auto")
        {
                locationMgr->locationFromIP();
        }
        else if (defaultLocationID == "stellarium_cli")
        {
                location = locationMgr->locationFromCLI();
        }
        else if (defaultLocationID.startsWith("GPS", Qt::CaseInsensitive))
        {
                // The location is obtained already from init_location/last_resort_location
                location.name = conf->value("init_location/location").toString();
        }
        else
        {
                location = locationMgr->locationForString(defaultLocationID);
        }

        if (!location.isValid())
        {
                qWarning() << "Warning: location" << defaultLocationID << "is unknown.";
                location = locationMgr->getLastResortLocation();
        }
        position = new StelObserver(location);

        QString ctz = conf->value("localization/time_zone", "").toString();
        if (!ctz.isEmpty())
                setUseCustomTimeZone(true);
        else
                ctz = getCurrentLocation().ianaTimeZone;
        setCurrentTimeZone(ctz);

        // Delta-T stuff
        // Define default algorithm for time correction (Delta T)
        QString tmpDT = conf->value("navigation/time_correction_algorithm", "EspenakMeeusModified").toString();
        setCurrentDeltaTAlgorithmKey(tmpDT);

        // Define variables of custom equation for calculation of Delta T
        // Default: ndot = -26.0 "/cy/cy; year = 1820; DeltaT = -20 + 32*u^2, where u = (currentYear-1820)/100
        setDeltaTCustomYear(conf->value("custom_time_correction/year", 1820.0).toDouble());
        setDeltaTCustomNDot(conf->value("custom_time_correction/ndot", -26.0).toDouble());
        setDeltaTCustomEquationCoefficients(Vec3d(conf->value("custom_time_correction/coefficients", "-20,0,32").toString()));

        // Time stuff
        setTimeNow();

        // We want to be able to handle the old style preset time, recorded as a double
        // jday, or as a more human readable string...
        QString presetTimeStr = conf->value("navigation/preset_sky_time",2451545.).toString();
        presetSkyTime = presetTimeStr.toDouble(&ok);
        if (ok)
        {
                qDebug() << "navigation/preset_sky_time is a double - treating as jday:" << QString::number(presetSkyTime, 'f', 5);
        }
        else
        {
                qDebug() << "navigation/preset_sky_time was not a double, treating as string date:" << presetTimeStr;
                presetSkyTime = StelUtils::qDateTimeToJd(QDateTime::fromString(presetTimeStr));
        }
        setInitTodayTime(QTime::fromString(conf->value("navigation/today_time", "22:00").toString()));
        startupTimeMode = conf->value("navigation/startup_time_mode", "actual").toString().toLower();
        if (startupTimeMode=="preset")        
                setJD(presetSkyTime - static_cast<double>(getUTCOffset(presetSkyTime)) * JD_HOUR);
        else if (startupTimeMode=="today")
                setTodayTime(getInitTodayTime());

        // Compute transform matrices between coordinates systems
        updateTransformMatrices();
        updateFixedEquatorialTransformMatrices();
        connect(this, SIGNAL(locationChanged(const StelLocation&)), this, SLOT(updateFixedEquatorialTransformMatrices()));

        movementMgr = new StelMovementMgr(this);
        movementMgr->init();
        currentProjectorParams.fov = static_cast<float>(movementMgr->getInitFov());
        StelApp::getInstance().getModuleMgr().registerModule(movementMgr);

        skyDrawer = new StelSkyDrawer(this);
        skyDrawer->init();

        propMgr = StelApp::getInstance().getStelPropertyManager();
        propMgr->registerObject(skyDrawer);
        propMgr->registerObject(this);
        propMgr->registerObject(toneReproducer);

        setCurrentProjectionTypeKey(getDefaultProjectionTypeKey());
        updateMaximumFov();

        // activate DE430/431
        initEphemeridesFunctions();

        // Register all the core actions.
        QString timeGroup = N_("Date and Time");
        QString movementGroup = N_("Movement and Selection");
        QString displayGroup = N_("Display Options");
        StelActionMgr* actionsMgr = StelApp::getInstance().getStelActionManager();
        actionsMgr->addAction("actionIncrease_Time_Speed", timeGroup, N_("Increase time speed"), this, "increaseTimeSpeed()", "L");
        actionsMgr->addAction("actionDecrease_Time_Speed", timeGroup, N_("Decrease time speed"), this, "decreaseTimeSpeed()", "J");
        actionsMgr->addAction("actionIncrease_Time_Speed_Less", timeGroup, N_("Increase time speed (a little)"), this, "increaseTimeSpeedLess()", "Shift+L");
        actionsMgr->addAction("actionDecrease_Time_Speed_Less", timeGroup, N_("Decrease time speed (a little)"), this, "decreaseTimeSpeedLess()", "Shift+J");
        actionsMgr->addAction("actionSet_Real_Time_Speed", timeGroup, N_("Set normal time rate"), this, "toggleRealTimeSpeed()", "K");
        actionsMgr->addAction("actionSet_Time_Rate_Zero", timeGroup, N_("Set time rate to zero"), this, "setZeroTimeSpeed()", "7");
        actionsMgr->addAction("actionSet_Time_Reverse", timeGroup, N_("Set reverse time direction"), this, "revertTimeDirection()", "0");
        actionsMgr->addAction("actionReturn_To_Current_Time", timeGroup, N_("Set time to now"), this, "setTimeNow()", "8");
        actionsMgr->addAction("actionAdd_Solar_Minute", timeGroup, N_("Add 1 solar minute"), this, "addMinute()");
        actionsMgr->addAction("actionAdd_Solar_Hour", timeGroup, N_("Add 1 solar hour"), this, "addHour()", "Ctrl+=");
        actionsMgr->addAction("actionAdd_Solar_Day", timeGroup, N_("Add 1 solar day"), this, "addDay()", "=");
        actionsMgr->addAction("actionAdd_Solar_Week", timeGroup, N_("Add 7 solar days"), this, "addWeek()", "]");
        actionsMgr->addAction("actionSubtract_Solar_Minute", timeGroup, N_("Subtract 1 solar minute"), this, "subtractMinute()");
        actionsMgr->addAction("actionSubtract_Solar_Hour", timeGroup, N_("Subtract 1 solar hour"), this, "subtractHour()", "Ctrl+-");
        actionsMgr->addAction("actionSubtract_Solar_Day", timeGroup, N_("Subtract 1 solar day"), this, "subtractDay()", "-");
        actionsMgr->addAction("actionSubtract_Solar_Week", timeGroup, N_("Subtract 7 solar days"), this, "subtractWeek()", "[");
        actionsMgr->addAction("actionAdd_Sidereal_Day", timeGroup, N_("Add 1 sidereal day"), this, "addSiderealDay()", "Alt+=");
        actionsMgr->addAction("actionAdd_Sidereal_Week", timeGroup, N_("Add 7 sidereal days"), this, "addSiderealWeek()");
        actionsMgr->addAction("actionAdd_Sidereal_Year", timeGroup, N_("Add 1 sidereal year"), this, "addSiderealYear()", "Ctrl+Alt+Shift+]");
        actionsMgr->addAction("actionAdd_Sidereal_Century", timeGroup, N_("Add 100 sidereal years"), this, "addSiderealYears()");
        actionsMgr->addAction("actionAdd_Synodic_Month", timeGroup, N_("Add 1 synodic month"), this, "addSynodicMonth()");
        actionsMgr->addAction("actionAdd_Saros", timeGroup, N_("Add 1 saros"), this, "addSaros()");
        actionsMgr->addAction("actionAdd_Draconic_Month", timeGroup, N_("Add 1 draconic month"), this, "addDraconicMonth()");
        actionsMgr->addAction("actionAdd_Draconic_Year", timeGroup, N_("Add 1 draconic year"), this, "addDraconicYear()");
        actionsMgr->addAction("actionAdd_Anomalistic_Month", timeGroup, N_("Add 1 anomalistic month"), this, "addAnomalisticMonth()");
        actionsMgr->addAction("actionAdd_Anomalistic_Year", timeGroup, N_("Add 1 anomalistic year"), this, "addAnomalisticYear()");
        actionsMgr->addAction("actionAdd_Anomalistic_Century", timeGroup, N_("Add 100 anomalistic years"), this, "addAnomalisticYears()");
        actionsMgr->addAction("actionAdd_Mean_Tropical_Month", timeGroup, N_("Add 1 mean tropical month"), this, "addMeanTropicalMonth()");
        actionsMgr->addAction("actionAdd_Mean_Tropical_Year", timeGroup, N_("Add 1 mean tropical year"), this, "addMeanTropicalYear()");
        actionsMgr->addAction("actionAdd_Mean_Tropical_Century", timeGroup, N_("Add 100 mean tropical years"), this, "addMeanTropicalYears()");
        actionsMgr->addAction("actionAdd_Tropical_Year", timeGroup, N_("Add 1 tropical year"), this, "addTropicalYear()");
        actionsMgr->addAction("actionAdd_Julian_Year", timeGroup, N_("Add 1 Julian year"), this, "addJulianYear()");
        actionsMgr->addAction("actionAdd_Julian_Century", timeGroup, N_("Add 1 Julian century"), this, "addJulianYears()");
        actionsMgr->addAction("actionAdd_Gaussian_Year", timeGroup, N_("Add 1 Gaussian year"), this, "addGaussianYear()");
        actionsMgr->addAction("actionAdd_Calendric_Month", timeGroup, N_("Add 1 calendric month"), this, "addCalendricMonth()");
        actionsMgr->addAction("actionSubtract_Sidereal_Day", timeGroup, N_("Subtract 1 sidereal day"), this, "subtractSiderealDay()", "Alt+-");
        actionsMgr->addAction("actionSubtract_Sidereal_Week", timeGroup, N_("Subtract 7 sidereal days"), this, "subtractSiderealWeek()");
        actionsMgr->addAction("actionSubtract_Sidereal_Year", timeGroup, N_("Subtract 1 sidereal year"), this, "subtractSiderealYear()", "Ctrl+Alt+Shift+[");
        actionsMgr->addAction("actionSubtract_Sidereal_Century", timeGroup, N_("Subtract 100 sidereal years"), this, "subtractSiderealYears()");
        actionsMgr->addAction("actionSubtract_Synodic_Month", timeGroup, N_("Subtract 1 synodic month"), this, "subtractSynodicMonth()");
        actionsMgr->addAction("actionSubtract_Saros", timeGroup, N_("Subtract 1 saros"), this, "subtractSaros()");
        actionsMgr->addAction("actionSubtract_Draconic_Month", timeGroup, N_("Subtract 1 draconic month"), this, "subtractDraconicMonth()");
        actionsMgr->addAction("actionSubtract_Draconic_Year", timeGroup, N_("Subtract 1 draconic year"), this, "subtractDraconicYear()");
        actionsMgr->addAction("actionSubtract_Anomalistic_Month", timeGroup, N_("Subtract 1 anomalistic month"), this, "subtractAnomalisticMonth()");
        actionsMgr->addAction("actionSubtract_Anomalistic_Year", timeGroup, N_("Subtract 1 anomalistic year"), this, "subtractAnomalisticYear()");
        actionsMgr->addAction("actionSubtract_Anomalistic_Century", timeGroup, N_("Subtract 100 anomalistic years"), this, "subtractAnomalisticYears()");
        actionsMgr->addAction("actionSubtract_Mean_Tropical_Month", timeGroup, N_("Subtract 1 mean tropical month"), this, "subtractMeanTropicalMonth()");
        actionsMgr->addAction("actionSubtract_Mean_Tropical_Year", timeGroup, N_("Subtract 1 mean tropical year"), this, "subtractMeanTropicalYear()");
        actionsMgr->addAction("actionSubtract_Mean_Tropical_Century", timeGroup, N_("Subtract 100 mean tropical years"), this, "subtractMeanTropicalYears()");
        actionsMgr->addAction("actionSubtract_Tropical_Year", timeGroup, N_("Subtract 1 tropical year"), this, "subtractTropicalYear()");
        actionsMgr->addAction("actionSubtract_Julian_Year", timeGroup, N_("Subtract 1 Julian year"), this, "subtractJulianYear()");
        actionsMgr->addAction("actionSubtract_Julian_Century", timeGroup, N_("Subtract 1 Julian century"), this, "subtractJulianYears()");
        actionsMgr->addAction("actionSubtract_Gaussian_Year", timeGroup, N_("Subtract 1 Gaussian year"), this, "subtractGaussianYear()");
        actionsMgr->addAction("actionSubtract_Calendric_Month", timeGroup, N_("Subtract 1 calendric month"), this, "subtractCalendricMonth()");

        actionsMgr->addAction("actionSet_Home_Planet_To_Selected", movementGroup, N_("Set home planet to selected planet"), this, "moveObserverToSelected()", "Ctrl+G");
        actionsMgr->addAction("actionGo_Home_Global", movementGroup, N_("Go to home"), this, "returnToHome()", "Ctrl+H");

        actionsMgr->addAction("actionHorizontal_Flip", displayGroup, N_("Flip scene horizontally"), this, "flipHorz", "Ctrl+Shift+H", "", true);
        actionsMgr->addAction("actionVertical_Flip", displayGroup, N_("Flip scene vertically"), this, "flipVert", "Ctrl+Shift+V", "", true);
}

QString StelCore::getDefaultProjectionTypeKey() const
{
        QSettings* conf = StelApp::getInstance().getSettings();
        return conf->value("projection/type", "ProjectionStereographic").toString();
}

// Get the shared instance of StelGeodesicGrid.
// The returned instance is guaranteed to allow for at least maxLevel levels
const StelGeodesicGrid* StelCore::getGeodesicGrid(int maxLevel) const
{
        if (geodesicGrid==Q_NULLPTR)
        {
                geodesicGrid = new StelGeodesicGrid(maxLevel);
        }
        else if (maxLevel>geodesicGrid->getMaxLevel())
        {
                delete geodesicGrid;
                geodesicGrid = new StelGeodesicGrid(maxLevel);
        }
        return geodesicGrid;
}

StelProjectorP StelCore::getProjection2d() const
{
        StelProjectorP prj(new StelProjector2d());
        prj->init(currentProjectorParams);
        return prj;
}

StelProjectorP StelCore::getProjection(StelProjector::ModelViewTranformP modelViewTransform, ProjectionType projType) const
{
        if (projType==static_cast<ProjectionType>(1000))
                projType = currentProjectionType;

        StelProjectorP prj;
        switch (projType)
        {
                case ProjectionPerspective:
                        prj = StelProjectorP(new StelProjectorPerspective(modelViewTransform));
                        break;
                case ProjectionEqualArea:
                        prj = StelProjectorP(new StelProjectorEqualArea(modelViewTransform));
                        break;
                case ProjectionStereographic:
                        prj = StelProjectorP(new StelProjectorStereographic(modelViewTransform));
                        break;
                case ProjectionFisheye:
                        prj = StelProjectorP(new StelProjectorFisheye(modelViewTransform));
                        break;
                case ProjectionHammer:
                        prj = StelProjectorP(new StelProjectorHammer(modelViewTransform));
                        break;
                case ProjectionCylinder:
                        prj = StelProjectorP(new StelProjectorCylinder(modelViewTransform));
                        break;
                case ProjectionCylinderFill:
                        prj = StelProjectorP(new StelProjectorCylinderFill(modelViewTransform));
                        break;
                case ProjectionMercator:
                        prj = StelProjectorP(new StelProjectorMercator(modelViewTransform));
                        break;
                case ProjectionOrthographic:
                        prj = StelProjectorP(new StelProjectorOrthographic(modelViewTransform));
                        break;
                case ProjectionSinusoidal:
                        prj = StelProjectorP(new StelProjectorSinusoidal(modelViewTransform));
                        break;
                case ProjectionMiller:
                        prj = StelProjectorP(new StelProjectorMiller(modelViewTransform));
                        break;
                default:
                        qWarning() << "Unknown projection type: " << static_cast<int>(projType) << "using ProjectionStereographic instead";
                        prj = StelProjectorP(new StelProjectorStereographic(modelViewTransform));
                        Q_ASSERT(0);
        }
        prj->init(currentProjectorParams);
        return prj;
}

// Get an instance of projector using the current display parameters from Navigation, StelMovementMgr
StelProjectorP StelCore::getProjection(FrameType frameType, RefractionMode refractionMode) const
{
        switch (frameType)
        {
                case FrameAltAz:
                        return getProjection(getAltAzModelViewTransform(refractionMode));
                case FrameHeliocentricEclipticJ2000:
                        return getProjection(getHeliocentricEclipticModelViewTransform(refractionMode));
                case FrameObservercentricEclipticJ2000:
                        return getProjection(getObservercentricEclipticJ2000ModelViewTransform(refractionMode));
                case FrameObservercentricEclipticOfDate:
                        return getProjection(getObservercentricEclipticOfDateModelViewTransform(refractionMode));
                case FrameEquinoxEqu:
                        return getProjection(getEquinoxEquModelViewTransform(refractionMode));
                case FrameFixedEquatorial:
                        return getProjection(getFixedEquatorialModelViewTransform(refractionMode));
                case FrameJ2000:
                        return getProjection(getJ2000ModelViewTransform(refractionMode));
                case FrameGalactic:
                        return getProjection(getGalacticModelViewTransform(refractionMode));
                case FrameSupergalactic:
                        return getProjection(getSupergalacticModelViewTransform(refractionMode));
                default:
                        qDebug() << "Unknown reference frame type: " << static_cast<int>(frameType) << ".";
        }
        Q_ASSERT(0);
        return getProjection2d();
}

SphericalCap StelCore::getVisibleSkyArea() const
{
        const LandscapeMgr* landscapeMgr = GETSTELMODULE(LandscapeMgr);
        Vec3d up(0, 0, 1);
        up = altAzToJ2000(up, RefractionOff);
        
        // Limit star drawing to above landscape's minimal altitude (was const=-0.035, Bug lp:1469407)
        if (landscapeMgr->getIsLandscapeFullyVisible())
        {
                return SphericalCap(up, landscapeMgr->getLandscapeSinMinAltitudeLimit());
        }
        return SphericalCap(up, -1.);
}

// Handle the resizing of the window
void StelCore::windowHasBeenResized(qreal x, qreal y, qreal width, qreal height)
{
        // Maximize display when resized since it invalidates previous options anyway
        currentProjectorParams.viewportXywh.set(qRound(x), qRound(y), qRound(width), qRound(height));
        currentProjectorParams.viewportCenter.set(x+(0.5+currentProjectorParams.viewportCenterOffset.v[0])*width, y+(0.5+currentProjectorParams.viewportCenterOffset.v[1])*height);
        currentProjectorParams.viewportFovDiameter = qMin(width,height);

        if (currentProjectionType==ProjectionType::ProjectionCylinderFill)
        {
                currentProjectorParams.widthStretch=0.5*width/height;
                currentProjectorParams.viewportFovDiameter = height;
        }
}

/*************************************************************************
 Update all the objects in function of the time
*************************************************************************/
void StelCore::update(double deltaTime)
{
        // Update the position of observation and time and recompute planet positions etc...
        updateTime(deltaTime);

        // Transform matrices between coordinates systems
        updateTransformMatrices();

        // Update direction of vision/Zoom level
        movementMgr->updateMotion(deltaTime);

        currentProjectorParams.fov = static_cast<float>(movementMgr->getCurrentFov());

        skyDrawer->update(deltaTime);
}


/*************************************************************************
 Execute all the pre-drawing functions
*************************************************************************/
void StelCore::preDraw()
{
        // Init openGL viewing with fov, screen size and clip planes
        currentProjectorParams.zNear = 0.000001;
        currentProjectorParams.zFar = 500.;

        // Clear the render buffer.
        // Here we can set a sky background color if really wanted (art
        // applications. Astronomical sky should be 0/0/0/0)
        Vec3f backColor = StelMainView::getInstance().getSkyBackgroundColor();
        QOpenGLFunctions* gl = QOpenGLContext::currentContext()->functions();
        gl->glClearColor(backColor[0], backColor[1], backColor[2], 0.f);
        gl->glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);

        skyDrawer->preDraw();
}


/*************************************************************************
 Update core state after drawing modules
*************************************************************************/
void StelCore::postDraw()
{
        StelPainter sPainter(getProjection(StelCore::FrameJ2000));
        sPainter.drawViewportShape();
}

void StelCore::updateMaximumFov()
{
        const float savedFov = currentProjectorParams.fov;
        currentProjectorParams.fov = 0.0001f;        // Avoid crash
        const float newMaxFov = getProjection(StelProjector::ModelViewTranformP(new StelProjector::Mat4dTransform(Mat4d::identity(),Mat4d::identity())))->getMaxFov();
        movementMgr->setMaxFov(static_cast<double>(newMaxFov));
        currentProjectorParams.fov = qMin(newMaxFov, savedFov);
}

void StelCore::setCurrentProjectionType(ProjectionType type)
{
        if(type!=currentProjectionType)
        {
                QSettings* conf = StelApp::getInstance().getSettings();

                currentProjectionType=type;
                updateMaximumFov();
                if (currentProjectionType==ProjectionType::ProjectionCylinderFill)
                {
                        // Save whatever stretch is present into config.ini. This value is saved just temporarily until switching back to another projection and will not be loaded on startup.
                        // (To configure a stretch at startup, use startup.ssc script.)
                        conf->setValue("projection/width_stretch", currentProjectorParams.widthStretch);
                        currentProjectorParams.fov=180.f;
                        currentProjectorParams.widthStretch=0.5*currentProjectorParams.viewportXywh[2]/currentProjectorParams.viewportXywh[3];
                        currentProjectorParams.viewportFovDiameter = currentProjectorParams.viewportXywh[3];
                        Q_ASSERT(movementMgr);
                        movementMgr->setViewportVerticalOffsetTarget(0.);
                        movementMgr->zoomTo(180., 0.5);
                }
                else
                {
                        // reset to what is stored in config.ini
                        currentProjectorParams.widthStretch=conf->value("projection/width_stretch", 1.0).toDouble();
                }

                emit currentProjectionTypeChanged(type);
                emit currentProjectionTypeKeyChanged(getCurrentProjectionTypeKey());
                emit currentProjectionNameI18nChanged(getCurrentProjectionNameI18n());
        }
}

StelCore::ProjectionType StelCore::getCurrentProjectionType() const
{
        return currentProjectionType;
}

//! Set the current projection type to use
void StelCore::setCurrentProjectionTypeKey(QString key)
{
        const QMetaEnum& en = metaObject()->enumerator(metaObject()->indexOfEnumerator("ProjectionType"));
        ProjectionType newType = static_cast<ProjectionType>(en.keyToValue(key.toLatin1().data()));
        if (newType<0)
        {
                qWarning() << "Unknown projection type: " << key << "setting \"ProjectionStereographic\" instead";
                newType = ProjectionStereographic;
        }
        setCurrentProjectionType(newType);
}

//! Get the current Mapping used by the Projection
QString StelCore::getCurrentProjectionTypeKey(void) const
{
        return metaObject()->enumerator(metaObject()->indexOfEnumerator("ProjectionType")).key(currentProjectionType);
}

QString StelCore::getCurrentProjectionNameI18n() const
{
        return projectionTypeKeyToNameI18n(getCurrentProjectionTypeKey());
}

//! Get the list of all the available projections
QStringList StelCore::getAllProjectionTypeKeys() const
{
        const QMetaEnum& en = metaObject()->enumerator(metaObject()->indexOfEnumerator("ProjectionType"));
        QStringList l;
        for (int i=0;i<en.keyCount();++i)
                l << en.key(i);
        return l;
}

void StelCore::setMaskType(StelProjector::StelProjectorMaskType m)
{
        currentProjectorParams.maskType = m;
}

void StelCore::setFlagGravityLabels(bool gravity)
{
        currentProjectorParams.gravityLabels = gravity;
        emit flagGravityLabelsChanged(gravity);
}

bool StelCore::getFlagGravityLabels() const
{
        return currentProjectorParams.gravityLabels;
}

void StelCore::setDefaultAngleForGravityText(float a)
{
        currentProjectorParams.defaultAngleForGravityText = a;
}

void StelCore::setFlipHorz(bool flip)
{
        if (currentProjectorParams.flipHorz != flip)
        {
                currentProjectorParams.flipHorz = flip;
                emit flipHorzChanged(flip);
        }
}

void StelCore::setFlipVert(bool flip)
{
        if (currentProjectorParams.flipVert != flip)
        {
                currentProjectorParams.flipVert = flip;
                emit flipVertChanged(flip);
        }
}

bool StelCore::getFlipHorz(void) const
{
        return currentProjectorParams.flipHorz;
}

bool StelCore::getFlipVert(void) const
{
        return currentProjectorParams.flipVert;
}

// Get current value for horizontal viewport offset [-50...50]
double StelCore::getViewportHorizontalOffset(void) const
{
        return (currentProjectorParams.viewportCenterOffset[0] * 100.0);
}
// Set horizontal viewport offset. Argument will be clamped to be inside [-50...50]
void StelCore::setViewportHorizontalOffset(double newOffsetPct)
{
        currentProjectorParams.viewportCenterOffset[0]=0.01* qBound(-50., newOffsetPct, 50.);
        currentProjectorParams.viewportCenter.set(currentProjectorParams.viewportXywh[0]+(0.5+currentProjectorParams.viewportCenterOffset.v[0])*currentProjectorParams.viewportXywh[2],
                                                currentProjectorParams.viewportXywh[1]+(0.5+currentProjectorParams.viewportCenterOffset.v[1])*currentProjectorParams.viewportXywh[3]);
}

// Get current value for vertical viewport offset [-50...50]
double StelCore::getViewportVerticalOffset(void) const
{
        return (currentProjectorParams.viewportCenterOffset[1] * 100.0);
}
// Set vertical viewport offset. Argument will be clamped to be inside [-50...50]
void StelCore::setViewportVerticalOffset(double newOffsetPct)
{
        currentProjectorParams.viewportCenterOffset[1]=0.01* qBound(-50., newOffsetPct, 50.);
        currentProjectorParams.viewportCenter.set(currentProjectorParams.viewportXywh[0]+(0.5+currentProjectorParams.viewportCenterOffset.v[0])*currentProjectorParams.viewportXywh[2],
                                                currentProjectorParams.viewportXywh[1]+(0.5+currentProjectorParams.viewportCenterOffset.v[1])*currentProjectorParams.viewportXywh[3]);
}

// Set both viewport offsets. Arguments will be clamped to be inside [-50...50]. I (GZ) hope this will avoid some of the shaking.
void StelCore::setViewportOffset(double newHorizontalOffsetPct, double newVerticalOffsetPct)
{
        currentProjectorParams.viewportCenterOffset[0]=0.01* qBound(-50., newHorizontalOffsetPct, 50.);
        currentProjectorParams.viewportCenterOffset[1]=0.01* qBound(-50., newVerticalOffsetPct,   50.);
        currentProjectorParams.viewportCenter.set(currentProjectorParams.viewportXywh[0]+(0.5+currentProjectorParams.viewportCenterOffset.v[0])*currentProjectorParams.viewportXywh[2],
                                                currentProjectorParams.viewportXywh[1]+(0.5+currentProjectorParams.viewportCenterOffset.v[1])*currentProjectorParams.viewportXywh[3]);
}

void StelCore::setViewportStretch(float stretch)
{
        currentProjectorParams.widthStretch=static_cast<qreal>(qMax(0.001f, stretch));
}

QString StelCore::getDefaultLocationID() const
{
        return defaultLocationID;
}

QString StelCore::projectionTypeKeyToNameI18n(const QString& key) const
{
        const QMetaEnum& en = metaObject()->enumerator(metaObject()->indexOfEnumerator("ProjectionType"));
        QString s(getProjection(StelProjector::ModelViewTranformP(new StelProjector::Mat4dTransform(Mat4d::identity(),Mat4d::identity())), static_cast<ProjectionType>(en.keyToValue(key.toLatin1())))->getNameI18());
        return s;
}

QString StelCore::projectionNameI18nToTypeKey(const QString& nameI18n) const
{
        const QMetaEnum& en = metaObject()->enumerator(metaObject()->indexOfEnumerator("ProjectionType"));
        for (int i=0;i<en.keyCount();++i)
        {
                if (getProjection(StelProjector::ModelViewTranformP(new StelProjector::Mat4dTransform(Mat4d::identity(),Mat4d::identity())), static_cast<ProjectionType>(i))->getNameI18()==nameI18n)
                        return en.valueToKey(i);
        }
        // Unknown translated name
        Q_ASSERT(0);
        return en.valueToKey(ProjectionStereographic);
}

StelProjector::StelProjectorParams StelCore::getCurrentStelProjectorParams() const
{
        return currentProjectorParams;
}

void StelCore::setCurrentStelProjectorParams(const StelProjector::StelProjectorParams& newParams)
{
        currentProjectorParams=newParams;
}

void StelCore::lookAtJ2000(const Vec3d& pos, const Vec3d& aup)
{
        Vec3d f(j2000ToAltAz(pos, RefractionOff));
        Vec3d up(j2000ToAltAz(aup, RefractionOff));
        f.normalize();
        up.normalize();

        // Update the model view matrix
        Vec3d s(f^up);        // y vector
        s.normalize();
        Vec3d u(s^f);        // Up vector in AltAz coordinates
        u.normalize();
        matAltAzModelView.set(s[0],u[0],-f[0],0.,
                              s[1],u[1],-f[1],0.,
                              s[2],u[2],-f[2],0.,
                              0.,0.,0.,1.);
        invertMatAltAzModelView = matAltAzModelView.inverse();
}

void StelCore::setMatAltAzModelView(const Mat4d& mat)
{
        matAltAzModelView = mat;
        invertMatAltAzModelView = matAltAzModelView.inverse();
}

Vec3d StelCore::altAzToEquinoxEqu(const Vec3d& v, RefractionMode refMode) const
{
        if (refMode==RefractionOff || skyDrawer==Q_NULLPTR || (refMode==RefractionAuto && skyDrawer->getFlagHasAtmosphere()==false))
                return matAltAzToEquinoxEqu*v;
        Vec3d r(v);
        skyDrawer->getRefraction().backward(r);
        r.transfo4d(matAltAzToEquinoxEqu);
        return r;
}

Vec3d StelCore::equinoxEquToAltAz(const Vec3d& v, RefractionMode refMode) const
{
        if (refMode==RefractionOff || skyDrawer==Q_NULLPTR || (refMode==RefractionAuto && skyDrawer->getFlagHasAtmosphere()==false))
                return matEquinoxEquToAltAz*v;
        Vec3d r(v);
        r.transfo4d(matEquinoxEquToAltAz);
        skyDrawer->getRefraction().forward(r);
        return r;
}

Vec3d StelCore::altAzToJ2000(const Vec3d& v, RefractionMode refMode) const
{
        if (refMode==RefractionOff || skyDrawer==Q_NULLPTR || (refMode==RefractionAuto && skyDrawer->getFlagHasAtmosphere()==false))
                return matEquinoxEquDateToJ2000*matAltAzToEquinoxEqu*v;
        Vec3d r(v);
        skyDrawer->getRefraction().backward(r);
        r.transfo4d(matEquinoxEquDateToJ2000*matAltAzToEquinoxEqu);
        return r;
}

Vec3d StelCore::j2000ToAltAz(const Vec3d& v, RefractionMode refMode) const
{
        if (refMode==RefractionOff || skyDrawer==Q_NULLPTR || (refMode==RefractionAuto && skyDrawer->getFlagHasAtmosphere()==false))
                return matJ2000ToAltAz*v;
        Vec3d r(v);
        r.transfo4d(matJ2000ToAltAz);
        skyDrawer->getRefraction().forward(r);
        return r;
}

Vec3d StelCore::galacticToJ2000(const Vec3d& v) const
{
        return matGalacticToJ2000*v;
}

Vec3d StelCore::supergalacticToJ2000(const Vec3d& v) const
{
        return matSupergalacticToJ2000*v;
}

Vec3d StelCore::equinoxEquToJ2000(const Vec3d& v, RefractionMode refMode) const
{
        if (refMode==RefractionOff || skyDrawer==Q_NULLPTR || (refMode==RefractionAuto && skyDrawer->getFlagHasAtmosphere()==false))
                return matEquinoxEquDateToJ2000*v;
        Vec3d r(v);
        r.transfo4d(matEquinoxEquToAltAz);
        skyDrawer->getRefraction().backward(r);
        r.transfo4d(matAltAzToJ2000);
        return r;
}

Vec3d StelCore::j2000ToEquinoxEqu(const Vec3d& v, RefractionMode refMode) const
{
        if (refMode==RefractionOff || skyDrawer==Q_NULLPTR || (refMode==RefractionAuto && skyDrawer->getFlagHasAtmosphere()==false))
                return matJ2000ToEquinoxEqu*v;
        Vec3d r(v);
        r.transfo4d(matJ2000ToAltAz);
        skyDrawer->getRefraction().forward(r);
        r.transfo4d(matAltAzToEquinoxEqu);
        return r;
}

Vec3d StelCore::j2000ToJ1875(const Vec3d& v) const
{
        return matJ2000ToJ1875*v;
}

Vec3d StelCore::j2000ToGalactic(const Vec3d& v) const
{
        return matJ2000ToGalactic*v;
}

Vec3d StelCore::j2000ToSupergalactic(const Vec3d& v) const
{
        return matJ2000ToSupergalactic*v;
}

//! Transform vector from heliocentric ecliptic coordinate to altazimuthal
Vec3d StelCore::heliocentricEclipticToAltAz(const Vec3d& v, RefractionMode refMode) const
{
        if (refMode==RefractionOff || skyDrawer==Q_NULLPTR || (refMode==RefractionAuto && skyDrawer->getFlagHasAtmosphere()==false))
                return matHeliocentricEclipticJ2000ToAltAz*v;
        Vec3d r(v);
        r.transfo4d(matHeliocentricEclipticJ2000ToAltAz);
        skyDrawer->getRefraction().forward(r);
        return r;
}

//! Transform from heliocentric coordinate to equatorial at current equinox (for the planet where the observer stands)
Vec3d StelCore::heliocentricEclipticToEquinoxEqu(const Vec3d& v) const
{
        return matHeliocentricEclipticToEquinoxEqu*v;
}

/*
//! Transform vector from heliocentric coordinate to false equatorial : equatorial
//! coordinate but centered on the observer position (useful for objects close to earth)
//! Unused as of V0.13
Vec3d StelCore::heliocentricEclipticToEarthPosEquinoxEqu(const Vec3d& v) const
{
        return matAltAzToEquinoxEqu*matHeliocentricEclipticToAltAz*v;
}
*/

StelProjector::ModelViewTranformP StelCore::getHeliocentricEclipticModelViewTransform(RefractionMode refMode) const
{
        if (refMode==RefractionOff || skyDrawer==Q_NULLPTR || (refMode==RefractionAuto && skyDrawer->getFlagHasAtmosphere()==false))
                return StelProjector::ModelViewTranformP(new StelProjector::Mat4dTransform(matAltAzModelView,matHeliocentricEclipticJ2000ToAltAz));
        Refraction* refr = new Refraction(skyDrawer->getRefraction());
        // The pretransform matrix will convert from input coordinates to AltAz needed by the refraction function.
        refr->setPreTransfoMat(matHeliocentricEclipticJ2000ToAltAz);
        refr->setPostTransfoMat(matAltAzModelView);
        return StelProjector::ModelViewTranformP(refr);
}

//! Get the modelview matrix for observer-centric ecliptic J2000 (Vsop87A) drawing
StelProjector::ModelViewTranformP StelCore::getObservercentricEclipticJ2000ModelViewTransform(RefractionMode refMode) const
{
        if (refMode==RefractionOff || skyDrawer==Q_NULLPTR || (refMode==RefractionAuto && skyDrawer->getFlagHasAtmosphere()==false))
                return StelProjector::ModelViewTranformP(new StelProjector::Mat4dTransform(matAltAzModelView,matJ2000ToAltAz*matVsop87ToJ2000));
        Refraction* refr = new Refraction(skyDrawer->getRefraction());
        // The pretransform matrix will convert from input coordinates to AltAz needed by the refraction function.
        refr->setPreTransfoMat(matJ2000ToAltAz*matVsop87ToJ2000);
        refr->setPostTransfoMat(matAltAzModelView);
        return StelProjector::ModelViewTranformP(refr);
}

//! Get the modelview matrix for observer-centric ecliptic-of-date drawing
StelProjector::ModelViewTranformP StelCore::getObservercentricEclipticOfDateModelViewTransform(RefractionMode refMode) const
{
        double eps_A=getPrecessionAngleVondrakCurrentEpsilonA();
        if (refMode==RefractionOff || skyDrawer==Q_NULLPTR || (refMode==RefractionAuto && skyDrawer->getFlagHasAtmosphere()==false))
                return StelProjector::ModelViewTranformP(new StelProjector::Mat4dTransform(matAltAzModelView,matEquinoxEquToAltAz* Mat4d::xrotation(eps_A)));
        Refraction* refr = new Refraction(skyDrawer->getRefraction());
        // The pretransform matrix will convert from input coordinates to AltAz needed by the refraction function.
        refr->setPreTransfoMat(matEquinoxEquToAltAz* Mat4d::xrotation(eps_A));
        refr->setPostTransfoMat(matAltAzModelView);
        return StelProjector::ModelViewTranformP(refr);
}

//! Get the modelview matrix for observer-centric equatorial at equinox drawing
StelProjector::ModelViewTranformP StelCore::getEquinoxEquModelViewTransform(RefractionMode refMode) const
{
        if (refMode==RefractionOff || skyDrawer==Q_NULLPTR || (refMode==RefractionAuto && skyDrawer->getFlagHasAtmosphere()==false))
                return StelProjector::ModelViewTranformP(new StelProjector::Mat4dTransform(matAltAzModelView,matEquinoxEquToAltAz));
        Refraction* refr = new Refraction(skyDrawer->getRefraction());
        // The pretransform matrix will convert from input coordinates to AltAz needed by the refraction function.
        refr->setPreTransfoMat(matEquinoxEquToAltAz);
        refr->setPostTransfoMat(matAltAzModelView);
        return StelProjector::ModelViewTranformP(refr);
}

//! Get the modelview matrix for observer-centric fixed equatorial drawing
StelProjector::ModelViewTranformP StelCore::getFixedEquatorialModelViewTransform(RefractionMode refMode) const
{
        if (refMode==RefractionOff || skyDrawer==Q_NULLPTR || (refMode==RefractionAuto && skyDrawer->getFlagHasAtmosphere()==false))
                return StelProjector::ModelViewTranformP(new StelProjector::Mat4dTransform(matAltAzModelView,matFixedEquatorialToAltAz));
        Refraction* refr = new Refraction(skyDrawer->getRefraction());
        // The pretransform matrix will convert from input coordinates to AltAz needed by the refraction function.
        refr->setPreTransfoMat(matFixedEquatorialToAltAz);
        refr->setPostTransfoMat(matAltAzModelView);
        return StelProjector::ModelViewTranformP(refr);
}

//! Get the modelview matrix for observer-centric altazimuthal drawing
StelProjector::ModelViewTranformP StelCore::getAltAzModelViewTransform(RefractionMode refMode) const
{
        if (refMode==RefractionOff || skyDrawer==Q_NULLPTR || (refMode==RefractionAuto && skyDrawer->getFlagHasAtmosphere()==false))
        {
                // Catch problem with improperly initialized matAltAzModelView
                Q_ASSERT(matAltAzModelView[0]==matAltAzModelView[0]);
                return StelProjector::ModelViewTranformP(new StelProjector::Mat4dTransform(matAltAzModelView,Mat4d::identity()));
        }
        Refraction* refr = new Refraction(skyDrawer->getRefraction());
        // The pretransform matrix will convert from input coordinates to AltAz needed by the refraction function.
        refr->setPostTransfoMat(matAltAzModelView);
        return StelProjector::ModelViewTranformP(refr);
}

//! Get the modelview matrix for observer-centric J2000 equatorial drawing
StelProjector::ModelViewTranformP StelCore::getJ2000ModelViewTransform(RefractionMode refMode) const
{
        if (refMode==RefractionOff || skyDrawer==Q_NULLPTR || (refMode==RefractionAuto && skyDrawer->getFlagHasAtmosphere()==false))
                return StelProjector::ModelViewTranformP(new StelProjector::Mat4dTransform(matAltAzModelView,matEquinoxEquToAltAz*matJ2000ToEquinoxEqu));
        Refraction* refr = new Refraction(skyDrawer->getRefraction());
        // The pretransform matrix will convert from input coordinates to AltAz needed by the refraction function.
        refr->setPreTransfoMat(matEquinoxEquToAltAz*matJ2000ToEquinoxEqu);
        refr->setPostTransfoMat(matAltAzModelView);
        return StelProjector::ModelViewTranformP(refr);
}

//! Get the modelview matrix for observer-centric Galactic equatorial drawing
StelProjector::ModelViewTranformP StelCore::getGalacticModelViewTransform(RefractionMode refMode) const
{
        if (refMode==RefractionOff || skyDrawer==Q_NULLPTR || (refMode==RefractionAuto && skyDrawer->getFlagHasAtmosphere()==false))
                return StelProjector::ModelViewTranformP(new StelProjector::Mat4dTransform(matAltAzModelView,matEquinoxEquToAltAz*matJ2000ToEquinoxEqu*matGalacticToJ2000));
        Refraction* refr = new Refraction(skyDrawer->getRefraction());
        // The pretransform matrix will convert from input coordinates to AltAz needed by the refraction function.
        refr->setPreTransfoMat(matEquinoxEquToAltAz*matJ2000ToEquinoxEqu*matGalacticToJ2000);
        refr->setPostTransfoMat(matAltAzModelView);
        return StelProjector::ModelViewTranformP(refr);
}

//! Get the modelview matrix for observer-centric Supergalactic equatorial drawing
StelProjector::ModelViewTranformP StelCore::getSupergalacticModelViewTransform(RefractionMode refMode) const
{
        if (refMode==RefractionOff || skyDrawer==Q_NULLPTR || (refMode==RefractionAuto && skyDrawer->getFlagHasAtmosphere()==false))
                return StelProjector::ModelViewTranformP(new StelProjector::Mat4dTransform(matAltAzModelView,matEquinoxEquToAltAz*matJ2000ToEquinoxEqu*matSupergalacticToJ2000));
        Refraction* refr = new Refraction(skyDrawer->getRefraction());
        // The pretransform matrix will convert from input coordinates to AltAz needed by the refraction function.
        refr->setPreTransfoMat(matEquinoxEquToAltAz*matJ2000ToEquinoxEqu*matSupergalacticToJ2000);
        refr->setPostTransfoMat(matAltAzModelView);
        return StelProjector::ModelViewTranformP(refr);
}

// GZ: One of the most important functions, totally void of doc. :-(
// called in update() (for every frame)
void StelCore::updateTransformMatrices()
{
        matAltAzToEquinoxEqu = position->getRotAltAzToEquatorial(getJD(), getJDE());
        matEquinoxEquToAltAz = matAltAzToEquinoxEqu.transpose();

        // multiply static J2000 earth axis tilt (eclipticalJ2000<->equatorialJ2000)
        // in effect, this matrix transforms from VSOP87 ecliptical J2000 to planet-based equatorial coordinates.
        // For earth, matJ2000ToEquinoxEqu is the precession matrix.        
        matEquinoxEquDateToJ2000 = matVsop87ToJ2000 * position->getRotEquatorialToVsop87();
        matJ2000ToEquinoxEqu = matEquinoxEquDateToJ2000.transpose();
        matJ2000ToAltAz = matEquinoxEquToAltAz*matJ2000ToEquinoxEqu;
        matAltAzToJ2000 = matJ2000ToAltAz.transpose();

        matHeliocentricEclipticToEquinoxEqu = matJ2000ToEquinoxEqu * matVsop87ToJ2000 * Mat4d::translation(-position->getCenterVsop87Pos());

        // These two next have to take into account the position of the observer on the earth/planet of observation.        
        Mat4d matAltAzToVsop87 = matJ2000ToVsop87 * matEquinoxEquDateToJ2000 * matAltAzToEquinoxEqu;
        //Mat4d tmp1 = matJ2000ToVsop87 * matEquinoxEquDateToJ2000;

        // Before 0.14 getDistanceFromCenter assumed spherical planets. Now uses rectangular coordinates for observer!
        // In series 0.14 and 0.15, this was erroneous: offset by distance rho, but in the wrong direction.
        // Attempt to fix LP:1275092. This improves the situation, but is still not perfect.
        // Please keep the commented stuff until situation is really solved.
        if (flagUseTopocentricCoordinates)
        {
                const Vec4d offset=position->getTopographicOffsetFromCenter(); // [rho cosPhi', rho sinPhi', phi'_rad, rho]
                const double sigma=static_cast<double>(position->getCurrentLocation().getLatitude())*M_PI/180.0 - offset.v[2];
                const double rho=offset.v[3];

                matAltAzToHeliocentricEclipticJ2000 =  Mat4d::translation(position->getCenterVsop87Pos()) * matAltAzToVsop87 *
                                Mat4d::translation(Vec3d(rho*sin(sigma), 0., rho*cos(sigma) ));

                matHeliocentricEclipticJ2000ToAltAz =
                                Mat4d::translation(Vec3d(-rho*sin(sigma), 0., -rho*cos(sigma))) * matAltAzToVsop87.transpose() *
                                Mat4d::translation(-position->getCenterVsop87Pos());

                // Here I tried to split tmp matrix. This does not work:
//                matAltAzToHeliocentricEclipticJ2000 =  Mat4d::translation(position->getCenterVsop87Pos()) * tmp1 *
//                                Mat4d::translation(Vec3d(rho*sin(sigma), 0., rho*cos(sigma) )) * matAltAzToEquinoxEqu;

//                matHeliocentricEclipticJ2000ToAltAz =
//                                matEquinoxEquToAltAz *
//                                Mat4d::translation(Vec3d(-rho*sin(sigma), 0., -rho*cos(sigma))) * tmp1.transpose() *
//                                Mat4d::translation(-position->getCenterVsop87Pos());


//                matAltAzToHeliocentricEclipticJ2000 =  Mat4d::translation(position->getCenterVsop87Pos()) * tmp *
//                                Mat4d::translation(Vec3d(0.,0., position->getDistanceFromCenter()));

//                matHeliocentricEclipticJ2000ToAltAz =  Mat4d::translation(Vec3d(0.,0.,-position->getDistanceFromCenter())) * tmp.transpose() *
//                                Mat4d::translation(-position->getCenterVsop87Pos());
        }
        else
        {
                matAltAzToHeliocentricEclipticJ2000 =  Mat4d::translation(position->getCenterVsop87Pos()) * matAltAzToVsop87;
                matHeliocentricEclipticJ2000ToAltAz =  matAltAzToVsop87.transpose() * Mat4d::translation(-position->getCenterVsop87Pos());
        }
}

// This avoids calling a costly operation every frame.
void StelCore::updateFixedEquatorialTransformMatrices()
{
        matAltAzToFixedEquatorial = Mat4d::yrotation(M_PI_2-static_cast<double>(getCurrentLocation().getLatitude())*M_PI_180);
        matFixedEquatorialToAltAz = matAltAzToFixedEquatorial.transpose();
}
// Return the observer heliocentric position
Vec3d StelCore::getObserverHeliocentricEclipticPos() const
{
        return Vec3d(matAltAzToHeliocentricEclipticJ2000[12], matAltAzToHeliocentricEclipticJ2000[13], matAltAzToHeliocentricEclipticJ2000[14]);
}

// Set the location to use by default at startup
void StelCore::setDefaultLocationID(const QString& id)
{
        StelLocation location = StelApp::getInstance().getLocationMgr().locationForString(id);
        if (!location.isValid())
        {
                qWarning() << "Trying to set an invalid location" << id;
                return;
        }
        defaultLocationID = id;
        QSettings* conf = StelApp::getInstance().getSettings();
        Q_ASSERT(conf);
        conf->setValue("init_location/location", id);
}

void StelCore::returnToDefaultLocation()
{
        StelLocationMgr& locationMgr = StelApp::getInstance().getLocationMgr();
        StelLocation loc = locationMgr.locationForString(defaultLocationID);
        if (loc.isValid())
                moveObserverTo(loc, 0.);
}

void StelCore::returnToHome()
{
        // Using returnToDefaultLocation() and getCurrentLocation() introduce issue, because for flying
        // between planets using SpaceShip and second method give does not exist data
        StelLocationMgr& locationMgr = StelApp::getInstance().getLocationMgr();
        StelLocation loc;
        if (defaultLocationID == "auto")
        {
                locationMgr.locationFromIP();
                loc = locationMgr.getLastResortLocation();
        }
        else
                loc = locationMgr.locationForString(defaultLocationID);

        if (loc.isValid())
                moveObserverTo(loc, 0.);

        PlanetP p = GETSTELMODULE(SolarSystem)->searchByEnglishName(loc.planetName);
        QSettings* conf = StelApp::getInstance().getSettings();

        LandscapeMgr* landscapeMgr = GETSTELMODULE(LandscapeMgr);
        landscapeMgr->setCurrentLandscapeID(landscapeMgr->getDefaultLandscapeID());
        landscapeMgr->setFlagAtmosphere(p->hasAtmosphere() && conf->value("landscape/flag_atmosphere", true).toBool());
        landscapeMgr->setFlagFog(p->hasAtmosphere() && conf->value("landscape/flag_fog", true).toBool());
        landscapeMgr->setFlagLandscape(!p->getEnglishName().contains("observer", Qt::CaseInsensitive) && conf->value("landscape/flag_landscape", true).toBool());

        GETSTELMODULE(StelObjectMgr)->unSelect();

        StelMovementMgr* smmgr = getMovementMgr();
        smmgr->setViewDirectionJ2000(altAzToJ2000(smmgr->getInitViewingDirection(), StelCore::RefractionOff));
        smmgr->zoomTo(smmgr->getInitFov(), 1.);
}

double StelCore::getJDOfLastJDUpdate() const
{
        return jdOfLastJDUpdate;
}

void StelCore::setMilliSecondsOfLastJDUpdate(qint64 millis)
{
        milliSecondsOfLastJDUpdate = millis;
}

qint64 StelCore::getMilliSecondsOfLastJDUpdate() const
{
        return milliSecondsOfLastJDUpdate;
}

void StelCore::setJD(double newJD)
{
        JD.first=newJD;
        JD.second=computeDeltaT(newJD);        
        resetSync();
}

double StelCore::getJD() const
{
        return JD.first;
}

void StelCore::setJDE(double newJDE)
{
        // nitpickerish this is not exact, but as good as it gets...
        JD.second=computeDeltaT(newJDE);
        JD.first=newJDE-JD.second/86400.0;
        resetSync();
}

double StelCore::getJDE() const
{
        return JD.first+JD.second/86400.0;
}


void StelCore::setMJDay(double MJD)
{
        setJD(MJD+2400000.5);
}

double StelCore::getMJDay() const
{
        return JD.first-2400000.5;
}

double StelCore::getPresetSkyTime() const
{
        return presetSkyTime;
}

void StelCore::setPresetSkyTime(double d)
{
        presetSkyTime=d;
}

void StelCore::setTimeRate(double ts)
{
        timeSpeed=ts;
        resetSync();
        emit timeRateChanged(timeSpeed);
}

double StelCore::getTimeRate() const
{
        return timeSpeed;
}

void StelCore::revertTimeDirection(void)
{
        setTimeRate(-1*getTimeRate());
}

void StelCore::moveObserverToSelected()
{
        StelObjectMgr* objmgr = GETSTELMODULE(StelObjectMgr);
        Q_ASSERT(objmgr);
        if (objmgr->getWasSelected())
        {
                Planet* pl = dynamic_cast<Planet*>(objmgr->getSelectedObject()[0].data());
                if (pl)
                {
                        // We need to move to the selected planet. Try to generate a location from the current one
                        StelLocation loc = getCurrentLocation();
                        if (loc.planetName != pl->getEnglishName())
                        {
                                loc.planetName = pl->getEnglishName();                                
                                loc.name = "landing site";
                                loc.state = "";
                                if (pl->getPlanetType()==Planet::isObserver)
                                        loc.role=QChar('o');
                                else
                                        loc.role=QChar('X');

                                // Let's try guess name of location...
                                LocationMap results = StelApp::getInstance().getLocationMgr().pickLocationsNearby(loc.planetName, loc.getLongitude(), loc.getLatitude(), 1.0f);
                                if (results.size()>0)
                                        loc = results.value(results.firstKey()); // ...and use it!

                                moveObserverTo(loc);
                        }
                }
                else
                {
                        NomenclatureItem* ni = dynamic_cast<NomenclatureItem*>(objmgr->getSelectedObject()[0].data());
                        if (ni)
                        {
                                // We need to move to the nomenclature item's host planet.
                                StelLocation loc; //  = getCurrentLocation();
                                loc.planetName = ni->getPlanet()->getEnglishName();
                                loc.name=ni->getEnglishName();
                                loc.state = "";
                                loc.setLongitude(ni->getLongitude());
                                loc.setLatitude(ni->getLatitude());
                                loc.lightPollutionLuminance = 0;

                                moveObserverTo(loc);
                                objmgr->unSelect(); // no use to keep it: Marker will flicker around the screen.
                        }
                }
        }
        StelMovementMgr* mmgr = GETSTELMODULE(StelMovementMgr);
        Q_ASSERT(mmgr);
        mmgr->setFlagTracking(false);
}

// Get the information on the current location
const StelLocation& StelCore::getCurrentLocation() const
{
        return position->getCurrentLocation();
}

const QSharedPointer<Planet> StelCore::getCurrentPlanet() const
{
        return position->getHomePlanet();
}

const StelObserver *StelCore::getCurrentObserver() const
{
        return position;
}

void StelCore::setObserver(StelObserver *obs)
{
        delete position;
        position = obs;
        if (!getUseCustomTimeZone() && obs->getCurrentLocation().ianaTimeZone.length()>0)
                setCurrentTimeZone(obs->getCurrentLocation().ianaTimeZone);
}

// Smoothly move the observer to the given location
void StelCore::moveObserverTo(const StelLocation& target, double duration, double durationIfPlanetChange, const QString &landscapeID)
{
        double d = (getCurrentLocation().planetName==target.planetName) ? duration : durationIfPlanetChange;
        if (d>0.)
        {
                StelLocation curLoc = getCurrentLocation();
                if (position->isTraveling())
                {
                        // Avoid using a temporary location name to create another temporary one (otherwise it looks like loc1 -> loc2 -> loc3 etc..)
                        curLoc.name = ".";
                }
                SpaceShipObserver* newObs = new SpaceShipObserver(curLoc, target, d);                
                setObserver(newObs);
                newObs->update(0);
        }
        else
        {
                setObserver(new StelObserver(target));
        }

        // Auto-select observed planet for observer locations
        if (target.role==QChar('o'))
        {
                // If we change to an Observer "planet", auto-select and focus on the observed object.
                SolarSystem *ss=GETSTELMODULE(SolarSystem);
                PlanetP planet=nullptr;
                if (ss)
                        planet=GETSTELMODULE(SolarSystem)->searchByEnglishName(target.planetName);
                if (planet && planet->getPlanetType()==Planet::isObserver)
                {
                        StelObjectMgr *soMgr=GETSTELMODULE(StelObjectMgr);
                        if (soMgr)
                        {
                                soMgr->findAndSelect(planet->getParent()->getEnglishName());
                                GETSTELMODULE(StelMovementMgr)->setFlagTracking(true);
                        }
                }
        }
        emit targetLocationChanged(target, landscapeID);
        emit locationChanged(getCurrentLocation());
}

double StelCore::getUTCOffset(const double JD) const
{
        int year, month, day, hour, minute, second;
        StelUtils::getDateTimeFromJulianDay(JD, &year, &month, &day, &hour, &minute, &second);
        // as analogous to second statement in getJDFromDate, nkerr
        if ( year <= 0 )
        {
                year = year - 1;
        }
        //getTime/DateFromJulianDay returns UTC time, not local time
        QDateTime universal(QDate(year, month, day), QTime(hour, minute, second), Qt::UTC);
        if (!universal.isValid())
        {
                //qWarning() << "JD " << QString("%1").arg(JD) << " out of bounds of QT help with GMT shift, using current datetime";
                // Assumes the GMT shift was always the same before year -4710
                // NOTE: QDateTime has no year 0, and therefore likely different leap year rules.
                // Under which circumstances do we get invalid universal?
                universal = QDateTime(QDate(-4710, month, day), QTime(hour, minute, second), Qt::UTC);
        }

#if defined(Q_OS_WIN)
        if (abs(year)<3)
        {
                // Mitigate a QTBUG on Windows (GH #594).
                // This bug causes offset to be MIN_INT in January to March, 1AD.
                // We assume a constant offset in this remote history,
                // so we construct yet another date to get a valid offset.
                // Application of the named time zones is inappropriate in any case.
                universal = QDateTime(QDate(3, month, day), QTime(hour, minute, second), Qt::UTC);
        }
#endif
        StelLocation loc = getCurrentLocation();
        QString tzName = getCurrentTimeZone();
        QTimeZone tz(tzName.toUtf8());
        // We must fight a bug in Qt6.2 on Linux. For some reason tz.isValid() is true even for our self-named zones LMST,LTST,system_default.
        // We must use an intermediate Boolean which we set to false where needed.
        bool tzValid=tz.isValid();
        if (QString("LMST LTST system_default").contains(tzName))
                tzValid=false;
        if (!tzValid && !QString("LMST LTST system_default").contains(tzName))
        {
                qWarning() << "Invalid timezone: " << tzName;
        }

        qint64 shiftInSeconds = 0;
        if (tzName=="system_default" || (loc.planetName=="Earth" && !tzValid && !QString("LMST LTST").contains(tzName)))
        {
                QDateTime local = universal.toLocalTime();
                //Both timezones should be interpreted as UTC because secsTo() converts both
                //times to UTC if their zones have different daylight saving time rules.
                local.setTimeSpec(Qt::UTC);
                shiftInSeconds = universal.secsTo(local);
                if (abs(shiftInSeconds)>50000 || shiftInSeconds==INT_MIN)
                {
                        qDebug() << "TZ system_default or invalid, At JD" << QString::number(JD, 'g', 11) << ", shift:" << shiftInSeconds;
                }
        }
        else
        {
                // The first adoption of a standard time was on December 1, 1847 in Great Britain
                if (tzValid && loc.planetName=="Earth" && (JD>=StelCore::TZ_ERA_BEGINNING || getUseCustomTimeZone()))
                {
                        if (getUseDST())
                                shiftInSeconds = tz.offsetFromUtc(universal);
                        else
                                shiftInSeconds = tz.standardTimeOffset(universal);
                        if (abs(shiftInSeconds)>500000 || shiftInSeconds==INT_MIN)
                        {
                                // Something very strange has happened. The Windows-only clause above already mitigated GH #594.
                                // Trigger this with a named custom TZ like Europe/Stockholm.
                                // Then try to wheel back some date in January-March from year 10 to 0. Instead of year 1, it jumps to 70,
                                // an offset of INT_MIN
                                qWarning() << "ERROR TRAPPED! --- Please submit a bug report with this logfile attached.";
                                qWarning() << "TZ" << tz << "valid, but at JD" << QString::number(JD, 'g', 11) << ", shift:" << shiftInSeconds;
                                qWarning() << "Universal reference date: " << universal.toString();
                        }
                }
                else
                {
                        shiftInSeconds = qRound((loc.getLongitude()/15.f)*3600.f); // Local Mean Solar Time
                }
                if (tzName=="LTST")
                        shiftInSeconds += qRound(getSolutionEquationOfTime()*60);
        }
        //qDebug() << "ShiftInSeconds:" << shiftInSeconds;
        #ifdef Q_OS_WIN
        // A dirty hack for report: https://github.com/Stellarium/stellarium/issues/686
        // TODO: switch to IANA TZ on all operating systems
        if (tzName=="Europe/Volgograd")
                shiftInSeconds = 4*3600; // UTC+04:00
        #endif

        // Extraterrestrial: Either use the configured Terrestrial timezone, or even a pseudo-LMST based on planet's rotation speed?
        if (loc.planetName!="Earth")
        {
                if (tzValid && (JD>=StelCore::TZ_ERA_BEGINNING || getUseCustomTimeZone()))
                {
                        if (getUseDST())
                                shiftInSeconds = tz.offsetFromUtc(universal);
                        else
                                shiftInSeconds = tz.standardTimeOffset(universal);
                        if (shiftInSeconds==INT_MIN) // triggered error
                        {
                                // Something very strange has happened. The Windows-only clause above already mitigated GH #594.
                                // Trigger this with a named custom TZ like Europe/Stockholm.
                                // Then try to wheel back some date in January-March from year 10 to 0. Instead of year 1, it jumps to 70,
                                // an offset of INT_MIN
                                qWarning() << "ERROR TRAPPED! --- Please submit a bug report with this logfile attached.";
                                qWarning() << "TZ" << tz << "valid, but at JD" << QString::number(JD, 'g', 11) << ", shift:" << shiftInSeconds;
                                qWarning() << "Universal reference date: " << universal.toString();
                        }
                }
                else
                {
                        // TODO: This should give "mean solar time" for any planet.
                        // Combine rotation and orbit, or (for moons) rotation and orbit of parent planet.
                        // LTST is even worse, needs equation of time for other planets.
                        shiftInSeconds = 0; // For now, give UT
                }
        }

        return shiftInSeconds / 3600.0;
}

QString StelCore::getCurrentTimeZone() const
{
        return currentTimeZone;
}

void StelCore::setCurrentTimeZone(const QString& tz)
{
        if (StelApp::getInstance().getLocationMgr().getAllTimezoneNames().contains(tz))
        {
                currentTimeZone = tz;
                emit currentTimeZoneChanged(tz);
        }
        else
        {
                qWarning() << "StelCore: Invalid timezone name:" << tz << " -- not setting timezone.";
        }
}

bool StelCore::getUseDST() const
{
        return flagUseDST;
}

void StelCore::setUseDST(const bool b)
{
        flagUseDST = b;
        StelApp::getInstance().getSettings()->setValue("localization/flag_dst", b);
        emit flagUseDSTChanged(b);
}

void StelCore::setDitheringMode(const DitheringMode newMode)
{
        if(newMode == ditheringMode)
                return;

        ditheringMode = newMode;
        emit ditheringModeChanged(newMode);
}

void StelCore::setDitheringMode(const QString& modeName)
{
        const auto mode = parseDitheringMode(modeName);
        setDitheringMode(mode);
}

bool StelCore::getUseCustomTimeZone() const
{
        return flagUseCTZ;
}

void StelCore::setUseCustomTimeZone(const bool b)
{
        flagUseCTZ = b;
        emit useCustomTimeZoneChanged(b);
}

double StelCore::getSolutionEquationOfTime(const double JDE) const
{
        // The full solution to the equation of time requires lots of computation. We go the fast way from Meeus, AA2, 28.3.

        const double T=(JDE-2451545.0)/36525.;
        const double tau = T*0.1;
        const double epsRad=getPrecessionAngleVondrakEpsilon(JDE);
        const double e = (-0.0000001267*T-0.000042037)*T+0.016708634;
        const double M = ((-0.0001537*T+35999.05029)*T+357.52911)*M_PI_180;
        double Lo = StelUtils::fmodpos(280.4664567 + tau*(360007.6982779 + tau*(0.03032028 + tau*(1./49931. + tau*(-1./15300. - tau/2000000.)))), 360.);
        Lo *= M_PI_180;
        double y=tan(epsRad*0.5); y*=y;

        double E=y*sin(2.*Lo)+2.*e*sin(M)*(2.*y*cos(2.*Lo)-1.)-0.5*y*y*sin(4.*Lo)-1.25*e*e*sin(2.*M);
        return E*M_180_PI*4.;
}

double StelCore::getSolutionEquationOfTime() const
{
        const double tau = (getJDE() - 2451545.0)/365250.0;
        const double sunMeanLongitude = StelUtils::fmodpos(280.4664567 + tau*(360007.6982779 + tau*(0.03032028 + tau*(1./49931. + tau*(-1./15300. - tau/2000000.)))), 360.);

        Vec3d pos = GETSTELMODULE(StelObjectMgr)->searchByName("Sun")->getEquinoxEquatorialPos(this);
        double ra, dec;
        StelUtils::rectToSphe(&ra, &dec, pos);

        // convert radians to degrees and reduce the angle, so that 0 <= angle < 360
        const double alpha = StelUtils::fmodpos(ra*M_180_PI, 360.);

        double deltaPsi, deltaEps;
        getNutationAngles(getJDE(), &deltaPsi, &deltaEps); // these are radians!
        double equation = 4*(sunMeanLongitude - 0.0057183 - alpha + deltaPsi*M_180_PI*cos(getPrecessionAngleVondrakEpsilon(getJDE())));
        // The equation of time is always smaller 20 minutes in absolute value
        if (qAbs(equation)>20)
        {
                // If absolute value of the equation of time appears to be too large, add 24 hours (1440 minutes) to or subtract it from our result
                if (equation>0.)
                        equation -= 1440.;
                else
                        equation += 1440.;
        }

        return equation;
}

//! Set stellarium time to current real world time
void StelCore::setTimeNow()
{
        setJD(StelUtils::getJDFromSystem());
        // Force emit dateChanged
        emit dateChanged();
}

void StelCore::setTodayTime(const QTime& target)
{
        QDateTime dt = QDateTime::currentDateTime();
        if (target.isValid())
        {
                dt.setTime(target);
                // don't forget to adjust for timezone / daylight savings.
                double JD = StelUtils::qDateTimeToJd(dt)-(static_cast<double>(getUTCOffset(StelUtils::getJDFromSystem())) * JD_HOUR);
                setJD(JD);
        }
        else
        {
                qWarning() << "WARNING - time passed to StelCore::setTodayTime is not valid. The system time will be used." << target;
                setTimeNow();
        }
}

//! Get whether the current stellarium time is the real world time
bool StelCore::getIsTimeNow(void) const
{
        // cache last time to prevent to much slow system call
        static double lastJD = getJD();
        static bool previousResult = (fabs(getJD()-(StelUtils::getJDFromSystem()))<JD_SECOND);
        if (fabs(lastJD-getJD())>JD_SECOND/4)
        {
                lastJD = getJD();
                previousResult = (fabs(getJD()-(StelUtils::getJDFromSystem()))<JD_SECOND);
        }
        return previousResult;
}

QTime StelCore::getInitTodayTime(void) const
{
        return initTodayTime;
}

void StelCore::setInitTodayTime(const QTime& time)
{
        initTodayTime=time;
}

void StelCore::setPresetSkyTime(QDateTime dateTime)
{
        setPresetSkyTime(StelUtils::qDateTimeToJd(dateTime));
}

void StelCore::addMinute()
{
        addSolarDays(JD_MINUTE);
}

void StelCore::addHour()
{
        addSolarDays(JD_HOUR);
}

void StelCore::addDay()
{
        addSolarDays(1.0);
}

void StelCore::addWeek()
{
        addSolarDays(7.0);
}

void StelCore::addSiderealDay()
{
        addSiderealDays(1.0);
}

void StelCore::addSiderealWeek()
{
        addSiderealDays(7.0);
}

void StelCore::addSiderealYear()
{
        addSiderealYears(1.);
}

void StelCore::addSiderealYears(double n)
{
        double days = 365.256363004;
        double sidereal = getLocalSiderealYearLength();
        Planet::PlanetType ptype = getCurrentPlanet()->getPlanetType();
        if (ptype!=Planet::isObserver && ptype!=Planet::isArtificial && sidereal>0.)
                days = sidereal;

        addSolarDays(days*n);
}

void StelCore::addSynodicMonth()
{
        addSolarDays(29.530588853);
}

void StelCore::addSaros()
{
        // 223 synodic months
        addSolarDays(223*29.530588853);
}

void StelCore::addDraconicMonth()
{
        addSolarDays(27.212220817);
}

void StelCore::addMeanTropicalMonth()
{
        addSolarDays(27.321582241);
}

void StelCore::addCalendricMonth()
{
        double cjd = getJD();
        int year, month, day, hour, minute, second;
        StelUtils::getDateTimeFromJulianDay(cjd, &year, &month, &day, &hour, &minute, &second);
        month++;
        if (month>12)
        {
                month = 1;
                year++;
        }
        StelUtils::getJDFromDate(&cjd, year, month, day, hour, minute, static_cast<float>(second));
        setJD(cjd);
}

void StelCore::addAnomalisticMonth()
{
        addSolarDays(27.554549878);
}

void StelCore::addAnomalisticYear()
{
        addAnomalisticYears(1.);
}

void StelCore::addAnomalisticYears(double n)
{
        addSolarDays(365.259636*n);
}

void StelCore::addDraconicYear()
{
        addSolarDays(346.620075883);
}

void StelCore::addMeanTropicalYear()
{
        addMeanTropicalYears(1.0);
}

void StelCore::addTropicalYear()
{
        // Source: J. Meeus. More Mathematical Astronomy Morsels. 2002, p. 358.
        // Meeus, J. & Savoie, D. The history of the tropical year. Journal of the British Astronomical Association, vol.102, no.1, p.40-42
        // http://articles.adsabs.harvard.edu//full/1992JBAA..102...40M
        const double T = (getJD()-2451545.0)/365250.0;
        addSolarDays(365.242189623 - T*(0.000061522 - T*(0.0000000609 + T*0.00000026525)));
}

void StelCore::addMeanTropicalYears(double n)
{        
        // Source: https://en.wikipedia.org/wiki/Tropical_year#Mean_tropical_year_current_value
        addSolarDays(365.2421897*n); // The mean tropical year on January 1, 2000
}

void StelCore::addJulianYear()
{
        addJulianYears(1.);
}

void StelCore::addGaussianYear()
{
        addSolarDays(365.2568983);
}

void StelCore::addJulianYears(double n)
{
        addSolarDays(365.25*n);
}

void StelCore::subtractMinute()
{
        addSolarDays(-JD_MINUTE);
}

void StelCore::subtractHour()
{
        addSolarDays(-JD_HOUR);
}

void StelCore::subtractDay()
{
        addSolarDays(-1.0);
}

void StelCore::subtractWeek()
{
        addSolarDays(-7.0);
}

void StelCore::subtractSiderealDay()
{
        addSiderealDays(-1.0);
}

void StelCore::subtractSiderealWeek()
{
        addSiderealDays(-7.0);
}

void StelCore::subtractSiderealYear()
{
        addSiderealYears(-1.);
}

void StelCore::subtractSiderealYears(double n)
{
        addSiderealYears(-n);
}

void StelCore::subtractSynodicMonth()
{
        addSolarDays(-29.530588853);
}

void StelCore::subtractSaros()
{
        // 223 synodic months
        addSolarDays(-223*29.530588853);
}

void StelCore::subtractDraconicMonth()
{
        addSolarDays(-27.212220817);
}

void StelCore::subtractMeanTropicalMonth()
{
        addSolarDays(-27.321582241);
}

void StelCore::subtractCalendricMonth()
{
        double cjd = getJD();
        int year, month, day, hour, minute, second;
        StelUtils::getDateTimeFromJulianDay(cjd, &year, &month, &day, &hour, &minute, &second);
        month--;
        if (month<1)
        {
                month = 12;
                year--;
        }
        StelUtils::getJDFromDate(&cjd, year, month, day, hour, minute, static_cast<float>(second));
        setJD(cjd);
}

void StelCore::subtractAnomalisticMonth()
{
        addSolarDays(-27.554549878);
}

void StelCore::subtractAnomalisticYear()
{
        subtractAnomalisticYears(1.);
}

void StelCore::subtractAnomalisticYears(double n)
{
        addSolarDays(-365.259636*n);
}

void StelCore::subtractDraconicYear()
{
        addSolarDays(-346.620075883);
}

void StelCore::subtractTropicalYear()
{
        // Source: J. Meeus. More Mathematical Astronomy Morsels. 2002, p. 358.
        double T = (getJD()-2451545.0)/365250.0;
        addSolarDays(-(365.242189623 - T*(0.000061522 - T*(0.0000000609 + T*0.00000026525))));
}

void StelCore::subtractMeanTropicalYear()
{
        addMeanTropicalYears(-1.0);
}

void StelCore::subtractMeanTropicalYears(double n)
{
        addMeanTropicalYears(-1.0*n);
}

void StelCore::subtractJulianYear()
{
        addSolarDays(-365.25);
}

void StelCore::subtractGaussianYear()
{
        addSolarDays(-365.2568983);
}

void StelCore::subtractJulianYears(double n)
{
        addSolarDays(-365.25*n);
}

void StelCore::addSolarDays(double d)
{
        const PlanetP& home = getCurrentPlanet();
        Planet::PlanetType ptype = home->getPlanetType();
        if (ptype!=Planet::isArtificial && ptype!=Planet::isObserver)
                d *= home->getMeanSolarDay();

        setJD(getJD() + d);

        if (qAbs(d)>0.99) // WTF: qAbs(d)>=1.0 not working here!
                emit dateChanged();
}

void StelCore::addSiderealDays(double d)
{
        const PlanetP& home = getCurrentPlanet();
        Planet::PlanetType ptype = home->getPlanetType();
        if (ptype!=Planet::isArtificial && ptype!=Planet::isObserver)
                d *= home->getSiderealDay();

        setJD(getJD() + d);
}

// Get the sidereal time of the prime meridian (i.e. Rotation Angle) shifted by the observer longitude
double StelCore::getLocalSiderealTime() const
{
        // On Earth, this requires UT deliberately with all its faults, on other planets we use the more regular TT.
        return (getCurrentPlanet()->getSiderealTime(getJD(), getJDE())+static_cast<double>(position->getCurrentLocation().getLongitude()))*M_PI/180.;
}

//! Get the duration of a sidereal day for the current observer in day.
double StelCore::getLocalSiderealDayLength() const
{
        return getCurrentPlanet()->getSiderealDay();
}

//! Get the duration of a sidereal year for the current observer in days.
double StelCore::getLocalSiderealYearLength() const
{
        return getCurrentPlanet()->getSiderealPeriod();
}

QString StelCore::getStartupTimeMode() const
{
        return startupTimeMode;
}

//! Increase the time speed
void StelCore::increaseTimeSpeed()
{
        double s = getTimeRate();
        if (s>=JD_SECOND) s*=10.;
        else if (s<-JD_SECOND) s/=10.;
        else if (s>=0.) s=JD_SECOND;
        else s=0.;
        setTimeRate(s);
}

//! Decrease the time speed
void StelCore::decreaseTimeSpeed()
{
        double s = getTimeRate();
        if (s>JD_SECOND) s/=10.;
        else if (s<=-JD_SECOND) s*=10.;
        else if (s<=0.) s=-JD_SECOND;
        else s=0.;
        setTimeRate(s);
}

void StelCore::increaseTimeSpeedLess()
{
        double s = getTimeRate();
        if (s>=JD_SECOND) s*=2.;
        else if (s<-JD_SECOND) s/=2.;
        else if (s>=0.) s=JD_SECOND;
        else s=0.;
        setTimeRate(s);
}

void StelCore::decreaseTimeSpeedLess()
{
        double s = getTimeRate();
        if (s>JD_SECOND) s/=2.;
        else if (s<=-JD_SECOND) s*=2.;
        else if (s<=0.) s=-JD_SECOND;
        else s=0.;
        setTimeRate(s);
}

void StelCore::setZeroTimeSpeed()
{
        setTimeRate(0);
}

void StelCore::setRealTimeSpeed()
{
        setTimeRate(JD_SECOND);
}

void StelCore::toggleRealTimeSpeed()
{
        (!getRealTimeSpeed()) ? setRealTimeSpeed() : setZeroTimeSpeed();
}

bool StelCore::getRealTimeSpeed() const
{
        return (fabs(timeSpeed-JD_SECOND)<0.0000001);
}

////////////////////////////////////////////////////////////////////////////////
// Increment time
void StelCore::updateTime(double deltaTime)
{
        if (getRealTimeSpeed())
        {
                JD.first = jdOfLastJDUpdate + (QDateTime::currentMSecsSinceEpoch() - milliSecondsOfLastJDUpdate) / 1000.0 * JD_SECOND;
        }
        else
        {
                JD.first = jdOfLastJDUpdate + (QDateTime::currentMSecsSinceEpoch() - milliSecondsOfLastJDUpdate) / 1000.0 * timeSpeed;
        }

        // Fix time limits to -100000 to +100000 to prevent bugs
        if (JD.first>38245309.499988) JD.first = 38245309.499988;
        if (JD.first<-34803211.500012) JD.first = -34803211.500012;
        JD.second=computeDeltaT(JD.first);

        if (position->isObserverLifeOver())
        {
                // Unselect if the new home planet is the previously selected object
                StelObjectMgr* objmgr = GETSTELMODULE(StelObjectMgr);
                Q_ASSERT(objmgr);
                if (objmgr->getWasSelected() && objmgr->getSelectedObject()[0].data()==getCurrentPlanet())
                {
                        objmgr->unSelect();
                }
                StelObserver* newObs = position->getNextObserver();
                delete position;
                position = newObs;
        }
        if (position->update(deltaTime))
                emit locationChanged(getCurrentLocation());

        // Position of sun and all the satellites (ie planets)
        // GZ maybe setting this static can speedup a bit?
        static SolarSystem* solsystem = static_cast<SolarSystem*>(StelApp::getInstance().getModuleMgr().getModule("SolarSystem"));
        // Likely the most important location where we need JDE:
        solsystem->computePositions(getJDE(), getCurrentPlanet());
}

void StelCore::resetSync()
{
        jdOfLastJDUpdate = getJD();
        //use currentMsecsSinceEpoch directly instead of StelApp::getTotalRuntime,
        //because the StelApp::startMSecs gets subtracted anyways in update()
        //also changed to qint64 to increase precision
        milliSecondsOfLastJDUpdate = QDateTime::currentMSecsSinceEpoch();
        emit timeSyncOccurred(jdOfLastJDUpdate);
}

void StelCore::registerMathMetaTypes()
{
        //enables use of these types in QVariant, StelProperty, signals and slots
        qRegisterMetaType<Vec2d>();
        qRegisterMetaType<Vec2f>();
        qRegisterMetaType<Vec2i>();
        qRegisterMetaType<Vec3d>();
        qRegisterMetaType<Vec3f>();
        qRegisterMetaType<Vec3i>();
        qRegisterMetaType<Vec4d>();
        qRegisterMetaType<Vec4f>();
        qRegisterMetaType<Vec4i>();
        qRegisterMetaType<Mat4d>();
        qRegisterMetaType<Mat4f>();
        qRegisterMetaType<Mat3d>();
        qRegisterMetaType<Mat3f>();

#if (QT_VERSION<QT_VERSION_CHECK(6,0,0))
        //registers the QDataStream operators, so that QVariants with these types can be saved
        qRegisterMetaTypeStreamOperators<Vec2d>();
        qRegisterMetaTypeStreamOperators<Vec2f>();
        qRegisterMetaTypeStreamOperators<Vec2i>();
        qRegisterMetaTypeStreamOperators<Vec3d>();
        qRegisterMetaTypeStreamOperators<Vec3f>();
        qRegisterMetaTypeStreamOperators<Vec3i>();
        qRegisterMetaTypeStreamOperators<Vec4d>();
        qRegisterMetaTypeStreamOperators<Vec4f>();
        qRegisterMetaTypeStreamOperators<Vec4i>();
        qRegisterMetaTypeStreamOperators<Mat4d>();
        qRegisterMetaTypeStreamOperators<Mat4f>();
        qRegisterMetaTypeStreamOperators<Mat3d>();
        qRegisterMetaTypeStreamOperators<Mat3f>();
#endif
        //for debugging QVariants with these types, it helps if we register the string converters
        // This is also required for QJSEngine.
        QMetaType::registerConverter(&Vec2d::toString);
        QMetaType::registerConverter(&Vec2f::toString);
        QMetaType::registerConverter(&Vec2i::toString);
        QMetaType::registerConverter(&Vec3d::toString);
        QMetaType::registerConverter(&Vec3f::toString);
        QMetaType::registerConverter(&Vec3i::toString);
        QMetaType::registerConverter(&Vec4d::toString);
        QMetaType::registerConverter(&Vec4f::toString);
        QMetaType::registerConverter(&Vec4i::toString);

        //Hopefully this works to convert types in scripts when given as String "[...]"
        // Maybe even make brackets optional!
        // Nope, does not work for QJSEngine.
//        QMetaType::registerConverter<QString, Vec2d>(&Vec2d::fromBracketedString);
//        QMetaType::registerConverter<QString, Vec2f>(&Vec2f::fromBracketedString);
//        QMetaType::registerConverter<QString, Vec2i>(&Vec2i::fromBracketedString);
//        QMetaType::registerConverter<QString, Vec3d>(&Vec3d::fromBracketedString);
//        QMetaType::registerConverter<QString, Vec3f>(&Vec3f::fromBracketedString);
//        QMetaType::registerConverter<QString, Vec3i>(&Vec3i::fromBracketedString);
//        QMetaType::registerConverter<QString, Vec4d>(&Vec4d::fromBracketedString);
//        QMetaType::registerConverter<QString, Vec4f>(&Vec4f::fromBracketedString);
//        QMetaType::registerConverter<QString, Vec4i>(&Vec4i::fromBracketedString);
}

void StelCore::setStartupTimeMode(const QString& s)
{
        startupTimeMode = s;
}

// return precomputed DeltaT in seconds. Public.
double StelCore::getDeltaT() const
{
        return JD.second;
}


// compute and return DeltaT in seconds. Try not to call it directly, current DeltaT, JD, and JDE are available.
double StelCore::computeDeltaT(const double JD)
{
        double DeltaT = 0.;
        if (currentDeltaTAlgorithm==Custom)
        {
                // User defined coefficients for quadratic equation for DeltaT may change frequently.
                deltaTnDot = deltaTCustomNDot; // n.dot = custom value "/cy/cy
                int year, month, day;
                StelUtils::getDateFromJulianDay(JD, &year, &month, &day);
                double u = (StelUtils::yearFraction(year,month,day)-getDeltaTCustomYear())/100.;
                DeltaT = deltaTCustomEquationCoeff[0] + u*(deltaTCustomEquationCoeff[1] + u*deltaTCustomEquationCoeff[2]);
        }

        else
        {
                Q_ASSERT(deltaTfunc);
                DeltaT=deltaTfunc(JD);
        }

        if (!deltaTdontUseMoon)
                DeltaT += StelUtils::getMoonSecularAcceleration(JD, deltaTnDot, ((de440Active&&EphemWrapper::jd_fits_de440(JD)) ||
                                                                                 (de441Active&&EphemWrapper::jd_fits_de441(JD)) ||
                                                                                 (de430Active&&EphemWrapper::jd_fits_de430(JD)) ||
                                                                                 (de431Active&&EphemWrapper::jd_fits_de431(JD))));

        return DeltaT;
}

// set a function pointer here. This should make the actual computation simpler by just calling the function.
void StelCore::setCurrentDeltaTAlgorithm(DeltaTAlgorithm algorithm)
{
        currentDeltaTAlgorithm=algorithm;
        deltaTdontUseMoon = false; // most algorithms will use it!
        switch (currentDeltaTAlgorithm)
        {
                case WithoutCorrection:
                        // Without correction, DeltaT is disabled
                        deltaTfunc = StelUtils::getDeltaTwithoutCorrection;
                        deltaTnDot = -26.; // n.dot = -26.0"/cy/cy OR WHAT SHALL WE DO HERE?
                        deltaTdontUseMoon = true;
                        deltaTstart        = INT_MIN;
                        deltaTfinish        = INT_MAX;
                        break;
                case Schoch:
                        // Schoch (1931) algorithm for DeltaT
                        deltaTnDot = -29.68; // n.dot = -29.68"/cy/cy
                        deltaTfunc = StelUtils::getDeltaTBySchoch;
                        deltaTstart        = -300;
                        deltaTfinish        = 1980;
                        break;
                case Clemence:
                        // Clemence (1948) algorithm for DeltaT
                        deltaTnDot = -22.44; // n.dot = -22.44 "/cy/cy
                        deltaTfunc = StelUtils::getDeltaTByClemence;
                        deltaTstart        = 1681;
                        deltaTfinish        = 1900;
                        break;
                case IAU:
                        // IAU (1952) algorithm for DeltaT, based on observations by Spencer Jones (1939)
                        deltaTnDot = -22.44; // n.dot = -22.44 "/cy/cy
                        deltaTfunc = StelUtils::getDeltaTByIAU;
                        deltaTstart        = 1681;
                        deltaTfinish        = 1936; // Details in http://adsabs.harvard.edu/abs/1939MNRAS..99..541S
                        break;
                case AstronomicalEphemeris:
                        // Astronomical Ephemeris (1960) algorithm for DeltaT
                        deltaTnDot = -22.44; // n.dot = -22.44 "/cy/cy
                        deltaTfunc = StelUtils::getDeltaTByAstronomicalEphemeris;
                        // GZ: What is the source of "1681..1900"? Expl.Suppl.AE 1961-p87 says "...over periods extending back to ancient times"
                        // I changed to what I estimate.
                        deltaTstart        = -500; // 1681;
                        deltaTfinish        =  2000; // 1900;
                        break;
                case TuckermanGoldstine:
                        // Tuckerman (1962, 1964) & Goldstine (1973) algorithm for DeltaT
                        //FIXME: n.dot
                        deltaTnDot = -22.44; // n.dot = -22.44 "/cy/cy ???
                        deltaTfunc = StelUtils::getDeltaTByTuckermanGoldstine;
                        deltaTstart        = -600;
                        deltaTfinish        = 1649;
                        break;
                case MullerStephenson:
                        // Muller & Stephenson (1975) algorithm for DeltaT
                        deltaTnDot = -37.5; // n.dot = -37.5 "/cy/cy
                        deltaTfunc = StelUtils::getDeltaTByMullerStephenson;
                        deltaTstart        = -1375;
                        deltaTfinish        = 1975;
                        break;
                case Stephenson1978:
                        // Stephenson (1978) algorithm for DeltaT
                        deltaTnDot = -30.0; // n.dot = -30.0 "/cy/cy
                        deltaTfunc = StelUtils::getDeltaTByStephenson1978;
                        deltaTstart        = INT_MIN; // Range unknown!
                        deltaTfinish        = INT_MAX;
                        break;
                case SchmadelZech1979:
                        // Schmadel & Zech (1979) algorithm for DeltaT
                        deltaTnDot = -23.8946; // n.dot = -23.8946 "/cy/cy
                        deltaTfunc = StelUtils::getDeltaTBySchmadelZech1979;
                        deltaTstart        = 1800;
                        deltaTfinish        = 1975;
                        break;
                case MorrisonStephenson1982:
                        // Morrison & Stephenson (1982) algorithm for DeltaT (used by RedShift)
                        deltaTnDot = -26.0; // n.dot = -26.0 "/cy/cy
                        deltaTfunc = StelUtils::getDeltaTByMorrisonStephenson1982;
                        // FIXME: Is it valid range?
                        deltaTstart        = -4000;
                        deltaTfinish        = 2800;
                        break;
                case StephensonMorrison1984:
                        // Stephenson & Morrison (1984) algorithm for DeltaT
                        deltaTnDot = -26.0; // n.dot = -26.0 "/cy/cy
                        deltaTfunc = StelUtils::getDeltaTByStephensonMorrison1984;
                        deltaTstart        = -391;
                        deltaTfinish        = 1600; // TODO: 1630..1980 are tabulated values
                        break;
                case StephensonHoulden:
                        // Stephenson & Houlden (1986) algorithm for DeltaT.
                        deltaTnDot = -26.0; // n.dot = -26.0 "/cy/cy
                        deltaTfunc = StelUtils::getDeltaTByStephensonHoulden;
                        deltaTstart        = -1500;
                        deltaTfinish        = 1600; // TODO: 1630..1980 are tabulated values from Stephenson & Morrison (1984)
                        break;
                case Espenak:
                        // Espenak (1987, 1989) algorithm for DeltaT
                        //FIXME: n.dot
                        deltaTnDot = -23.8946; // n.dot = -23.8946 "/cy/cy ???
                        deltaTfunc = StelUtils::getDeltaTByEspenak;
                        deltaTstart        = 1950;
                        deltaTfinish        = 2100;
                        break;
                case Borkowski:
                        // Borkowski (1988) algorithm for DeltaT, relates to ELP2000-85!
                        deltaTnDot = -23.895; // GZ: I see -23.895 in the paper, not -23.859; (?) // n.dot = -23.859 "/cy/cy
                        deltaTfunc = StelUtils::getDeltaTByBorkowski;
                        deltaTstart        = -2136;
                        deltaTfinish        = 1715;
                        break;
                case SchmadelZech1988:
                        // Schmadel & Zech (1988) algorithm for DeltaT
                        //FIXME: n.dot
                        deltaTnDot = -26.0; // n.dot = -26.0 "/cy/cy ???
                        deltaTfunc = StelUtils::getDeltaTBySchmadelZech1988;
                        deltaTstart        = 1800;
                        deltaTfinish        = 1988;
                        break;
                case ChaprontTouze:
                        // Chapront-Touzé & Chapront (1991) algorithm for DeltaT
                        deltaTnDot = -23.8946; // n.dot = -23.8946 "/cy/cy
                        deltaTfunc = StelUtils::getDeltaTByChaprontTouze;
                        // FIXME: Is it valid range?
                        deltaTstart        = -4000;
                        deltaTfinish        = 8000;
                        break;
                case StephensonMorrison1995:
                        // Stephenson & Morrison (1995) algorithm for DeltaT
                        deltaTnDot = -26.0; // n.dot = -26.0 "/cy/cy
                        deltaTfunc = StelUtils::getDeltaTByStephensonMorrison1995;
                        deltaTstart        = -700;
                        deltaTfinish        = 1600;
                        break;
                case Stephenson1997:
                        // Stephenson (1997) algorithm for DeltaT
                        deltaTnDot = -26.0; // n.dot = -26.0 "/cy/cy
                        deltaTfunc = StelUtils::getDeltaTByStephenson1997;
                        deltaTstart        = -500;
                        deltaTfinish        = 1600;
                        break;
                case ChaprontMeeus:
                        // Chapront, Chapront-Touze & Francou (1997) & Meeus (1998) algorithm for DeltaT
                        deltaTnDot = -25.7376; // n.dot = -25.7376 "/cy/cy
                        deltaTfunc = StelUtils::getDeltaTByChaprontMeeus;
                        deltaTstart        = -400; // 1800; // not explicitly given, but guess based on his using ChaprontFrancou which is cited elsewhere in a similar term with -391.
                        deltaTfinish        =  2150; // 1997;
                        break;
                case JPLHorizons:
                        // JPL Horizons algorithm for DeltaT
                        deltaTnDot = -25.7376; // n.dot = -25.7376 "/cy/cy
                        deltaTfunc = StelUtils::getDeltaTByJPLHorizons;
                        deltaTstart        = -2999;
                        deltaTfinish        = 1620;
                        break;
                case MeeusSimons:
                        // Meeus & Simons (2000) algorithm for DeltaT
                        deltaTnDot = -25.7376; // n.dot = -25.7376 "/cy/cy
                        deltaTfunc = StelUtils::getDeltaTByMeeusSimons;
                        deltaTstart        = 1620;
                        deltaTfinish        = 2000;
                        break;
                case ReingoldDershowitz:
                        // Reingold & Dershowitz (2002, 2007, 2018) algorithm for DeltaT
                        // FIXME: n.dot
                        deltaTnDot = -26.0; // n.dot = -26.0 "/cy/cy ???
                        deltaTfunc = StelUtils::getDeltaTByReingoldDershowitz;
                        // GZ: while not original work, it's based on Meeus and therefore the full implementation covers likewise approximately:
                        // AW: limits from 4th edition:
                        deltaTstart        = -500; //1620;
                        deltaTfinish        = 2150; //2019;
                        break;
                case MontenbruckPfleger:
                        // Montenbruck & Pfleger (2000) algorithm for DeltaT
                        // NOTE: book does not contain n.dot value
                        // FIXME: n.dot
                        deltaTnDot = -26.0; // n.dot = -26.0 "/cy/cy ???
                        deltaTfunc = StelUtils::getDeltaTByMontenbruckPfleger;
                        deltaTstart        = 1825;
                        deltaTfinish        = 2005;
                        break;
                case MorrisonStephenson2004:
                        // Morrison & Stephenson (2004, 2005) algorithm for DeltaT
                        deltaTnDot = -26.0; // n.dot = -26.0 "/cy/cy
                        deltaTfunc = StelUtils::getDeltaTByMorrisonStephenson2004;
                        deltaTstart        = -1000;
                        deltaTfinish        = 2000;
                        break;
                case Reijs:
                        // Reijs (2006) algorithm for DeltaT
                        deltaTnDot = -26.0; // n.dot = -26.0 "/cy/cy
                        deltaTfunc = StelUtils::getDeltaTByReijs;
                        deltaTstart        = -1500; // -500; // GZ: It models long-term variability, so we should reflect this. Not sure on the begin, though.
                        deltaTfinish        = 1100; // not 1620; // GZ: Not applicable for telescopic era, and better not after 1100 (pers.comm.)
                        break;
                case EspenakMeeus:
                        // Espenak & Meeus (2006) algorithm for DeltaT
                        deltaTnDot = -25.858; // n.dot = -25.858 "/cy/cy
                        deltaTfunc = StelUtils::getDeltaTByEspenakMeeus;
                        deltaTstart        = -1999;
                        deltaTfinish        = 3000;
                        break;
                case EspenakMeeusModified:
                        // Espenak & Meeus (2006) algorithm (with modified formulae) for DeltaT
                        deltaTnDot = -25.858; // n.dot = -25.858 "/cy/cy
                        deltaTfunc = StelUtils::getDeltaTByEspenakMeeusModified;
                        deltaTstart        = -1999;
                        deltaTfinish        = 3000;
                        break;
                case EspenakMeeusZeroMoonAccel:
                        // This is a trying area. Something is wrong with DeltaT, maybe ndot is still not applied correctly.
                        // Espenak & Meeus (2006) algorithm for DeltaT
                        deltaTnDot = -25.858; // n.dot = -25.858 "/cy/cy
                        deltaTdontUseMoon = true;
                        deltaTfunc = StelUtils::getDeltaTByEspenakMeeus;
                        deltaTstart        = -1999;
                        deltaTfinish        = 3000;
                        break;
                case Banjevic:
                        // Banjevic (2006) algorithm for DeltaT
                        deltaTnDot = -26.0; // n.dot = -26.0 "/cy/cy
                        deltaTfunc = StelUtils::getDeltaTByBanjevic;
                        deltaTstart        = -2020;
                        deltaTfinish        = 1620;
                        break;
                case IslamSadiqQureshi:
                        // Islam, Sadiq & Qureshi (2008 + revisited 2013) algorithm for DeltaT (6 polynomials)
                        deltaTnDot = -26.0; // n.dot = -26.0 "/cy/cy
                        deltaTfunc = StelUtils::getDeltaTByIslamSadiqQureshi;
                        deltaTdontUseMoon = true; // Seems this solutions doesn't use value of secular acceleration of the Moon
                        deltaTstart        = 1620;
                        deltaTfinish        = 2007;
                        break;
                case KhalidSultanaZaidi:
                        // M. Khalid, Mariam Sultana and Faheem Zaidi polinomial approximation of time period 1620-2013 (2014)
                        deltaTnDot = -26.0; // n.dot = -26.0 "/cy/cy
                        deltaTfunc = StelUtils::getDeltaTByKhalidSultanaZaidi;
                        deltaTdontUseMoon = true; // Seems this solutions doesn't use value of secular acceleration of the Moon
                        deltaTstart        = 1620;
                        deltaTfinish        = 2013;
                        break;
                case StephensonMorrisonHohenkerk2016:
                        deltaTnDot = -25.82; // n.dot = -25.82 "/cy/cy
                        deltaTfunc=StelUtils::getDeltaTByStephensonMorrisonHohenkerk2016;
                        deltaTstart        = -720;
                        deltaTfinish        = 2019;
                        break;
                case Henriksson2017:
                        // Henriksson solution (2017) for Schoch formula for DeltaT (1931)
                        // Source: The Acceleration of the Moon and the Universe – the Mass of the Graviton.
                        // Henriksson, G.
                        // Advances in Astrophysics, Vol. 2, No. 3, August 2017
                        // https://doi.org/10.22606/adap.2017.23004
                        deltaTnDot = -30.128; // n.dot = -30.128"/cy/cy
                        deltaTfunc = StelUtils::getDeltaTBySchoch;
                        deltaTstart        = -4000;
                        deltaTfinish        = 2000;
                        break;
                case Custom:
                        // User defined coefficients for quadratic equation for DeltaT. These can change, and we don't use the function pointer here.
                        deltaTnDot = deltaTCustomNDot; // n.dot = custom value "/cy/cy
                        deltaTfunc=Q_NULLPTR;
                        deltaTstart        = INT_MIN; // Range unknown!
                        deltaTfinish        = INT_MAX;
                        break;
                default:
                        deltaTnDot = -26.0; // n.dot = -26.0 "/cy/cy
                        deltaTfunc=Q_NULLPTR;
                        deltaTstart        = INT_MIN; // Range unknown!
                        deltaTfinish        = INT_MAX;
                        qCritical() << "StelCore: unknown DeltaT algorithm selected (" << currentDeltaTAlgorithm << ")! (setting nDot=-26., but no function!!)";
        }
        Q_ASSERT((currentDeltaTAlgorithm==Custom) || (deltaTfunc!=Q_NULLPTR));
}

//! Set the current algorithm for time correction to use
void StelCore::setCurrentDeltaTAlgorithmKey(QString key)
{
        const QMetaEnum& en = metaObject()->enumerator(metaObject()->indexOfEnumerator("DeltaTAlgorithm"));
        DeltaTAlgorithm algo = static_cast<DeltaTAlgorithm>(en.keyToValue(key.toLatin1().data()));
        if (algo<0)
        {
                qWarning() << "Unknown DeltaT algorithm: " << key << "setting \"WithoutCorrection\" instead";
                algo = WithoutCorrection;
        }
        setCurrentDeltaTAlgorithm(algo);
}

//! Get the current algorithm used by the DeltaT
QString StelCore::getCurrentDeltaTAlgorithmKey(void) const
{
        return metaObject()->enumerator(metaObject()->indexOfEnumerator("DeltaTAlgorithm")).key(currentDeltaTAlgorithm);
}

//! Get description of the current algorithm for time correction
QString StelCore::getCurrentDeltaTAlgorithmDescription(void) const
{
        // GZ remarked where more info would be desirable. Generally, a full citation and the math. term would be nice to have displayed if it's just one formula, and the range of valid dates.
        QString description;
        double jd = 0;
        QString marker;
        switch (getCurrentDeltaTAlgorithm())
        {
                case WithoutCorrection:
                        description = q_("Correction is disabled. Use only if you know what you are doing!");
                        break;
                case Schoch: // historical value.
                        description = q_("This historical formula was obtained by C. Schoch in 1931 and was used by G. Henriksson in his article <em>Einstein's Theory of Relativity Confirmed by Ancient Solar Eclipses</em> (%1). See for more info %2here%3.").arg("2009", "<a href='http://journalofcosmology.com/AncientAstronomy123.html'>", "</a>").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        break;
                case Clemence: // historical value.
                        description = q_("This empirical equation was published by G. M. Clemence in the article <em>On the system of astronomical constants</em> (%1).").arg("<a href='http://adsabs.harvard.edu/abs/1948AJ.....53..169C'>1948</a>").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        break;
                case IAU: // historical value.
                        description = q_("This formula is based on a study of post-1650 observations of the Sun, the Moon and the planets by Spencer Jones (%1) and used by Jean Meeus in his <em>Astronomical Formulae for Calculators</em>. It was also adopted in the PC program SunTracker Pro.").arg("<a href='http://adsabs.harvard.edu/abs/1939MNRAS..99..541S'>1939</a>").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        // find year of publication of AFFC
                        break;
                case AstronomicalEphemeris: // historical value.
                        description = q_("This is a slightly modified version of the IAU (1952) formula which was adopted in the <em>Astronomical Ephemeris</em> and in the <em>Canon of Solar Eclipses</em> by Mucke & Meeus (1983).").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        // TODO: expand the sentence: ... adopted ... from 19xx-19yy?
                        break;
                case TuckermanGoldstine: // historical value.
                        description = q_("The tables of Tuckerman (1962, 1964) list the positions of the Sun, the Moon and the planets at 5- and 10-day intervals from 601 BCE to 1649 CE. The same relation was also implicitly adopted in the syzygy tables of Goldstine (1973).").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        // TODO: These tables are sometimes found cited, but I have no details. Maybe add "based on ... " ?
                        break;
                case MullerStephenson:
                        description = q_("This equation was published by P. M. Muller and F. R. Stephenson in the article <em>The accelerations of the earth and moon from early astronomical observations</em> (%1).").arg("<a href='http://adsabs.harvard.edu/abs/1975grhe.conf..459M'>1975</a>").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        break;
                case Stephenson1978:
                        description = q_("This equation was published by F. R. Stephenson in the article <em>Pre-Telescopic Astronomical Observations</em> (%1).").arg("<a href='http://adsabs.harvard.edu/abs/1978tfer.conf....5S'>1978</a>").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        break;
                case SchmadelZech1979: // outdated data fit, historical value?
                        description = q_("This 12th-order polynomial equation (outdated and superseded by Schmadel & Zech (1988)) was published by L. D. Schmadel and G. Zech in the article <em>Polynomial approximations for the correction delta T E.T.-U.T. in the period 1800-1975</em> (%1) as fit through data published by Brouwer (1952).").arg("<a href='http://adsabs.harvard.edu/abs/1979AcA....29..101S'>1979</a>").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        break;
                case MorrisonStephenson1982:
                        description = q_("This algorithm was adopted in P. Bretagnon & L. Simon's <em>Planetary Programs and Tables from -4000 to +2800</em> (1986) and in the PC planetarium program RedShift.").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        break;
                case StephensonMorrison1984: // PRIMARY SOURCE
                        description = q_("This formula was published by F. R. Stephenson and L. V. Morrison in the article <em>Long-term changes in the rotation of the earth - 700 B.C. to A.D. 1980</em> (%1).").arg("<a href='http://adsabs.harvard.edu/abs/1984RSPTA.313...47S'>1984</a>").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        break;
                case StephensonHoulden:
                        description = q_("This algorithm was published by F. R. Stephenson and M. A. Houlden in the book <em>Atlas of Historical Eclipse Maps</em> (%1). This algorithm is used in the PC planetarium program Guide 7.").arg("<a href='https://assets.cambridge.org/97805212/67236/frontmatter/9780521267236_frontmatter.pdf'>1986</a>").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        break;
                case Espenak: // limited range, but wide availability?
                        description = q_("This algorithm was given by F. Espenak in his <em>Fifty Year Canon of Solar Eclipses: 1986-2035</em> (1987) and in his <em>Fifty Year Canon of Lunar Eclipses: 1986-2035</em> (1989).").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        break;
                case Borkowski: // Linked to ELP2000-85, so it's important...
                        description = q_("This formula was obtained by K.M. Borkowski (%1) from an analysis of 31 solar eclipse records dating between 2137 BCE and 1715 CE.").arg("<a href='http://adsabs.harvard.edu/abs/1988A&A...205L...8B'>1988</a>").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        break;
                case SchmadelZech1988: // data fit through Stephenson&Morrison1984, which itself is important. Unclear who uses this version?
                        description = q_("This 12th-order polynomial equation was published by L. D. Schmadel and G. Zech in the article <em>Empirical Transformations from U.T. to E.T. for the Period 1800-1988</em> (%1) as data fit through values given by Stephenson & Morrison (1984).").arg("<a href='http://adsabs.harvard.edu/abs/1988AN....309..219S'>1988</a>").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        break;
                case ChaprontTouze:
                        description = q_("This formula was adopted by M. Chapront-Touze & J. Chapront in the shortened version of the ELP 2000-85 lunar theory in their <em>Lunar Tables and Programs from 4000 B.C. to A.D. 8000</em> (1991).").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        break;
                case StephensonMorrison1995:
                        description = q_("This equation was published by F. R. Stephenson and L. V. Morrison in the article <em>Long-Term Fluctuations in the Earth's Rotation: 700 BC to AD 1990</em> (%1).").arg("<a href='http://adsabs.harvard.edu/abs/1995RSPTA.351..165S'>1995</a>").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        break;
                case Stephenson1997:
                        description = q_("F. R. Stephenson published this formula in his book <em>Historical Eclipses and Earth's Rotation</em> (%1).").arg("<a href='http://ebooks.cambridge.org/ebook.jsf?bid=CBO9780511525186'>1997</a>").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        break;
                case ChaprontMeeus:
                        description = q_("From J. Meeus, <em>Astronomical Algorithms</em> (2nd ed., 1998), and widely used. Table for 1620..2000, and includes a variant of Chapront, Chapront-Touze & Francou (1997) for dates outside 1620..2000.").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        break;
                case JPLHorizons:
                        description = q_("The JPL Solar System Dynamics Group of the NASA Jet Propulsion Laboratory use this formula in their interactive website %1JPL Horizons%2.").arg("<a href='http://ssd.jpl.nasa.gov/?horizons'>", "</a>").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        break;
                case MeeusSimons:
                        description = q_("This polynome was published by J. Meeus and L. Simons in article <em>Polynomial approximations to Delta T, 1620-2000 AD</em> (%1).").arg("<a href='http://adsabs.harvard.edu/abs/2000JBAA..110..323M'>2000</a>").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        break;
                case MontenbruckPfleger: // uninspired
                        description = q_("The fourth edition of O. Montenbruck & T. Pfleger's <em>Astronomy on the Personal Computer</em> (2000) provides simple 3rd-order polynomial data fits for the recent past.").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        break;
                case ReingoldDershowitz: //
                        description = q_("E. M. Reingold & N. Dershowitz present this polynomial data fit in <em>Calendrical Calculations</em> (4th ed. 2018) and in their <em>Calendrical Tabulations</em> (2002). It is based on Jean Meeus' <em>Astronomical Algorithms</em> (1991).").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        break;
                case MorrisonStephenson2004: // PRIMARY SOURCE
                        description = q_("This important solution was published by L. V. Morrison and F. R. Stephenson in article <em>Historical values of the Earth's clock error %1T and the calculation of eclipses</em> (%2) with addendum in (%3).").arg(QChar(0x0394)).arg("<a href='http://adsabs.harvard.edu/abs/2004JHA....35..327M'>2004</a>", "<a href='http://adsabs.harvard.edu/abs/2005JHA....36..339M'>2005</a>").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        break;
                case Reijs:
                        description = q_("From the Length of Day (LOD; as determined by Stephenson & Morrison (%2)), Victor Reijs derived a %1T formula by using a Simplex optimisation with a cosine and square function. This is based on a possible periodicy described by Stephenson (%2). See for more info %3here%4.").arg(QChar(0x0394)).arg("<a href='http://adsabs.harvard.edu/abs/2004JHA....35..327M'>2004</a>", "<a href='http://www.iol.ie/~geniet/eng/DeltaTeval.htm'>", "</a>").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        break;
                case EspenakMeeus: // GENERAL SOLUTION
                        description = q_("This solution by F. Espenak and J. Meeus, based on Morrison & Stephenson (2004) and a polynomial fit through tabulated values for 1600-2000, is used for the %1NASA Eclipse Web Site%2 and in their <em>Five Millennium Canon of Solar Eclipses: -1900 to +3000</em> (2006). This formula is also used in the solar, lunar and planetary ephemeris program SOLEX.").arg("<a href='http://eclipse.gsfc.nasa.gov/eclipse.html'>", "</a>").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        break;
                case EspenakMeeusModified: // MODIFIED SOLUTION
                        description = q_("This solution is modified from F. Espenak and J. Meeus, based on Morrison & Stephenson (2004) and a polynomial fit through tabulated values for 1600-2000. Formula for 2005-2050 is modified to match observed values and near-term predictions.").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker)).append(" <em>").append(q_("Used by default.")).append("</em>");
                        break;
                case EspenakMeeusZeroMoonAccel: // PATCHED SOLUTION. Experimental, it may not make sense to keep it in V1.0.
                        description = QString("%1 %2").arg(q_("PATCHED VERSION WITHOUT ADDITIONAL LUNAR ACCELERATION."), q_("This solution by F. Espenak and J. Meeus, based on Morrison & Stephenson (2004) and a polynomial fit through tabulated values for 1600-2000.")).append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        break;
                case Banjevic:
                        description = q_("This solution by B. Banjevic, based on Stephenson & Morrison (1984), was published in article <em>Ancient eclipses and dating the fall of Babylon</em> (%1).").arg("<a href='http://adsabs.harvard.edu/abs/2006POBeo..80..251B'>2006</a>").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        break;
                case IslamSadiqQureshi:
                        description = q_("This solution by S. Islam, M. Sadiq and M. S. Qureshi, based on Meeus & Simons (2000), was published in article <em>Error Minimization of Polynomial Approximation of DeltaT</em> (%1) and revisited by Sana Islam in 2013.").arg("<a href='http://www.ias.ac.in/article/fulltext/joaa/029/03-04/0363-0366'>2008</a>").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        break;
                case KhalidSultanaZaidi:
                        description = q_("This polynomial approximation with 0.6 seconds of accuracy by M. Khalid, Mariam Sultana and Faheem Zaidi was published in <em>Delta T: Polynomial Approximation of Time Period 1620-2013</em> (%1).").arg("<a href='https://doi.org/10.1155/2014/480964'>2014</a>").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        break;
                case StephensonMorrisonHohenkerk2016: // PRIMARY SOURCE, SEEMS VERY IMPORTANT
                        description = q_("This solution by F. R. Stephenson, L. V. Morrison and C. Y. Hohenkerk (2016) was published in <em>Measurement of the Earth’s rotation: 720 BC to AD 2015</em> (%1) and updated in <em>Addendum 2020 to 'Measurement of the Earth's Rotation: 720 BC to AD 2015'</em> (Morrison, L. V., Stephenson, F.R., Hohenkerk, C.Y. and Zawilski, M.; %2). Outside of the named range (modelled with a spline fit) it provides values from an approximate parabola.").arg("<a href='https://doi.org/10.1098/rspa.2016.0404'>2016</a>", "<a href='https://doi.org/10.1098/rspa.2020.0776'>2021</a>").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        break;
                case Henriksson2017:
                        description = q_("This solution by G. Henriksson was published in the article <em>The Acceleration of the Moon and the Universe - the Mass of the Graviton</em> (%1) and based on C. Schoch's formula (1931).").arg("<a href='https://doi.org/10.22606/adap.2017.23004'>2017</a>").append(getCurrentDeltaTAlgorithmValidRangeDescription(jd, &marker));
                        break;
                case Custom:
                        description = q_("This is a quadratic formula for calculation of %1T with coefficients defined by the user.").arg(QChar(0x0394));
                        break;
                default:
                        description = q_("Error");
        }

        // Put n-dot value info
        if (getCurrentDeltaTAlgorithm()!=WithoutCorrection)
        {
                QString accel = QString("%1\"/cy<sup>2</sup>").arg(QString::number(getDeltaTnDot(), 'f', 4));
                QString ndot  = QString("&#x1E45;");
                description.append(" " + q_("The solution's value of %1 for %2 (secular acceleration of the Moon) requires an adaptation, see Guide for details.").arg(accel, ndot));
        }

        return description;
}

QString StelCore::getCurrentDeltaTAlgorithmValidRangeDescription(const double JD, QString *marker) const
{
        QString validRange = "";
        QString validRangeAppendix = "";
        *marker = "";
        int year, month, day;

        StelUtils::getDateFromJulianDay(JD, &year, &month, &day);
        switch (currentDeltaTAlgorithm)
        {
                // These models provide extrapolated values outside their specified/recommended range.
                case WithoutCorrection:      // and
                case Schoch:                 // and
                case Clemence:               // and
                case IAU:                    // and
                case AstronomicalEphemeris:  // and
                case TuckermanGoldstine:     // and
                case StephensonHoulden:      // and
                case MullerStephenson:       // and
                case Stephenson1978:         // and
                case MorrisonStephenson1982: // and
                case StephensonMorrison1984: // and
                case Espenak:                // and
                case Borkowski:              // and
                case StephensonMorrison1995: // and
                case Stephenson1997:         // and
                case ChaprontMeeus:          // and
                case ReingoldDershowitz:     // and
                case MorrisonStephenson2004: // and
                case Reijs:                  // and
                case EspenakMeeus:           // range stated in the Canon, p. 14.  ... and
                case EspenakMeeusModified:   // the default, range stated in the Canon, p. 14.  ... and
                case EspenakMeeusZeroMoonAccel: // and
                case StephensonMorrisonHohenkerk2016: // and
                case Henriksson2017:
                        break;
                case JPLHorizons: // and
                case MeeusSimons:
                        validRangeAppendix = q_("with zero values outside this range");
                        break;
                case MontenbruckPfleger:
                        validRangeAppendix = q_("with a typical 1-second accuracy and zero values outside this range");
                        break;
                case SchmadelZech1988:
                        validRangeAppendix = q_("with a mean error of less than one second, max. error 1.9s, and values for the limit years outside this range");
                        break;
                case SchmadelZech1979:  // and
                case ChaprontTouze:     // and
                case Banjevic:          // and
                case IslamSadiqQureshi: // and
                case KhalidSultanaZaidi:
                        validRangeAppendix = q_("with values for the limit years outside this range");
                        break;
                case Custom:
                        // Valid range unknown
                        break;
        }

        if (deltaTstart > INT_MIN) // limits declared?
        {
                if (validRangeAppendix!="")
                        validRange = q_("Valid range of usage: between years %1 and %2, %3.").arg(deltaTstart).arg(deltaTfinish).arg(validRangeAppendix);
                else
                        validRange = q_("Valid range of usage: between years %1 and %2.").arg(deltaTstart).arg(deltaTfinish);
                if ((year < deltaTstart) || (deltaTfinish < year))
                        *marker = "*"; // mark "outside designed range, possibly wrong"
        }
        else
                *marker = "?"; // mark "no range given"

        return QString(" %1").arg(validRange);
}

// return if sky plus atmosphere is bright enough from sunlight so that e.g. screen labels should be rendered dark.
// DONE: Simply ask the atmosphere for its surrounding brightness
// TODO2: This could be moved to the SkyDrawer or even some GUI class, as it is used to decide a GUI thing.
bool StelCore::isBrightDaylight() const
{
        if (propMgr->getStelPropertyValue("Oculars.ocularDisplayed", true).toBool())
                return false;
        SolarSystem* ssys = GETSTELMODULE(SolarSystem);
        if (!ssys->getFlagPlanets())
                return false;
        if (!getSkyDrawer()->getFlagHasAtmosphere())
                return false;
        if (ssys->getSolarEclipseFactor(this).first<=0.01) // Total solar eclipse
                return false;

        // immediately decide upon sky background brightness...
        return (GETSTELMODULE(LandscapeMgr)->getAtmosphereAverageLuminance() > static_cast<float>(getSkyDrawer()->getDaylightLabelThreshold()));
}

double StelCore::getCurrentEpoch() const
{
        return 2000.0 + (getJD() - 2451545.0)/365.25;
}

// DE430/DE431 handling.
// NOTE: When DE431 is not available, DE430 installed, but date outside, de430IsActive() may be true but computations still go back to VSOP!
// To test whether DE43x is really currently in use, test (EphemWrapper::use_de430(jd) || EphemWrapper::use_de431(jd))

bool StelCore::de430IsAvailable()
{
        return de430Available;
}

bool StelCore::de431IsAvailable()
{
        return de431Available;
}

bool StelCore::de430IsActive()
{
        return de430Active;
}

bool StelCore::de431IsActive()
{
        return de431Active;
}

void StelCore::setDe430Active(bool status)
{
        de430Active = de430Available && status;
}

void StelCore::setDe431Active(bool status)
{
        de431Active = de431Available && status;
}


bool StelCore::de440IsAvailable()
{
        return de440Available;
}

bool StelCore::de441IsAvailable()
{
        return de441Available;
}

bool StelCore::de440IsActive()
{
        return de440Active;
}

bool StelCore::de441IsActive()
{
        return de441Active;
}

void StelCore::setDe440Active(bool status)
{
        de440Active = de440Available && status;
}

void StelCore::setDe441Active(bool status)
{
        de441Active = de441Available && status;
}

void StelCore::initEphemeridesFunctions()
{
        QSettings* conf = StelApp::getInstance().getSettings();

        QString de430ConfigPath = conf->value("astro/de430_path").toString();
        QString de431ConfigPath = conf->value("astro/de431_path").toString();
        QString de440ConfigPath = conf->value("astro/de440_path").toString();
        QString de441ConfigPath = conf->value("astro/de441_path").toString();

        QString de430FilePath;
        QString de431FilePath;
        QString de440FilePath;
        QString de441FilePath;

        //<-- DE430 -->
        if(de430ConfigPath.remove(QChar('"')).isEmpty())
                de430FilePath = StelFileMgr::findFile("ephem/" + QString(DE430_FILENAME), StelFileMgr::File);
        else
                de430FilePath = StelFileMgr::findFile(de430ConfigPath, StelFileMgr::File);

        de430Available=!de430FilePath.isEmpty();
        if(de430Available)
        {
                qDebug() << "DE430 at: " << de430FilePath;
                EphemWrapper::init_de430(de430FilePath.toStdString().c_str());
        }
        setDe430Active(de430Available && conf->value("astro/flag_use_de430", false).toBool());

        //<-- DE431 -->
        if(de431ConfigPath.remove(QChar('"')).isEmpty())
                de431FilePath = StelFileMgr::findFile("ephem/" + QString(DE431_FILENAME), StelFileMgr::File);
        else
                de431FilePath = StelFileMgr::findFile(de431ConfigPath, StelFileMgr::File);

        de431Available=!de431FilePath.isEmpty();
        if(de431Available)
        {
                qDebug() << "DE431 at: " << de431FilePath;
                EphemWrapper::init_de431(de431FilePath.toStdString().c_str());
        }
        setDe431Active(de431Available && conf->value("astro/flag_use_de431", false).toBool());

        //<-- DE440 -->
        if(de440ConfigPath.remove(QChar('"')).isEmpty())
                de440FilePath = StelFileMgr::findFile("ephem/" + QString(DE440_FILENAME), StelFileMgr::File);
        else
                de440FilePath = StelFileMgr::findFile(de440ConfigPath, StelFileMgr::File);

        de440Available=!de440FilePath.isEmpty();
        if(de440Available)
        {
                qDebug() << "DE440 at: " << de440FilePath;
                EphemWrapper::init_de440(de440FilePath.toStdString().c_str());
        }
        setDe440Active(de440Available && conf->value("astro/flag_use_de440", false).toBool());

        //<-- DE441 -->
        if(de441ConfigPath.remove(QChar('"')).isEmpty())
                de441FilePath = StelFileMgr::findFile("ephem/" + QString(DE441_FILENAME), StelFileMgr::File);
        else
                de441FilePath = StelFileMgr::findFile(de441ConfigPath, StelFileMgr::File);

        de441Available=!de441FilePath.isEmpty();
        if(de441Available)
        {
                qDebug() << "DE441 at: " << de441FilePath;
                EphemWrapper::init_de441(de441FilePath.toStdString().c_str());
        }
        setDe441Active(de441Available && conf->value("astro/flag_use_de441", false).toBool());
}

// Methods for finding constellation from J2000 position.
typedef struct iau_constline{
        double RAlow;  // low value of 1875.0 right ascension segment, HH.dddd
        double RAhigh; // high value of 1875.0 right ascension segment, HH.dddd
        double decLow; // declination 1875.0 of southern border, DD.dddd
        QString constellation; // 3-letter code of constellation
} iau_constelspan;

static QVector<iau_constelspan> iau_constlineVec;
static bool iau_constlineVecInitialized=false;

// File iau_constellations_spans.dat is converted from file data.dat from ADC catalog VI/42.
// We converted back to HH:MM:SS format to avoid the inherent rounding errors present in that file (Bug LP:#1690615).
QString StelCore::getIAUConstellation(const Vec3d &positionEqJnow) const
{
        // Precess positionJ2000 to 1875.0
        const Vec3d pos1875=j2000ToJ1875(equinoxEquToJ2000(positionEqJnow, RefractionOff));
        double RA1875;
        double dec1875;
        StelUtils::rectToSphe(&RA1875, &dec1875, pos1875);
        RA1875 *= 12./M_PI; // hours
        if (RA1875 <0.) RA1875+=24.;
        dec1875 *= M_180_PI; // degrees
        Q_ASSERT(RA1875>=0.0);
        Q_ASSERT(RA1875<=24.0);
        Q_ASSERT(dec1875<=90.0);
        Q_ASSERT(dec1875>=-90.0);

        // read file into structure.
        if (!iau_constlineVecInitialized)
        {
                //struct iau_constline line;
                QFile file(StelFileMgr::findFile("data/constellations_spans.dat"));

                if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
                {
                        qWarning() << "IAU constellation line data file data/constellations_spans.dat not found.";
                        return "err";
                }
                iau_constelspan span;
                static const QRegularExpression emptyLine("^\\s*$");
                static const QRegularExpression spaceRe("\\s+");
                QTextStream in(&file);
                while (!in.atEnd())
                {
                        // Build list of entries. The checks can certainly become more robust. Actually the file must have 4-part lines.
                        QString line = in.readLine();
                        if (line.length()==0) continue;
                        if (emptyLine.match(line).hasMatch()) continue;
                        if (line.at(0)=='#') continue; // skip comment lines.
                        //QStringList list = line.split(QRegularExpression("\\b\\s+\\b"));
                        QStringList list = line.trimmed().split(spaceRe);
                        if (list.count() != 4)
                        {
                                qWarning() << "IAU constellation file constellations_spans.dat has bad line:" << line << "with" << list.count() << "elements";
                                continue;
                        }
                        //qDebug() << "Creating span for decl=" << list.at(2) << " from RA=" << list.at(0) << "to" << list.at(1) << ": " << list.at(3);
                        QStringList numList=list.at(0).split(QString(":"));
                        span.RAlow= atof(numList.at(0).toLatin1()) + atof(numList.at(1).toLatin1())/60. + atof(numList.at(2).toLatin1())/3600.;
                        numList=list.at(1).split(QString(":"));
                        span.RAhigh=atof(numList.at(0).toLatin1()) + atof(numList.at(1).toLatin1())/60. + atof(numList.at(2).toLatin1())/3600.;
                        numList=list.at(2).split(QString(":"));
                        span.decLow=atof(numList.at(0).toLatin1());
                        if (span.decLow<0.0)
                                span.decLow -= atof(numList.at(1).toLatin1())/60.;
                        else
                                span.decLow += atof(numList.at(1).toLatin1())/60.;
                        span.constellation=list.at(3);
                        iau_constlineVec.append(span);
                }
                file.close();
                iau_constlineVecInitialized=true;
        }

        // iterate through vector, find entry where declination is lower.
        int entry=0;
        while (iau_constlineVec.at(entry).decLow > dec1875)
                entry++;
        while (entry<iau_constlineVec.size())
        {
                while (iau_constlineVec.at(entry).RAhigh <= RA1875)
                        entry++;
                while (iau_constlineVec.at(entry).RAlow >= RA1875)
                        entry++;
                if (iau_constlineVec.at(entry).RAhigh > RA1875)
                        return iau_constlineVec.at(entry).constellation;
                else
                        entry++;
        }
        qDebug() << "getIAUconstellation error: Cannot determine, algorithm failed.";
        return "(?)";
}

// NELM = naked-eye limiting magnitude
int StelCore::nelmToBortleScaleIndex(const float nelm)
{
        // Ref: Bortle, John E. (February 2001). "Gauging Light Pollution: The Bortle Dark-Sky Scale".
        //  Sky & Telescope. Sky Publishing Corporation.
        // https://skyandtelescope.org/astronomy-resources/light-pollution-and-astronomy-the-bortle-dark-sky-scale/
        if(nelm < 4.0) return 9;
        if(nelm < 4.5) return 8;
        if(nelm < 5.0) return 7;
        if(nelm < 5.5) return 6;
        if(nelm < 6.0) return 5;
        if(nelm < 6.5) return 4;
        if(nelm < 7.0) return 3;
        if(nelm < 7.5) return 2;
        return 1;
}

float StelCore::bortleScaleIndexToNELM(const int index)
{
        // This is kind of inverse of nelmToBortleScaleIndex(), where the "representative NELM" is chosen to be
        // the middle of the interval of the NELM values for the inner indices (2-8), and the same distance from
        // the boundary for outer indices (1 and 9).
        switch(index)
        {
        case 1: return 7.75;
        case 2: return 7.25;
        case 3: return 6.75;
        case 4: return 6.25;
        case 5: return 5.75;
        case 6: return 5.25;
        case 7: return 4.75;
        case 8: return 4.25;
        case 9: return 3.75;
        default:
                        qWarning().nospace() << "Bortle scale index " << index << " out of range";
                        return 0; // Let the problem be visible
        }
}

float StelCore::luminanceToNELM(const float luminance)
{
        // Ref: Schaefer, B. E.. "Telescopic limiting magnitudes". Astronomical Society of the Pacific,
        //  Publications (ISSN 0004-6280), vol. 102, Feb. 1990, p. 212-229.
        // http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1990PASP..102..212S
        //
        // Using formula (18), assuming observer's acuity Fₛ=1 (as suggested in the text as "typical observer"),
        // absorption term kᵥ=0.3 (as suggested for "typical weather"), coefficient for Bₛ is adjusted to take
        // the value in cd/m².
        //
        return 8.32f - 2.17147240951626f*std::log(1 + 88.5588612190873f*std::sqrt(luminance));
}

float StelCore::nelmToLuminance(const float nelm)
{
        // This is just the inverse of luminanceToNELM()
        const auto toSquare = std::exp(3.8315015947420905f-0.46051701859880895f*nelm) - 1;
        return toSquare*toSquare*0.0001275075653676456f;
}

Vec3d StelCore::getMouseJ2000Pos() const
{
        const StelProjectorP prj = getProjection(StelCore::FrameJ2000, StelCore::RefractionAuto);
        float ppx = static_cast<float>(getCurrentStelProjectorParams().devicePixelsPerPixel);

        QPoint p = StelMainView::getInstance().getMousePos(); // get screen coordinates of mouse cursor
        Vec3d mousePosition;
        const float wh = prj->getViewportWidth()*0.5f; // get half of width of the screen
        const float hh = prj->getViewportHeight()*0.5f; // get half of height of the screen
        const float mx = p.x()*ppx-wh; // point 0 in center of the screen, axis X directed to right
        const float my = p.y()*ppx-hh; // point 0 in center of the screen, axis Y directed to bottom
        // calculate position of mouse cursor via position of center of the screen (and invert axis Y)
        // If coordinates are invalid, don't draw them.
        bool coordsValid = prj->unProject(static_cast<double>(prj->getViewportPosX()+wh+mx), static_cast<double>(prj->getViewportPosY()+hh+1-my), mousePosition);
        if (coordsValid)
        { // Nick Fedoseev patch
                Vec3d win;
                prj->project(mousePosition,win);
                float dx = prj->getViewportPosX()+wh+mx - static_cast<float>(win.v[0]);
                float dy = prj->getViewportPosY()+hh+1-my - static_cast<float>(win.v[1]);
                prj->unProject(static_cast<double>(prj->getViewportPosX()+wh+mx+dx), static_cast<double>(prj->getViewportPosY()+hh+1-my+dy), mousePosition);
        }
//        if (getUseAberration() && getCurrentPlanet())
//        {
//                Vec3d vel=getCurrentPlanet()->getHeliocentricEclipticVelocity();
//                vel=StelCore::matVsop87ToJ2000*vel * getAberrationFactor()*(AU/(86400.0*SPEED_OF_LIGHT));
//                mousePosition-=vel;
//                mousePosition.normalize();
//        }
        return mousePosition;
}

QByteArray StelCore::getAberrationShader() const
{
        return 1+R"(
uniform vec3 STELCORE_currentPlanetHeliocentricEclipticVelocity;
// objectDir points to the object as viewed from its comoving frame.
// Return value represents the apparent direction to this object from a frame
// that moves with respect to the object at slightly relativistic speeds (v<0.1c).
// Relative error in aberration angle is about 0.5v/c.
vec3 applyAberrationToObject(vec3 objectDir)
{
        vec3 velocity = STELCORE_currentPlanetHeliocentricEclipticVelocity;
        return normalize(objectDir + velocity);
}
// viewDir is the direction where the object appears to be when viewed from a
// frame that moves with respect to it at slightly relativistic speeds (v<0.1c).
// Return value represents the direction to the object as viewed from its comoving frame.
// Relative error in aberration angle is about 0.5v/c.
vec3 applyAberrationToViewDir(vec3 viewDir)
{
        vec3 velocity = STELCORE_currentPlanetHeliocentricEclipticVelocity;
        return normalize(viewDir - velocity);
}
)";
}

void StelCore::setAberrationUniforms(QOpenGLShaderProgram& program) const
{
        Vec3d velocity;
        if(getUseAberration())
        {
                const auto p = getCurrentPlanet();
                const auto hev = p->getHeliocentricEclipticVelocity();
                velocity = StelCore::matVsop87ToJ2000 * hev;
                velocity *= getAberrationFactor() * (AU/(86400.0*SPEED_OF_LIGHT));
        }
        else
        {
                velocity = Vec3d(0,0,0);
        }
        program.setUniformValue("STELCORE_currentPlanetHeliocentricEclipticVelocity", velocity.toQVector());
}

Stellarium / stellarium / 4105865515

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