Merge lp:~i-martividal/stellarium/Observability-1.1.0 into lp:stellarium

[Ivan Marti-Vidal]

Dear all,

Here you have the revised version of Observability. Now, the dates of Full Moon are computed by solving the Ecliptic longitude to be 180 deg away from the Sun. It's faster and much more precise.

I've also solved a few minor bugs and added the possibility to set the altitude of the horizon manually. After discussion with some colleagues, I think that this feature may be quite useful for some people (for instance, those who want to know when will an object reach a given minimum altitude, if they want to take good pictures).

  Best Wishes,

       Ivan

[Alexander Wolf (alexwolf)]

review: Approve

=== modified file 'plugins/Observability/CMakeLists.txt'
--- plugins/Observability/CMakeLists.txt	2012-12-09 19:10:43 +0000
+++ plugins/Observability/CMakeLists.txt	2013-01-17 13:33:22 +0000
@@ -1,4 +1,4 @@
-SET(OBSERVABILITY_VERSION "1.0.3")
+SET(OBSERVABILITY_VERSION "1.1.0")
 
 IF(APPLE)
    SET(CMAKE_INSTALL_PREFIX $ENV{HOME}/Library/Application\ Support/Stellarium)

=== modified file 'plugins/Observability/src/Observability.cpp'
--- plugins/Observability/src/Observability.cpp	2012-09-23 12:08:15 +0000
+++ plugins/Observability/src/Observability.cpp	2013-01-17 13:33:22 +0000
@@ -91,6 +91,7 @@
 	MoonPerilune = 0.0024236308; // Smallest Earth-Moon distance (in AU). 
 	nextFullMoon = 0.0;
 	prevFullMoon = 0.0;
+	RefracHoriz = 0.0;   // Geometric altitude at refraction-corrected horizon. 
 	selName = "";
 
 
@@ -122,6 +123,9 @@
 	if (!conf->contains("Sun_Altitude"))
 		conf->setValue("Sun_Altitude", 12);
 
+	if (!conf->contains("Horizon_Altitude"))
+		conf->setValue("Horizon_Altitude", 0);
+
 	if (!conf->contains("show_FullMoon"))
 		conf->setValue("show_FullMoon", true);
 
@@ -135,7 +139,9 @@
 	// Load settings from main config file
 	fontSize = conf->value("font_size",15).toInt();
 	iAltitude = conf->value("Sun_Altitude",12).toInt();
+	iHorizAltitude = conf->value("Horizon_Altitude",0).toInt();
 	AstroTwiAlti = -((double) iAltitude)/Rad2Deg ;
+	HorizAlti = ((double) iHorizAltitude)/Rad2Deg ;
 	font.setPixelSize(fontSize);
 	QString fontColorStr = conf->value("font_color", "0,0.5,1").toString();
 	fontColor = StelUtils::strToVec3f(fontColorStr);
@@ -264,7 +270,11 @@
 	double currheight = (6371.+(core->getCurrentLocation().altitude)/1000.)/UA;
 	double currJD = core->getJDay();
 	double currJDint;
+//	GMTShift = StelUtils::getGMTShiftFromQT(currJD)/24.0;
 	GMTShift = StelApp::getInstance().getLocaleMgr().getGMTShift(currJD)/24.0;
+
+//	qDebug() << QString("%1%2 ").arg(GMTShift);
+
 	double currLocalT = 24.*modf(currJD + GMTShift,&currJDint);
 
 	int auxm, auxd, auxy;
@@ -302,6 +312,28 @@
 		ObserverLoc[2] = currheight*std::sin(currlat);
 	};
 
+
+
+// Add refraction, if necessary:
+	Vec3d TempRefr;	
+	TempRefr[0] = std::cos(HorizAlti);  
+	TempRefr[1] = 0.0; 
+	TempRefr[2] = std::sin(HorizAlti);  
+	Vec3d CorrRefr = core->altAzToEquinoxEqu(TempRefr,StelCore::RefractionAuto);
+	TempRefr = core->equinoxEquToAltAz(CorrRefr,StelCore::RefractionOff);
+	double RefracAlt = std::asin(TempRefr[2]);
+
+	if (std::abs(RefracHoriz-RefracAlt)>2.91e-4)  // Diference larger than 1 arcminute.
+	{   // Configuration for refraction changed notably:
+		RefracHoriz = RefracAlt;
+		configChanged = true;
+		souChanged = true;
+	};
+
+
+
+
+
 // If we have changed latitude (or year), we update the vector of Sun's hour 
 // angles at twilight, and re-compute Sun/Moon ephemeris (if selected):
 	if (locChanged || yearChanged || configChanged) 
@@ -409,7 +441,7 @@
 /////////////////////////////////////////////////////////////////
 // NOW WE COMPUTE RISE/SET/TRANSIT TIMES FOR THE CURRENT DAY:
 	double currH = HourAngle(mylat,alti,selDec);
-	horizH = HourAngle(mylat,0.0,selDec);
+	horizH = HourAngle(mylat,RefracHoriz,selDec);
 	QString RS1, RS2, Cul; // strings with Rise/Set/Culmination times
 	double Rise, Set; // Actual Rise/Set times (in GMT).
 	int d1,m1,s1,d2,m2,s2,dc,mc,sc; // Integers for the time spans in hh:mm:ss.
@@ -490,7 +522,7 @@
 			};				
 		}
 		else { // The source is either circumpolar or never rises:
-			(alti>0.0)? RS1 = q_("Circumpolar."): RS1 = q_("No rise.");
+			(alti>RefracHoriz)? RS1 = q_("Circumpolar."): RS1 = q_("No rise.");
 			RS2 = "";
 		};
 
@@ -502,8 +534,8 @@
 		transit = LocPos[1]<0.0;
 	};
 
-	if (culmAlt<halfpi) { // Source can be observed.
-		double altiAtCulmi = Rad2Deg*(halfpi-culmAlt);
+	if (culmAlt<halfpi-RefracHoriz) { // Source can be observed.
+		double altiAtCulmi = Rad2Deg*(halfpi-culmAlt-RefracHoriz);
 		double2hms(TFrac*currH,dc,mc,sc);
 
 //		String with the time span for culmination:	
@@ -516,7 +548,7 @@
 		else {
                         double2hms(toUnsignedRA(currLocalT-TFrac*currH+12.),ephHour,ephMinute,ephSecond);
 			CulmTime = QString("%1:%2").arg(ephHour).arg(ephMinute,2,10,QLatin1Char('0'));
-			Cul = q_("Culminated at %1 (%2 ago) at %3 deg.").arg(CulmTime).arg(Cul).arg(altiAtCulmi,0,'f',1);
+			Cul = q_("Transit at %1 (%2 ago) at %3 deg.").arg(CulmTime).arg(Cul).arg(altiAtCulmi,0,'f',1);
 		};
 	};
 
@@ -540,7 +572,7 @@
 			PlanetRADec(core);} // Re-compute ephemeris.
 
 		else { // Object is fixed on the sky.
-			double auxH = HourAngle(mylat,0.0,selDec);
+			double auxH = HourAngle(mylat,RefracHoriz,selDec);
 			double auxSidT1 = toUnsignedRA(selRA - auxH); 
 			double auxSidT2 = toUnsignedRA(selRA + auxH); 
 			for (int i=0;i<nDays;i++) {
@@ -556,7 +588,7 @@
 		if ((souChanged || locChanged || yearChanged)) {
 			bestNight=""; ObsRange = "";
 
-			if (culmAlt>=halfpi) { // Source cannot be seen.
+			if (culmAlt>=halfpi-RefracHoriz) { // Source cannot be seen.
 				ObsRange = q_("Source is not observable.");
 				AcroCos = q_("No Acronychal nor Cosmical rise/set.");
 			}
@@ -593,11 +625,11 @@
 					QString AcroRiseStr, AcroSetStr;
 					QString CosmRiseStr, CosmSetStr;
 
-					AcroRiseStr = (selRise>0)?CalenDate(selRise):q_("N/A");
-					AcroSetStr = (selSet>0)?CalenDate(selSet):q_("N/A");
+					AcroRiseStr = (selRise>0)?CalenDate(selRise):q_("None");
+					AcroSetStr = (selSet>0)?CalenDate(selSet):q_("None");
 
-					CosmRiseStr = (selRise2>0)?CalenDate(selRise2):q_("N/A");
-					CosmSetStr = (selSet2>0)?CalenDate(selSet2):q_("N/A");
+					CosmRiseStr = (selRise2>0)?CalenDate(selRise2):q_("None");
+					CosmSetStr = (selSet2>0)?CalenDate(selSet2):q_("None");
 
 					AcroCos = (Acro==3 || Acro==1)?QString("%1: %2/%3.").arg(q_("Acronychal rise/set")).arg(AcroRiseStr).arg(AcroSetStr):q_("No Acronychal rise/set.");
 					AcroCos += (Acro==3 || Acro==2)?QString(" %1: %2/%3.").arg(q_("Cosmical rise/set")).arg(CosmRiseStr).arg(CosmSetStr):QString(" %1").arg(q_("No Cosmical rise/set."));
@@ -829,7 +861,7 @@
 
 	for (int i=0;i<nDays;i++) {
 		getPlanetCoords(core,yearJD[i],ObjectRA[i],ObjectDec[i],false);
-		TempH = HourAngle(mylat,0.0,ObjectDec[i]);
+		TempH = HourAngle(mylat,RefracHoriz,ObjectDec[i]);
 		ObjectH0[i] = TempH;
 		ObjectSidT[0][i] = toUnsignedRA(ObjectRA[i]-TempH);
 		ObjectSidT[1][i] = toUnsignedRA(ObjectRA[i]+TempH);
@@ -884,7 +916,7 @@
 
 	for (int i=0; i<nDays; i++) {
 		TempH = HourAngle(mylat,AstroTwiAlti,SunDec[i]);
-		TempH00 = HourAngle(mylat,0.0,SunDec[i]);
+		TempH00 = HourAngle(mylat,RefracHoriz,SunDec[i]);
 		if (TempH>0.0) {
 			SunSidT[0][i] = toUnsignedRA(SunRA[i]-TempH*(1.00278));
 			SunSidT[1][i] = toUnsignedRA(SunRA[i]+TempH*(1.00278));}
@@ -1026,7 +1058,7 @@
 //////////////////////////
 // Get the coordinates of Sun or Moon for a given JD:
 // getBack controls whether Earth and Moon must be returned to their original positions after computation.
-void Observability::getSunMoonCoords(StelCore *core, double JD, double &RASun, double &DecSun, double &RAMoon, double &DecMoon, bool getBack) //, Vec3d &AltAzVector)
+void Observability::getSunMoonCoords(StelCore *core, double JD, double &RASun, double &DecSun, double &RAMoon, double &DecMoon, double &EclLon, bool getBack) //, Vec3d &AltAzVector)
 {
 
 	if (getBack) // Return the Moon and Earth to their current position:
@@ -1056,6 +1088,8 @@
 		Pos1 = myMoon->getHeliocentricEclipticPos();
 		Pos2 = (core->j2000ToEquinoxEqu(LocTrans*Pos1))-RotObserver;
 
+                EclLon = Pos1[0]*Pos0[1] - Pos1[1]*Pos0[0];
+
 		toRADec(Pos2,RAMoon,DecMoon);
 	};
 }
@@ -1144,10 +1178,10 @@
 
 	int Niter = 100;
 	int i;
-	double Hhoriz, RA, Dec, RAS, DecS, TempH, jd1, tempEphH, currSidT;
+	double Hhoriz, RA, Dec, RAS, DecS, TempH, jd1, tempEphH, currSidT, EclLon;
 	Vec3d Observer;
 
-	Hhoriz = HourAngle(mylat,0.0,selDec);
+	Hhoriz = HourAngle(mylat,RefracHoriz,selDec);
 	bool raises = Hhoriz > 0.0;
 
 
@@ -1187,7 +1221,7 @@
 
 		toRADec(Pos2,RA,Dec);
 		Vec3d MoonAltAz = core->equinoxEquToAltAz(Pos2,StelCore::RefractionOff);
-		raised = MoonAltAz[2] > 0.0;
+		raised = MoonAltAz[2] > RefracHoriz;
 
 // Initial guesses of rise/set/transit times.
 // They are called 'Moon', but are also used for the Sun or planet:
@@ -1215,7 +1249,7 @@
 	
 				if (Kind<3)
 				{
-					getSunMoonCoords(core,jd1,RAS,DecS,RA,Dec,false);
+					getSunMoonCoords(core,jd1,RAS,DecS,RA,Dec,EclLon,false);
 				} else
 				{
 					getPlanetCoords(core,jd1,RA,Dec,false);
@@ -1229,7 +1263,7 @@
 				Hcurr -= (Hcurr>12.)?24.0:0.0;
 
 	// H at horizon for mod. coordinates:
-				Hhoriz = HourAngle(mylat,0.0,Dec);
+				Hhoriz = HourAngle(mylat,RefracHoriz,Dec);
 	// Compute eph. times for mod. coordinates:
 				TempH = (-Hhoriz-Hcurr)*TFrac;
 				if (raised==false) TempH += (TempH<0.0)?24.0:0.0;
@@ -1250,7 +1284,7 @@
 
                 	        if (Kind<3)
 				{
-                                	getSunMoonCoords(core,jd1,RAS,DecS,RA,Dec,false);
+                                	getSunMoonCoords(core,jd1,RAS,DecS,RA,Dec,EclLon,false);
                         	} else
                         	{
                                 	getPlanetCoords(core,jd1,RA,Dec,false);
@@ -1263,7 +1297,7 @@
 				Hcurr -= (raised)?24.:0.;
 				Hcurr += (Hcurr<-12.)?24.0:0.0;
 	// H at horizon for mod. coordinates:
-				Hhoriz = HourAngle(mylat,0.0,Dec);
+				Hhoriz = HourAngle(mylat,RefracHoriz,Dec);
 	// Compute eph. times for mod. coordinates:
 				TempH = (Hhoriz-Hcurr)*TFrac;
 				if (raised==false) TempH -= (TempH>0.0)?24.0:0.0;
@@ -1290,7 +1324,7 @@
 
                 	        if (Kind<3)
                        		{
-                                	getSunMoonCoords(core,jd1,RAS,DecS,RA,Dec,false);
+                                	getSunMoonCoords(core,jd1,RAS,DecS,RA,Dec,EclLon,false);
                         	} else
                         	{
                                 	getPlanetCoords(core,jd1,RA,Dec,false);
@@ -1316,6 +1350,9 @@
 
 //		qDebug() << q_("%1").arg(MoonCulm,0,'f',5);
 
+
+	lastJDMoon = myJD;
+
 	}; // Comes from if (std::abs(myJD-lastJDMoon)>JDsec || LastObject!=Kind)
 
 
@@ -1341,10 +1378,10 @@
 	// Improve the estimate iteratively (Secant method over Lunar-phase vs. time):
 
 			dT = 0.1/1440.; // 6 seconds. Our time span for the finite-difference derivative estimate.
-			double Deriv1, Deriv2; // Variables for temporal use.
-			double Sec1, Sec2, SecMed, Temp1, Temp2; // Variables for temporal use.
+//			double Deriv1, Deriv2; // Variables for temporal use.
+			double Sec1, Sec2, Temp1, Temp2; // Variables for temporal use.
 			double iniEst1, iniEst2;  // JD values that MUST include the solution within them.
-			double Phase1, Phase2, PhaseMed;
+			double Phase1;
 
 			for (int j=0; j<2; j++) 
 			{ // Two steps: one for the previos Full Moon and the other for the next one.
@@ -1355,55 +1392,40 @@
 				Sec1 = iniEst1; // TempFullMoon - 0.05*MoonT; // Initial estimates of Full-Moon dates
 				Sec2 = iniEst2; // TempFullMoon + 0.05*MoonT; 
 
+				getSunMoonCoords(core,Sec1,RAS,DecS,RA,Dec,EclLon,false);
+				Temp1 = EclLon; //Lambda(RA,Dec,RAS,DecS);
+				getSunMoonCoords(core,Sec2,RAS,DecS,RA,Dec,EclLon,false);
+				Temp2 = EclLon; //Lambda(RA,Dec,RAS,DecS);
+
+
 				for (int i=0; i<100; i++) // A limit of 100 iterations.
 				{
-					getSunMoonCoords(core,Sec1+dT/2.,RAS,DecS,RA,Dec,false);
-					Temp1 = Lambda(RA,Dec,RAS,DecS);
-					getSunMoonCoords(core,Sec1-dT/2.,RAS,DecS,RA,Dec,false);
-					Temp2 = Lambda(RA,Dec,RAS,DecS);
-
-					Deriv1 = (Temp1-Temp2)/dT;
-					Phase1 =  (Temp1+Temp2)/2.;
-
-					getSunMoonCoords(core,Sec2+dT/2.,RAS,DecS,RA,Dec,false);
-					Temp1 = Lambda(RA,Dec,RAS,DecS);
-					getSunMoonCoords(core,Sec2-dT/2.,RAS,DecS,RA,Dec,false);
-					Temp2 = Lambda(RA,Dec,RAS,DecS);
-
-					Deriv2 = (Temp1-Temp2)/dT;
-					Phase2 =  (Temp1+Temp2)/2.;
-
-					SecMed = (Sec2+Sec1)/2.;
-					getSunMoonCoords(core,SecMed+dT/2.,RAS,DecS,RA,Dec,false);
-					Temp1 = Lambda(RA,Dec,RAS,DecS);
-					getSunMoonCoords(core,SecMed-dT/2.,RAS,DecS,RA,Dec,false);
-					Temp2 = Lambda(RA,Dec,RAS,DecS);
-
-				//	DerivMed = (Temp1-Temp2)/dT;
-					PhaseMed =  (Temp1+Temp2)/2.;
-
-					Temp1 = Sec2 - Deriv2*(Sec2-Sec1)/(Deriv2-Deriv1);
-
-					// Force the solution to fall within the range of good possible solutions:
-					if (Temp1 < iniEst1 || Temp1 > iniEst2) 
-					{
-						if (Phase1>Phase2)
-						{
-							Sec2 = (Phase2 > PhaseMed)?Sec2:SecMed;
-						} else 
-						{
-							Sec1 = Sec2;
-							Sec2 = (Phase1>PhaseMed)?Sec1:SecMed;
-						};
-					} else
-					{
-						Sec1 = Sec2; Sec2 = Temp1;
-					};
-
-					if (std::abs(Sec2-Sec1) < 10.*dT) {TempFullMoon = Temp1; break;}  // 1 minute accuracy. Convergence.
-
+                                        Phase1 = (Sec2-Sec1)/(Temp1-Temp2)*Temp1+Sec1;
+					getSunMoonCoords(core,Phase1,RAS,DecS,RA,Dec,EclLon,false);
+
+                                        if (Temp1*EclLon < 0.0) 
+					{
+						Sec2 = Phase1;
+						Temp2 = EclLon;
+					} else {
+						Sec1 = Phase1;
+						Temp1 = EclLon;
+
+					};
+
+				//	qDebug() << QString("%1 %2 %3 %4 ").arg(Sec1).arg(Sec2).arg(Temp1).arg(Temp2);	
+
+
+					if (std::abs(Sec2-Sec1) < 10.*dT)  // 1 minute accuracy; convergence.
+					{
+						TempFullMoon = (Sec1+Sec2)/2.;
+				//		qDebug() << QString("%1%2 ").arg(TempFullMoon);	
+						break;
+					};
+					
 				};
 
+
 				if (TempFullMoon > myJD) 
 				{
 					nextFullMoon = TempFullMoon;
@@ -1473,14 +1495,12 @@
 // Return the Moon and Earth to its current position:
 	if (Kind<3)
 	{
-		getSunMoonCoords(core,myJD,RAS,DecS,RA,Dec,true);
+		getSunMoonCoords(core,myJD,RAS,DecS,RA,Dec,EclLon,true);
 	} else
 	{
                 getPlanetCoords(core,myJD,RA,Dec,true);
 	};
 
-	lastJDMoon = myJD;
-
 
 	return raises;
 }
@@ -1520,6 +1540,7 @@
 	// Set defaults
 	conf->setValue("font_size", 15);
 	conf->setValue("Sun_Altitude", 12);
+	conf->setValue("Horizon_Altitude", 0);
 	conf->setValue("font_color", "0,0.5,1");
 	conf->setValue("show_AcroCos", true);
 	conf->setValue("show_Good_Nights", true);
@@ -1552,7 +1573,11 @@
 
 	iAltitude = conf->value("Sun_Altitude", 12).toInt();
 	AstroTwiAlti  = -((double)iAltitude)/Rad2Deg ;
+
+	iHorizAltitude = conf->value("Horizon_Altitude", 0).toInt();
+	HorizAlti = ((double)iHorizAltitude)/Rad2Deg ;
 	
+
 	conf->endGroup();
 }
 
@@ -1564,6 +1589,7 @@
 	conf->beginGroup("Observability");
 	conf->setValue("font_size", fontSize);
 	conf->setValue("Sun_Altitude", iAltitude);
+	conf->setValue("Horizon_Altitude", iHorizAltitude);
 	conf->setValue("font_color", fontColorStr);
 	conf->setValue("show_AcroCos", show_AcroCos);
 	conf->setValue("show_Good_Nights", show_Good_Nights);
@@ -1623,6 +1649,12 @@
 	return iAltitude;
 }
 
+int Observability::getHorizAltitude(void)
+{
+	return iHorizAltitude;
+}
+
+
 void Observability::setFontColor(int color, int value)
 {
 	float fValue = (float)(value) / 100.; 
@@ -1641,6 +1673,13 @@
 	configChanged = true;
 }
 
+void Observability::setHorizAltitude(int value)
+{
+	HorizAlti = ((double) value)/Rad2Deg ;
+	iHorizAltitude = value;
+	configChanged = true;
+}
+
 
 ///  END OF STUFF FOR THE GUI CONFIG.
 ///////////////////////////////

=== modified file 'plugins/Observability/src/Observability.hpp'
--- plugins/Observability/src/Observability.hpp	2012-08-29 13:18:51 +0000
+++ plugins/Observability/src/Observability.hpp	2013-01-17 13:33:22 +0000
@@ -71,6 +71,9 @@
 	//! Set the Sun altitude at twilight:
 	void setSunAltitude(int);
 
+	//! Set the Sun altitude at twilight:
+	void setHorizAltitude(int);
+
 
 	//! get Show Flags from current configuration:
 	bool getShowFlags(int);
@@ -84,6 +87,10 @@
 	//! get current Sun altitude at twilight:
 	int getSunAltitude(void);
 
+	//! get current Horizon altitude:
+	int getHorizAltitude(void);
+
+
 public slots:
 //! Set whether observability will execute or not:
 	void enableObservability(bool b);
@@ -127,8 +134,9 @@
 //! @param DecSun declination of the Sun (in radians).
 //! @param RAMoon idem for the Moon.
 //! @param DecMoon idem for the Moon.
+//! @param EclLon is the module of the vector product of Heliocentric Ecliptic Coordinates of Sun and Moon (projected over the Ecliptic plane). Useful to derive the dates of Full Moon.
 //! @param getBack controls whether Earth and Moon must be returned to their original positions after computation.
-	virtual void getSunMoonCoords(StelCore* core, double JD, double &RASun, double &DecSun, double &RAMoon, double &DecMoon, bool getBack);
+	virtual void getSunMoonCoords(StelCore* core, double JD, double &RASun, double &DecSun, double &RAMoon, double &DecMoon, double &EclLon, bool getBack);
 
 
 //! computes the selected-planet coordinates at a given Julian date.
@@ -194,7 +202,7 @@
 	virtual bool CheckRise(int i);
 
 //! Some useful constants and variables(almost self-explanatory).
-	double Rad2Deg, Rad2Hr, AstroTwiAlti, UA, TFrac, JDsec, Jan1stJD, halfpi, MoonT, nextFullMoon, prevFullMoon, RefFullMoon, GMTShift, MoonPerilune;
+	double Rad2Deg, Rad2Hr, AstroTwiAlti, UA, TFrac, JDsec, Jan1stJD, halfpi, MoonT, nextFullMoon, prevFullMoon, RefFullMoon, GMTShift, MoonPerilune,RefracHoriz,HorizAlti;
 
 //! RA, Dec, observer latitude, object's elevation, and Hour Angle at horizon.
 	double selRA, selDec, mylat, mylon, alti, horizH, culmAlt, myJD;
@@ -224,7 +232,7 @@
 
 
 //! Current simulation year and number of days in the year.;
-	int currYear, nDays, iAltitude;
+	int currYear, nDays, iAltitude, iHorizAltitude;
 
 //! Useful auxiliary strings, to help checking changes in source/observer. Also to store results that must survive between iterations.
 	QString selName, bestNight, ObsRange, objname, AcroCos;

=== modified file 'plugins/Observability/src/gui/ObservabilityDialog.cpp'
--- plugins/Observability/src/gui/ObservabilityDialog.cpp	2012-09-20 12:46:16 +0000
+++ plugins/Observability/src/gui/ObservabilityDialog.cpp	2013-01-17 13:33:22 +0000
@@ -74,6 +74,7 @@
 	connect(ui->Blue, SIGNAL(sliderMoved(int)), this, SLOT(setBlue(int)));
 	connect(ui->fontSize, SIGNAL(sliderMoved(int)), this, SLOT(setSize(int)));
 	connect(ui->SunAltitude, SIGNAL(sliderMoved(int)), this, SLOT(setAltitude(int)));
+	connect(ui->HorizAltitude, SIGNAL(sliderMoved(int)), this, SLOT(setHorizon(int)));
 
 	connect(ui->closeStelWindow, SIGNAL(clicked()), this, SLOT(close()));
 	connect(ui->restoreDefaultsButton, SIGNAL(clicked()), this, SLOT(restoreDefaults()));
@@ -101,6 +102,9 @@
 
 	html += "<h3>" + q_("Explanation of some parameters") + "</h3><table width=\"90%\">";
 	html += QString("<tr><td>%1</td><td>%2</td></tr>").arg(q_("Sun altitude at twilight:")).arg(q_("Any celestial object will be considered visible when the Sun is below this altitude. The altitude at astronomical twilight ranges usually between -12 and -18 degrees. This parameter is only used for the estimate of the range of observable epochs (see below)."));
+
+	html += QString("<tr><td>%1</td><td>%2</td></tr>").arg(q_("Horizon altitude:")).arg(q_("Minimum observable altitude (due to mountains, buildings, or just a limited telescope mount)."));
+
 	html += QString("<tr><td>%1</td><td>%2</td></tr>").arg(q_("Today ephemeris:")).arg(q_("Self-explanatory. The program will show the rise, set, and culmination (transit) times. The exact times for these ephemeris are given in two ways: as time spans (referred to the current time) and as clock hours (in local time)."));
 	html += QString("<tr><td>%1</td><td>%2</td></tr>").arg(q_("Acronychal/Cosmical rise/set:")).arg(q_("The Acronychal rise (or set) of an object happens when the object rises (or sets) just when the Sun sets (or rises), respectively. The exact dates of these ephemeris depend on the Observer's location. The dates between the Acronychal set and rise are those when the altitude of the celestial object uses to be high when the Sun is well below the horizon (hence the object can be well observed). On the contrary, the Cosmical rise (or set) happens when both, the object and the Sun, rise (or set) simultaneously. It is obvious that the source is hardly observable (or not observable at all) in the dates between Cosmical set and rise."));
 	html += QString("<tr><td>%1</td><td>%2</td></tr>").arg(q_("Largest Sun separation:")).arg(q_("Happens when the angular separation between the Sun and the celestial object are maximum. In most cases, this is equivalent to say that the Equatorial longitudes of the Sun and the object differ by 180 degrees, so the Sun is in opposition to the object. When an object is at its maximum possible angular separation from the Sun (no matter if it is a planet or a star), it culminates roughly at midnight, and on the darkest possible area of the Sky at that declination. Hence, that is the 'best' night to observe a particular object."));
@@ -141,7 +145,12 @@
 	ui->fontSize->setValue(GETSTELMODULE(Observability)->getFontSize());
 	int SAlti = GETSTELMODULE(Observability)->getSunAltitude();
 	ui->SunAltitude->setValue(SAlti);
-	ui->AltiText->setText(QString("-%1 %2").arg(SAlti).arg(q_("deg.")));
+	ui->AltiText->setText(QString("%1 -%2 %3").arg(q_("Sun altitude at twilight:")).arg(SAlti).arg(q_("deg.")));
+
+	SAlti = GETSTELMODULE(Observability)->getHorizAltitude();
+	ui->HorizAltitude->setValue(SAlti);
+	ui->HorizText->setText(QString("%1 %2 %3").arg(q_("Horizon altitude:")).arg(SAlti).arg(q_("deg.")));
+
 }
 
 void ObservabilityDialog::saveSettings(void)
@@ -213,9 +222,15 @@
 
 void ObservabilityDialog::setAltitude(int Value)
 {
-	ui->AltiText->setText(QString("-%1 %2").arg(Value).arg(q_("deg.")));
+	ui->AltiText->setText(QString("%1 -%2 %3").arg(q_("Sun altitude at twilight:")).arg(Value).arg(q_("deg.")));
 	GETSTELMODULE(Observability)->setSunAltitude(Value);
 }
 
 
+void ObservabilityDialog::setHorizon(int Value)
+{
+	ui->HorizText->setText(QString("%1 %2 %3").arg(q_("Horizon altitude:")).arg(Value).arg(q_("deg.")));
+	GETSTELMODULE(Observability)->setHorizAltitude(Value);
+}
+
 

=== modified file 'plugins/Observability/src/gui/ObservabilityDialog.hpp'
--- plugins/Observability/src/gui/ObservabilityDialog.hpp	2012-08-10 15:26:42 +0000
+++ plugins/Observability/src/gui/ObservabilityDialog.hpp	2013-01-17 13:33:22 +0000
@@ -58,6 +58,7 @@
 	void setBlue(int);
 	void setSize(int);
 	void setAltitude(int);
+	void setHorizon(int);
 
 private:
         Ui_ObservabilityDialog* ui;

=== modified file 'plugins/Observability/src/gui/ObservabilityDialog.ui'
--- plugins/Observability/src/gui/ObservabilityDialog.ui	2012-08-25 13:47:58 +0000
+++ plugins/Observability/src/gui/ObservabilityDialog.ui	2013-01-17 13:33:22 +0000
@@ -6,7 +6,7 @@
    <rect>
     <x>0</x>
     <y>0</y>
-    <width>528</width>
+    <width>530</width>
     <height>556</height>
    </rect>
   </property>
@@ -351,16 +351,40 @@
             </font>
            </property>
            <property name="text">
-            <string>Sun altitude at twilight</string>
+            <string>Observing conditions</string>
            </property>
           </widget>
          </item>
          <item>
           <layout class="QHBoxLayout" name="horizontalLayout_5">
            <item>
+            <widget class="QLabel" name="HorizText">
+             <property name="text">
+              <string>Horizon altitude: 0 deg.</string>
+             </property>
+             <property name="alignment">
+              <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+             </property>
+            </widget>
+           </item>
+           <item alignment="Qt::AlignLeft">
+            <widget class="QSlider" name="HorizAltitude">
+             <property name="maximum">
+              <number>45</number>
+             </property>
+             <property name="orientation">
+              <enum>Qt::Horizontal</enum>
+             </property>
+            </widget>
+           </item>
+          </layout>
+         </item>
+         <item>
+          <layout class="QHBoxLayout" name="horizontalLayout_55">
+           <item>
             <widget class="QLabel" name="AltiText">
              <property name="text">
-              <string>0 deg.</string>
+              <string>Sun altitude at twilight: 0 deg.</string>
              </property>
              <property name="alignment">
               <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
@@ -378,6 +402,7 @@
             </widget>
            </item>
           </layout>
+
          </item>
         </layout>
        </item>