Per #2966, add new solar_time() function to the vx_solar library.

dtcenter · Nov 4, 2024 · 2c13fda · 2c13fda
1 parent 5784b8a
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diff --git a/src/libcode/vx_solar/solar.cc b/src/libcode/vx_solar/solar.cc
@@ -60,6 +60,49 @@ return;
 ////////////////////////////////////////////////////////////////////////
 
 
+double solar_time(unixtime gmt, double lon)
+
+{
+
+   //
+   //  right ascension and declination
+   //
+
+double Ra;
+double Dec;
+
+solar_radec(gmt, Ra, Dec);
+
+   //
+   //  local hour angle
+   //
+
+double lha = gmt_to_gmst(gmt) - lon - Ra;
+
+   //
+   //  rescale angle to -180 to 180
+   //
+
+lha -= 360.0*floor((lha + 180.0)/360.0);
+
+   //
+   //  rescale local hour angle to decimal hours of the solar day
+   //
+
+double solar_hr = (lha + 180.0)/360.0 * 24; 
+
+   //
+   //  done
+   //
+
+return solar_hr;
+
+}
+
+
+////////////////////////////////////////////////////////////////////////
+
+
 void dh_to_aa(double lat, double Dec, double lha, double & alt, double & azi)
 
 {

diff --git a/src/libcode/vx_solar/solar.h b/src/libcode/vx_solar/solar.h
@@ -46,6 +46,25 @@ extern void solar_altaz(unixtime gmt, double lat, double lon, double & alt, doub
 ////////////////////////////////////////////////////////////////////////
 
 
+extern double solar_time(unixtime gmt, double lon);
+
+   //
+   //  calculates the solar time for the given longitude.
+   //
+   //
+   //  Input:   gmt, greenwich mean time expressed as unix time
+   //
+   //           lon, longitude (degrees) of given location (+ west, - east)
+   //
+   //
+   //  Output:  decimal hours f the solar day in range [0, 24),
+   //           where 12 is solar noon
+   //
+
+
+////////////////////////////////////////////////////////////////////////
+
+
 extern void solar_radec(unixtime gmt, double & Ra, double & Dec);
 
    //