sun: halve disc size and add brightness gain

config.js

@@ -649,7 +649,10 @@ window.CONFIG = {
     // drawn larger so it reads as a disc; the surface brightness and the
     // scene lighting are NOT scaled with it.
     sun: {
-        angularRadius: 0.0558     // 12x the physical 0.00465 rad
+        angularRadius: 0.0279,    // 6x the physical 0.00465 rad
+        brightness: 1.8           // sun disc/halo gain
+        // angularRadius: 0.0558, brightness: 1.0
+        // angularRadius: 0.0140, brightness: 2.4
     },
 
     // ------------------------------------------------------------------