Activate the driver fog workaround again. It doesn't seem to be solved yet.

simgear/scene/sky/moon.cxx

@@ -65,7 +65,7 @@ static int sgMoonOrbPostDraw( ssgEntity *e ) {
 
     // Some drivers don't properly reset glBendFunc with a
     // glPopAttrib() so we reset it to the 'default' here.
-    // glBlendFunc ( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA ) ;
+    glBlendFunc ( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA ) ;
 
     glPopAttrib();
     // cout << "pop error = " << glGetError() << endl;

simgear/scene/sky/sky.cxx

@@ -175,7 +175,7 @@ void SGSky::preDraw( float alt, float fog_exp2_density ) {
     //        certain NVidia drivers don't seem to implement
     //        glPushAttrib(FG_FOG_BIT) properly. The result is that
     //        there is not fog when looking at the sun.
-    // glFogf ( GL_FOG_DENSITY, fog_exp2_density );
+    glFogf ( GL_FOG_DENSITY, fog_exp2_density );
 
     	// if we are closer than this to a cloud layer, don't draw clouds
     static const float slop = 5.0;