Original Post
Hi, Lesson 44 is the lens flare tutorial. Apparently, it has occlusion testing. If the situation is right, it can be done vastly more efficiently. In Python:I used this technique to produce: 
The planet can occlude the sun's flare. It does so perfectly. Hope this helps, Geometrian
model = glGetDoublev(GL_MODELVIEW_MATRIX)
proj = glGetDoublev(GL_PROJECTION_MATRIX)
view = glGetIntegerv(GL_VIEWPORT)
winx,winy,winz = gluProject(lightpos[0],lightpos[1],lightpos[2],model,proj,view)
winz = glReadPixels(winx,winy,1,1,GL_DEPTH_COMPONENT,GL_FLOAT)
pos = gluUnProject(winx,winy,winz,model,proj,view)
#if pos and lightpos are basically the same and 0<winx<view[2] and
#0<winy<view[3], then the light is visible; draw the flare.