My first idea was to point you to EVE-Online. They have a real beautiful sun-rendering. I try to add this to Libertine, too. But I think that it is not so very easy to copy because you have to know in each timeframe if the sun is behind or close to an object. Therefor you need to render each triangle separately to access its position (not so very easy to figure out, if you use display lists like me). If you are able to know your objects in between you can use gluUnproject/gluProject to receive the z distances and size the texture of the sun flare in relation to the distance to the object in between.

I always try to understand why everyone uses Quaternions in game-development. As far as I know the main advantage of quaternions is that you don't have problems with quadrants and large angles (instead of small angles used in linearisation problems). Is that the fact or are there other advantages? I'm pleased with OGL transformations. They do all I need. glTranslate moves from one point to another, glRotate... well... rotates and glMultMatrix multiplies the projection matrix with my self made transformations. One hint from my side: try to avoid using angles - use vectors. Better rotate to local coordinate systems (cross product of two unit vectors result in a 3x3 transformation matrix capable of rotating your vectors to local coordinate systmes). Angles should be a result not an input. Anyway, I understand that you use Newton for space dynamics - so you have to use at least a 6x1 accelration vector for your ODE's. Newton gives you the answer to your accelration input - in my oppinion you dont need angles. But teach me if I'm wrong.