I'm pretty happy with it now. It is composed of 4 main layers, similar to the one i posted in my previous post. I still have to fit in some dark clouds and to make the parameters dependant on an input table, but the code is pretty much done.
The next step is to create a separate thread to calculate the textures, to use a disk cache (to avoid regenerating them every time), and maybe to add a kind of additional glow/lens effect to the very bright stars.