The preview window looks like working of one cpu core probably and take some time before it shows a changing precisely. The main render probably would do it quicker on a kind of single square plane if stripped of everything . I would like to make a test scene for that purpose and curious how to do it right. Guess I don't need the lighting, planet, atmosphere , GI, AA but still have to keep detail slider high. A kind of special tgd file for noise setting only.
I believe I can't do animation in my version but still hope to use the same idea of making a set of preview pictures.