Hm ok, so the planet in the preview makes 1 rotation in exactly 50 seconds. Assuming you have a 60 Hz monitor that would make for 3000 frames, which is a lot. If you want it like the preview I recommend you use the shaders themselves directly instead of an image.
If you really want an image you could try a gif with 1000 frames and a length of 17 seconds. Or a spritesheet of say 50 frames wide & 60 frames high. Both of these will take some time to export however.
Hope that works!