Try this:
1. Un-tick the "Render surface" tick box in the Planet node.
2. Place the camera at position 0,0,0, angle 90,0,0.
3. Add a "Low level Cumulus", set its thickness to 2000 and its height to 1000. This will place the start of the cloud just above the camera which is pointing straight up.
4. Go to the Clouds Density fractal and change its Fractal type to Perlin Ridges and lower its coverage to about 0.25. You will probably want to change the scale and lead in scale possibly dropping them by a factor of 10 or so.
5. Go back to the cloud layer and choose a good nebulus colour, say dark red
6. Repeat from stage 3 using different seed values, scale and colour.
Set your cloud densities quite low, say 0.005 and your edge sharpness to 0.5 together with high quality settings and Acceleration Cache set to "none (highest detail).
That should work for a bunch of situations.
Seemed like an interesting idea so I'm rendering an attempt now, I'll post an image and tgd in a bit.
Hmm, I think this'll need quite a bit of work but you can see the principle here. If anyone has another suggestions please chime in
Richard
