#Atmosphere
Jeff,
you could use an opacity map. Create it with animator pro, or a similar paint
package, using a grayscale pallette and rgrad (radial gradient) ink. It would
be need to be a solid white circle on a black background with a gradient of
white to black around the outer edge. You could map this planar to the
atmosphere sphere object. It may only work if you stay at the same camera angle
to the atmosphere. If you go around the planet you might have a problem and I
can't think of a solution for that other than post-processing a haze in video
post, or similar technique.