Hmm. What effect you want to have exactly?
After reading the posts I'm somewhat confused about everything except the sphere's internal attributes.

The internal attributes, or the atmosphere, are not existant because the sphere is empty for the renderengine. If you make a massive sphere you have of course material attributes at any point inside the sphere as well as on its surface.It should then be transparent on the inside so that you will see something...
Some atmosphere that comes close to the one you posted in your first msg. would have these attributes:
Light wavelength [R,G,B] = 4e-07, 4.25e-07, 6.15e-07
Star Irradiance [R, G, B] = 1350 1250 1400
Transparency treshold = 0.94
Modifier = 0.97 (for an 150km high atmosphere)
Modifier = 0.8 (for an ~ 3km high atmosphere)
AO modifier = 2.7           
Twilight width = 0.005 (for r = 17000 km)
Incidence at horizon = 0.165
Out of some meteorological computing...
now, if you want the blue to be less intense or dark, you would adjust it slightly with color math and primarily via the irradiance, transparency treshold and it's modifier.
BB got it somehow right in the description, I think, and that means that you have to cheat a little since you can not input meteorological data 1 to 1. Rape one of the nodes and use poser math to limit the effects.
The artifact that looks like a object which isn't in your scene should be gone after filtering the results. A colorrramp can do some good here. And of course all the +, -, *, mod and clamp stuff.
I can not rebuild the scene like described in post #2 because I fail to see any 2nd dome there or where it was placed. I only see one sky dome ball prop and one small ball prop there.