Attached Link: http://www.zurg.net/dan/posertemp/starfield1.mt5

Ok, I'm making some progress here. I've replaced the source texture with a spot texture and a fractal sum texture and this is what I got. Unfortunately, the "rightness" of this look seems to vary with resolution, so I may have to find a way to factor that into the parameters.

I'll post more when I've got it figured out. The current shader here is posted as
http://www.zurg.net/dan/posertemp/starfield1.mt5
http://www.zurg.net/dan/posertemp/starfield1.png