Dust + Stars + Nebula

Okay, so here's the first attempt at combining all 3 layers together.  Some obvious issues with balancing the 3 to get it to look right. 

Stars- maybe just need a whole bunch more... they seem to be overwhelmed by the darker dust/nebula particles.

Dust- Current alpha may include too much of the faint dust areas, creating a bit of a pileup in areas.  May need to tweak original alpha and recull to get a more spidery feel.  Also, a fractal noise added to the density or alpha of the dust in the vertical direction may help the spidery/tendrilly feel in the original Hubble image, particularly when viewed from the side.

Nebula- Doesn't integrate as nicely as I would like.  Too dark around edges?  Also no real hotspots in center where star formation is taking place.  This was removed in the original texture map, but it may need to be added back in.  Also, nebulae don't naturally extend throughout the height of the galaxy, they're usually about as deep as they are wide, so fixing that should probably be on the list too.

Total: 6,647,621

Stars: 4,781,374
exposure: 0.02
radius: 0.05

Dust: 1,468,095
exposure: 0.005
radius: 0.05 - 0.15

Nebula: 398,151
exposure: 0.005
radius: 0.05 - 0.15