Nice image.
The dust is fairly faint. Perhaps 15minute exposures may have been the go.
Getting the dust to show up above the background is a trick.
Perhaps also the data is there and it could be extracted more with careful curves and shadows/highlights and even the sponge tool set to burn.
This one I took was with an FSQ106 at F5 with an STL11000CM one shot colour. It was several hours though and 15mins subs. About 4 or 5 hours total from memory:
http://www.pbase.com/gregbradley/image/66960066
Getting the dust to stand out was the processing target and smoothing the noise when I did.
Greg.