Robert,
I'll take off my astrophotography hat and replace it with my science hat to try to make sense of the image by going through the literature you have supplied.
Now that the atmospheric UV background has been identified as causing potential havoc I've been able to further improve the synthetic luminance image that filters out most of the older population of stars and emphasises the blue stars in the image.
The role of the UV background can be seen in comparative sum and average stacked images using AIPWinV2 in the attachment.
The attached image is a screenshot, no adjustments to the histograms have been made.
The filtered image can be found here.
http://members.iinet.net.au/~sjastro/CentUV_B.jpg
Details.
10 hr near UV exposure average stacked.
A synthetic L image L=B + 30*UV was produced. B= 0.8 hrs total.
(B+30*UV) L, 0.8 hrs R, 0.8 hrs G, 10 hrs UV
BRC-250, ST-X10ME.
Clear skies
Steven