Finally, after several months of sleepless nights I managed to create semi-automated process to color balance and match DSS plates into more-less solid mosaic (I'm working on DSS2 all sky survey for the SKY-MAP.ORG project)

I processed all sky at 1/16 of full resolution and half way processing at full resolution.

Meanwhile I have a question for astrophoto gurus:

I'm pretty much happy with most of the areas, nebulae, i.e. Lace-work nebula - http://server3.sky-map.org/?img_bord...mg_source=DSS2
Flame nebula - http://server3.sky-map.org/?img_bord...mg_source=DSS2
dark nebula above Antares - http://server3.sky-map.org/?img_bord...mg_source=DSS2

But most of galaxies look too bluish
Andromeda is more-less ok to me - http://server3.sky-map.org/?img_bord...mg_source=DSS2
But other galaxies...
i.e. http://server3.sky-map.org/?img_bord...mg_source=DSS2
http://server3.sky-map.org/?img_bord...mg_source=DSS2

The question is how too adjust my process to fix galaxies, but leave good areas unchanged or changed insignificantly. It could be some simple change in color calibration function. I can spend another month to figure it out, but for you it might be something obvious.

There are still few significant edge plate problems in the mosaic, but I have some solutions to solve it. But if you zoom out you'll notice quite spotty background. I'm still looking for a way to solve it. Any ideas?

Thanks,
Sergei