David it is most probably a combination of light pollution, gradients and the fact that a DSLR has twice as many green pixels as that of red or blue. Faint stars first show in the green signal as pseudo noise. This region is still quite low and only at about fifty degrees above the horizon at morning twilight start. I will get much better data when I can collect through the zenith.
I managed to get another set of data after the Moon set and before twilight this morning to make a rough mosaic. Same collection parameters as before except the fridge was at -10C. The improvement is obvious.
Medium image here 6MB
http://d1355990.i49.quadrahosting.co...2/rho_mos1.jpg
Without the new fridge I would never get the faint dust with so little noise. It can only get better when this region is higher.
Bert