[avandonk]

Sorry Mike I should have said they were all taken with the Canon 5DH and the Canon 300mm lens. The field of view in all is near 6.8x4.5 degrees.
A 200mm lens would get the equivalent FOV with a C size sensor (24x15mm).

I am starting to think that the blue cast is due to light pollution and if I eradicate it I lose any faint blue nebula. If you notice
the blue nebula on M20 it is all there. Thats why I have started dabbling with narrowband imaging. The solution to this is dark skies and unfortunately we cant all live in the outback. We are still more fortunate than our North American, European or Asian brothers as we have nowhere near their light pollution or air pollution.

Fast apertures f/2.8 will very quickly show any gradients no matter what the source. I had a set of exposures with very strange coloured gradients and I figured out it was due to fireworks from the opening of a nearby (1k away) Bunnings store!

When I do long say 15min exposures I try to do this with the target object as near to the zenith as possible.

Bert