[pjphilli (Peter)]

Hi

I have a Qhy8 camera which I use for deep sky imaging in a NW suburb (Thornleigh) of Sydney. As usual sky visibility is pretty poor even on the best of occasions and not helped by a nearby major road with sodium lamp lighting. I use a neodymium light pollution filter.

I notice that imaging of feint blue (reflection?)nebulosity is consistently worse than feint red (emission?) nebulosity. Last Sunday night I imaged
the Running Man nebula which has a large proportion of blue nebulosity.
I notice that I could only capture the more dense blue nebulosity.
Although the sky was clear of clouds there was a NE sea breeze blowing
and the dew was pretty fierce (not uncommon from this wind which
blows from the sea).

I would like some comments on this phenomenon. Maybe the very moist
atmosphere absorbs the shorter blue light more than the longer wavelenth
red light?

Cheers Peter