M45 - The Pleiades

ahh, so you're really pushing the levels here to get the horsehead, thus increasing the noise in the image.

But, are you saying that less light = more dark current on the chip, I cant see how this can be or how this explains this shape as the intrinsic 300D red noise pattern is very different to whats in the image, but, I'll take your word on the 1.25 inch setup is somehow causing this artifact.

What was really pushed was the histo medium level was pushed back about 1/3 towards the black point. This was to lighten the nebulosity really, and as Dave G says, we pushed the medium until the port hole effect that the 1.25" adapter creates became nearly visable.

Dave G is currently looking to buy a 2" adapter which will give the same field illumination as you would find in one of my ZS80 shots.

Having played with the M45 image, we reprocessed my ZS80 M45 and found that basically the same amount of nebulosity is available as well, which really calls into question exposure lengths vs detail. But that is another thread I think!

I can post a stretched version to show the port hole effect if you like?

Later,

Jed.

Dave/Jed.
Thats very interesting guys, you can see some minor vignetting on the edges of that shot, just as you might expect. A pity that the 1.25 adapter causes so much trouble. Was the background fairly dark before the software reddened it up?
I understand what you're saying Jed regarding the histo level,
The image does credit to the both of you lads, lets hope we get more clear skies and images this winter.

I'll hopefully will be getting a decent set of H filters sometime this year, I presume that these filters are really for photographic use?