What causes this noise gradient - Atik OSC camera

[Coco]

What causes this un even gradient in the pixinsights STF tool and my OSC images? This is a stack of 5 x 5 mins @ -10 degrees auto-stretched with the STF tool? its there even in a stack of 30 images @ 5mins so I'm ruling out low signal.

I realise this is stretching at its extreme and but wondered why the noise is not equal across the full image?

Any thoughts?

[swag72]

Could it be light pollution Guy? Even when I use flats I have some gradient left in which I can only assue comes from the fact that my skies are not dark enough!

[ianaiken]

I have the same on my QHY OSC. You can see my thread about it here DBE will remove it.

[harry page]

Hi

The edge band you have comes from the CCD , make sure you use high quality bias or darks to remove these and the rest is good old light pollution gradients --- which are not that bad

Nice and smooth and easy to remove with DBE

Now this is a gradient

Regards Harry

[Coco]

Cool thanks peeps... just thought I'd check, its really nothing like this without an STF stretch..

wish I'd found the link before ... I really must use the search tool properly