"Haunted" Photo -- Ghostbusting Needed

[JohnSadlerAstro]

Hi,

Is this weird effect caused by cloud or haze? I've used flats to remove genuine gradient, but there are whole patches that are lighter than the rest of the background. Humidity was high (85-90%) and visibility was down to Moderate (5 mi). Can anybody bust this ghost? (last photo had an almost perfect background, I could remove the residue of gradient, and it looked NOTHING like this)

John

[wxsatuser]

Flats are for optical train not gradients.

[JohnSadlerAstro]

Hi,

Pardon my ignorance, but isn't Gradient caused by deficiencies in the optical train? Like vigneting?

John

[wxsatuser]

Gradients can be from a few sources but they are external to the optical train.

LP and airglow are two things that produce gradients.

[JohnSadlerAstro]

Ok, thanks for correcting me on that.  Do you think that the uneven background could be caused by cloud passing across the view?

John

[wxsatuser]

Yes.
I found that thin cloud or contrails could do that.
I quite often had slow contrails do it, ruin several subs then the next ones are ok.

Tony Hallas did show dithering could remove the effects of thick smoke, may be it will work on thin cloud as well.

Pixinsight's DBE is superb at removing gradients btw.

[JohnSadlerAstro]

Hi,

Looking through my subs, I can see that in the last 60%, there is significant gradient caused by clouds (is that right?) making the top appear more exposed than the bottom. I'm trying a restack with some additional data taken last month.

John

[glowingturnip]

it's not amp glow is it ?  do the darks have the same pattern ?  I had a Nikon D80 with horrid amp glow, but would have thought your Canon would be ok

[JohnSadlerAstro]

Hi,

No, I'm pretty sure it isn't; my camera has never suffered from that. Unfortunately, we're in a really damp (i.e. 90-95% humidity) whether system at the moment, so I think I may as well forget astronomy until that goes away.

John