M42 gradient problem

[mynameiscd]

Here's one from last friday night.
Had a problem with my flats i took on saturday morning.
I didn't have a good look when i took them so after a few days i had a look and theres an obvious gradient problem.
The pink is usual like all the raw images because of the camera mod but there is a definite gradient from top to bottom.
Is there a way to fix up the flats before i stack them or can i do it post processing in photoshop or just leave them out this time and make sure i get the tshirt right and point the scope away from the morning sun sidelight.
I dont have gradient xterminator yet but most of the things i read about it seem good.
I also took a few more that night and with the flats they look like i live near a city or the moon is rising.
A rough pole align with by eye through the spotter scope.
Lucky its dark here and you can spot sigma octanis with naked eye so with the spotter i can set the cross hairs to the pole by eye and im getting 2 mins with only a little trailing.

M42 image
No guiding
40x2min lights
Darks, bias, and flats applied
Stacked in DSS
Processed in Photoshop.

[Gavin1234]

Beautiful image mate, very natural colouring. Do you separate your image train in between shoots? If you don’t then I would just take the flats another day.

[mynameiscd]

Thanks Gavin,
Yeah I normally cover with a tarp and then do flats in the morning then strip it all down.
Maybe ill keep the camera conected and try the tablet screen method.
One day ill get a light box and make it easier and also an observatory so I dont have to strip down each time.
Cheers
Andy

[Gavin1234]

Yeah I keep my camera connected if I have to move my scope and I’ve put little marks on all the movable parts to make sure it all stays aligned.

I use a white screen on my iPad over a T-shirt for flats. I used to do new calibration frames every night but now I do them every few weeks and I haven’t noticed any difference, they seem to work just as well.