M51, LRGBHa, is there anything that can be done with this?

[iapa]

I had some data from a couple of years ago from an ASI1600MM-C, with LRGBHa filters on a Quattro 10"CF

There is a lot of gradient that I can't seem to get rid of using PixInsight (I am new to this app as well).

• 200 x 60s Lights
• 140 x 60s Blue
• 139 x 60s Green
• 138 x 60s Red
• 139 x 60s Ha

Image05.fit

LRGBHa were preprocessed using WBPP 2.4.3

I then used

• LRGB Combination ( ignoring Lum) and 
• DBE, 8 pixels, 50 per row, subtraction and division, separately
• ABE on each of those
• BGneutralisation

no joy

[ONIKKINEN]

Did you calibrate the data?

There is overcorrection of flats and also dustspots still visible so flats have not worked at all. The colourchannels also have different vignetting, so maybe different collimations? That would mean each filter must have had their own flats after each session, or its a no-go in terms of flats calibration. As a newtonian imager this all looks very familiar if i didn't take flats during each night. The blue channel has dark halos around stars (no idea whats the problem with this, but also i dont know how to deal with H-alpha containing data so if its something to do with that i cant say yay or nay)

The data is quite deepfried like this and ideally you would calibrate and then stack again but if its an old dataset then maybe not possible?

You can try to bruteforce the background to be workable with: https://www.graxpert.com/ . I tried it and while it still needs some work to even out the background it probably will turn out to be an image if you work on it. GraXpert is the best tool i have used when it comes to flawed flats and deepfried backgrounds, really works wonders so give it a try (its free!).

GraXpert background removal:

Stars have odd colours when M51 looks ok to me (i did simple Siril colour calibration). H-alpha thing? Try to run GraXpert on each of the stacks before the RGB combination thing and see if you get a better image.