wimvb

Thank you. Yes, I was pleasantly surprised.

My take on this galaxy. One of my first imaging sessions this season, and from my new home under considerably darker skies than before (Mag 20.6 vs 18.5). Gear: SW 150PDS on a SW AZ EQ6 and ASI174MM cooled cmos at 2 e/ADU. Ha: 14 x 5 minutes R: 24 x 3 minutes G: 20 x 3 minutes B: 19 x 3 minutes (Total: 4 hours and 19 minutes) Capture: Ekos/Kstars Processing: PixInsight I had a planned sequence in Ekos for exactly one hour each of Ha, R, G and B. But just before the last blue sub, Ekos decided it was time for an automated meridian flip, which it did without hickup. I decided to let it run for half an hour more, collecting Ha and R. This image is about the full fov of my camera, only the edges have been cleaned up. (click on the image to enlarge)

So, maybe in the not so distant future, in stead of having a remote setup in S France / Spain / Namibia /Chile or wherever, we will have remote space telescopes. SkyWatcher in the sky, so to speak, beyond any light pollution. The idea isn't new: https://www.skyandtelescope.com/astronomy-news/testbed-paves-way-for-amateur-space-telescope/

https://www.firstlightoptics.com/misc/zarkov-cloud-gun.html

If FLO doesn't have it, try Teleskop Service in Germany. https://www.teleskop-express.de/shop/

As @vlaiv wrote: no need for percentile clipping. Percentile clipping should only be used in case you have very few subs (less than about 10), because it's a very crude clipping method.

Here's a version with scnr only 50% strength. then DBE to remove the blue cast on the right, and a little contrast enhancement + star reduction. Remember that the image is false colour anyway. Removing the green cast but keeping the detail from the green channel, doesn't really destroy anything, it just maps it differently. The original Hubble image of the Pillar of Creation also has very little green in it. personally I like the version with less green/yellow and more reds better.

Have you tried this process (PhotoShop, but should be similar in GIMP)? http://bf-astro.com/hubblep.htm Scnr green removes the green colour cast, but doesn't alter the intensity. This means that you get rid of the green, but keep the detail/lightness from the Ha.

Here's your image with scnr green applied in PI Btw, there's a lot more to extract from the image, but the jpeg version is of too low quality to do this.

In pixinsight, I would use scnr on green, which works wonders. Unfortunately in GIMP, that luxury doesn't exist. But I believe there are colour manipulation processes that let you adjust individual colours (not just rgb, but magenta - green, cyan - red and yellow -blue). You might want to play with those.

This far in this thread, I start wondering why nobody has yet recommended the astrophotography bible. So here it is: @paul mc c: you should definitely pick up a copy of this excellent read from our sponsor FLO https://www.firstlightoptics.com/books/making-every-photon-count-steve-richards.html

Since your camera is cooled to a set point, ambient temperature shouldn't matter, as long as the cooler can keep up. That said, personnaly I would shoot darks in a cool a place as possible. There may also be other things happening; 1 how do you take darks? E.g. if you leave the camera on the scope, there's the risk of light leaks. That's why I take darks at night, with my camera covered with a lens cap and two layers of aluminium foil. 2 do you use "optimized" dark calibration? Cmos cameras such as zwo cameras, need matching darks that are used without scaling. 3 is the light edge possible residual amp glow. In that case the lighter areas should be conentrated in just a few places. It would help to diagnose the problem if you post an example.

The proper method is: Image Integration without pixel rejection for dark subs. This creates the master dark. Image integration without pixel rejection of dark flat subs. This creates a master dark flat. Image calibration of flat subs with master dark flat. The master dark flat is subtracted from the flat subs. Image integration of the calibrated flat subs to create a master flat. Image calibration of light subs with master dark and master flat. Star alignment of calibrated lights. Image integration with appropriate pixel rejection of aligned light frames. No pixelmath involved, only standard pixinsight processes.

I agree with @MarsG76 regarding the streaks. It's sometimes called walking noise. The only sure way to avoid it is to dither between exposures.

Congratulations on your first astro pic, and welcome to the dark side (& bottomless pit). 40 minutes is probably a bit much for one single exposure, but it shows what your gear can do. Ccd cameras are set to a fixed gain. The value differs between models. The gain is chosen such that the full well value (electrons) matches the largest digital number (usually 2^16 - 1 = 65535).