Are you doing any form of noise reduction on this? also, are you using dark frames?
There does appear to be fairly strong noise in the background (which is quite normal for the dark background of an image) which either a set of dark frames, or some good quality noise reduction in post processing should make pretty easy work of!
Yes I use darks but no attempt at noise reduction. I admit that a lot of my shots appear to carry a far amount of background noise that I attempt too hide in Photoshop by adjusting the blacks. Maybe this is not that effective?
Yeah, raising the blackpoint is a common way that people try to hide background noise, however that will regularly result in loss of important data, and an unnaturally dark background.. Strangely enough, it is not regarded as 'correct' for the void of space to be rendered as black, but rather, a dark neutral grey...
A couple of tips.
1 - It is commonly considered to be best practice to expend the largest portion of your exposure time on Luminance data. between 2 and 3 to 1 is the common ratios people aim for. So say, 3h L, 1h R, 1h G, 1h B. or 4h L, 2h R, 2h G, 2h B.
Luminance is where your image will get all its detail, but also where you want to focus your effort getting the cleanest image possible. Your colour data can in fact, be quite noisy, and you can be quite agressive on noise reduction with colour data (even convolving the colour data to essentially blur noise out of it).
Think of the Lum as a 0.05mm fine line pen, and R G B as crayons essentially..
2 - Noise reduction is almost always required at some extent. I've got images from my bortle 5 backyard with over 35h of integration in 600s subs, and there is still noise that needs to be removed from the data...
3 - You don't have to travel too far to get to considerably darker skies... I sometimes complain about my Bortle 5 backyard, wishing I was still at my old place in Bortle 3/4, however, I'm less than 50km from Brisbane CBD.. From my memory, Blackburn is about 20k east of Melbourne CBD.. Somewhere like Healsville, Kinglake or Yarra Junction would get you out to Bortle 4~4.5, and that will make a CONSIDERABLE difference.
I know where I'm living right now is 11km from my old house, and my old house was right on the edge of Bortle 4/Bortle 3, but my current location is SOLIDLY bortle 5.
The difference between Bortle 5 and Bortle 4 is vast. So your Bortle 6/7 location in Blackburn to the Bortle 3 in Warburton would be outstanding.
You could probably get similar results with 50% the integration time.
