Editing tutorial - Further post editing of NGC 7000 The North American Nebula

 A few nights ago I managed to image NGC 7000 The North American Nebula and I was very pleased with the results. This post documents the night and my first image. 

https://undersouthwestskies.blogspot.com/2025/06/imaging-ngc-7000-and-ic-5070-using.html

A day or two later and I have had another go at post editing and this is the resultant image. 

And here below is the original 'first effort' post editing of the data from a few days ago. 

Quite a difference isn't it. I have managed to regain some of the nebula detail particularly in the areas I'd originally blown out. I think there is better definition an structure to some of the key features as well. 

On the negative side - the colour balance still isn't right is it? I think it should be a deeper red colour but maybe I'm wrong on that?  

Anyway, in the spirit of being a lifelong learner, please give me some feedback. It will help me and other beginners who visit these pages. All constructive criticism is welcome in the comment box at the end of the post and thanks for taking the time to give me and others useful feedback. Appreciated. 

So what were the editing programs I used second time around? 

• SIRIL V1.2.6
• Affinity Photo
• Photoscape X

I followed the following video I found on YouTube - 

How did I change my normal post editing workflow this time round? 

You can read about my normal post editing workflow in a past post - here: https://undersouthwestskies.blogspot.com/2025/01/a-beginners-guide-to-using-siril-some.html

This time around there were a few changes to what I do: 

• I didn't use GraXpert
• No deconvolution (not sure about this one - but I religiously followed the video) 
• Workflow was all done in SIRIL as follows: 
• Crop and rotation
• Background extraction - and playing around with parameters more; did it twice
• right hand mouse click and 'aberrations' to take a close look at the stars 
• Colour calibration to get background neutralisation and also accurate 'whites'
• Photometric colour calibration - ensuring focal length was more accurate - reflecting that I was using 135mm lens on APS-C crop sensor DSLR
• General Hyperbolic stretch - using modified arcsinh in linear mode. I had drawn a tiny square on an area of dark background sky (when zoomed into the image). Used eye dropper to set symmetry point and then moved the middle and right hand side slider triangles about; also applied some highlights protection as well.  Repeated GHS x 3
• Colour saturation adjustments - repeated for just cyan-blue adjustment as well 
• Cosmetic correction applied
• Starnet applied but with 'pre-stretch' box unticked
• On starless image in linear mode - Histogram transformation  - just red channel - a few subtle repeat adjustments
• then HTF on all colours
• Colour saturation adjustments 
• another GHS on 'even weighted luminance' mode
• Close starless image and open starmask image
• Green noise reduction 
• Colour saturation adjustments - reduced slightly; repeated, reducing pink-red colouration slightly
• Histogram Transformation - reducing stars by moving middle and right hand slider triangles
• close starmask and re-open starless image
• complete background extraction on this image - ensure no red squares are on nebulosity areas; increase samples line slider; add dither - switch between compute background image and 'original' image to see changes
• Histogram transformation - adjust red and repeat - small iterations
• Star recomposition  - GHS - select black point in menu - make small adjustments 
• recrop to preference
• GHS - on all colours - use symmetry point based on square in area of dark background within nebula area
• colour saturation adjustments - first on global; then repeat for  pink-red and then again for cyan-blue
• Histogram Transformation minor adjustments
• SAVE as TIFF and open Affinity Photo 

In Affinity Photo: 

• in Camera RAW 'develop' persona - adjustments to basic elements (exposure, white balance, saturation, vibrance, contrast, brightness etc
• back to camera editor - denoising, sharpening, level adjustments 
• EXPORT as PNG

In Photoscape X

• Film - find overlay that best adjusts final image and apply
• Insert text and logos
• SAVE as PNG

I learned much more about how to do GHS and use color saturation from the above video.  I will try doing this again but next time including GraXpert and also Deconvolution in SIRIL