This is my first go at imaging the veil nebula. I'm using an unmodified DSLR so the Ha signal was really low and it was quite a challenge (and a bit frustrating) to process this... still, it's an excuse to go shopping for a new astro camera, right?! The one advantage was that the full-frame sensor was big enough to capture the whole Cygnus loop in one frame.

The subs were acquired over 4 nights in August 2022 with pretty warm night time temperatures and the camera temp reading about 24 - 26 C. I think that's the processor temperature rather than the sensor temperature (not sure with a Canon 6D) but it was hot enough that there was a lot of read noise. I used an Optolong L-Extreme dual bandpass Ha and OIII filter.

Total of 171 x 240s subs

Processing Steps (Pixinsight):

Pre-processing: Calibration and debayered to separate R,G, and B channels. Aligned and drizzle integrated with local normalisation.
Background: Dynamic Crop and DBE to take out the borders and even out the background
Linear Noise Reduction: TGV denoise followed by MMT - method from Jon Rista (https://jonrista.com/the-astrophotographers-guide/pixinsights/effective-noise-reduction-part-1/ ).

Luminance Image:
- RGB channel combination, Extraction of luminance (colour image discarded), Deconvolution - method from Jon Rista (https://jonrista.com/the-astrophotographers-guide/pixinsights/proper-use-of-regularized-richardson-lucy-deconvolution/ )
- Very slight stretch till the nebulosity is just visible and then Starnet ++ (with star mask) to get starless luminance image and stars image
- Further stretch of starless lum image using Generalised Hyperbolic Stretch ( https://ghsastro.co.uk/ ) - brilliant script!
- Local Histogram Equalisation
- MMT sharpening
- ACDNR for noise reduction
- PixelMath to add the star image back

Chrominance Image:
- PixelMath to create synthetic Ha image (0.9 * R + 0.1* B) and synthetic OIII image (0.6 * G + 0.4 * B) - no deconvolution used
- Slight stretch of Ha and OIII images followed by Starnet ++ to get starless images and star images
- Further stretch with Generalised Hyperbolic Stretch ( https://ghsastro.co.uk/ )
- PixelMath to create colour image - dynamic combination as per https://thecoldestnights.com/2020/06/pixinsight-dynamic-narrowband-combinations-with-pixelmath/
- Curves Transformation to tweak saturation, hue etc.
- ACDNR for noise reduction
- PixelMath to add stars back
- Convolution to blur image

LRGB image:
- LRGB combination
- Export as TIFF
- Photoshop for final crop, minor tweaks and export to JPEG