Image:
Image with Chandra X-ray:
Details & Credits:
:You can find all the details of acquisition and research done in the astrobin post here: https://www.astrobin.com/ug8i0t/
You can find a zoomable version of both images here: https://elveteek.ch/en/casa-dsc/OSH
Processing:
This was an especially tough image to work with because of the density of the starfield. Most images like this can be dealt with using tools such as starnet or multiscale techniques to separate stars from everything else. However, because the filamenary globs of gas from the snr looked too much like stars, I had to instead stretch the image creatively actually show off the nebula.
Background Flattening:
Multi-scale Gradient Removal was used to remove any widefield gradients from the Ha, Sii, and Oiii stacks.
Noise Reduction
Noise reduction was done in similar fashion to the method outlined by Charles Hagen. https://www.nightphotons.com/guides/single-channel-denoise. Two significant changes to this method were made. First, in order to stop DeepSNR from creating small scale stars out of noise, a slight TGV noise reduction was applied. Second, instead of blending noise back into the image linearly, noise was added with the square root of intensity, allowing a more “natural” distribution.
Other linear processing
These steps were used to finalize the monochrome channels before combining them into the final image
- Deconvolution on each channel’s nebulosity using the Regularized Van-Cittart algoritm
- BlurX only targeting stars to shrink the stars
Non-Linear processing
In order to combat the trials of color balancing, I stretched each color channel individually, then combined.. ArcsinH stretch was used to stretch in order to damped the starfield.
The colors were then balanced using CurvesTransformation and HT
The image was then stretched more using HT. Red intensities were increased using exponential transform, and blue regions were intensified using a B-R+med(R) mask.
Stars were reduced, and the overall image was stretched slightly more.
Blue intensities were increased using a B-R mask and curves
The overall image was then darkened slightly using HT to preserve contrast, as the image could not support the brighter form
The X-Ray observations were added using histogram compression.
One thought on “A 525 hour Cas A collab – Processing notes”
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