Astronomical ObjectsThis image contains several Sharpless objects:
- SH2-156 aka IC 1470 The tiny nebula on the right
- SH2-157 aka The Lobster Claw Nebula
- SH2-158 aka NGC 7538 aka Northern Lagoon Nebula aka Brain Nebula - Dreyers Object
- SH2-161 The big diffuse structure at the bottom
- SH2-162 aka NGC 7635 aka The Bubble Nebula
- SH2-163 The Smaller Nebula on the left
There are also two beautiful open star clusters
- M52 aka NGC 7654 aka The Salt and Pepper Cluster
- NGC 7510 aka The Dormouse Cluster aka The Arrowhead Cluster
Processing in Siril:The three channels H, S, O were combined with pixelmath to a color image as follows:
R: 0.6*S + 0.4*H
G: 0.7*H + 0.3*O
O: 0.7*O + 0.3*H
I found that more complicated formula didn't help much for the colors.
After that the following steps were also done in Siril:
- Histogram Calibration
- Background Subtraction and Background Color Calibration
- GHS for all channels with stretch factor 1 and local stretch intensity 1
- additional GHS for the blue channel only with stretch factor 1 and local stretch intensity 1 again
Postprocessing in Rawtherapee:- Increased Blackness of the Background
- Highlight Protection to bring out the very bright parts of the nebula better
- Noise Reduction as well as Detail Recovery
- A small enhancement of the color saturation
More could have been done with star subtraction, but unfortunately starnet++ refused to do the job this time
Bright Halpha-emitting region with the Bubble NebulaDuring Processing I found that there is a very bright Halpha emitting object within the Bubble Nebula. It is about ten times brighter then the next brightest Halpha emission in this picture. Its easily mistaken for a line of stars, but unlike stars it almost only emits in Halpha, emission in SII and OIII is weak. With histogram transformation it is overexposed already. It looks a bit like a jet. I include a B/W Halpha images of the object with linear scale. Later I found that the Bubble Nebula has also been photographed with the Hubble Space Telescope. It is an extremely beautiful image and it shows that the structure is not a classical jet:
https://hubblesite.org/contents/media/images/2016/13/3725-Image.html 
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