THE CYGNUS LOOP
Veil Nebula • Supernova remnant • Cygnus • 2400 light-years from Earth
🔭
Askar FRA400
📷
ZWO 2600MC Pro
🌃
Bortle 8
⏱️
15 hours
🗓️
Aug & Sep 2021
Overview
The Cygnus Loop is a vast supernova remnant formed by the explosion of a massive star around 15,000 years ago. Located roughly 2,400 light years from Earth in the constellation Cygnus, it spans several degrees of sky and consists of delicate filaments of glowing gas expanding outward into space. These intricate shock fronts make the Cygnus Loop a striking and scientifically rich target for astrophotography, particularly for One Shot Colour camera using dualband filters.
Background
This was a tough image to edit, and I ended up restarting from scratch three times until I settled on something I was happy with.
The supernova remnant has a lot of green data in the integrated image — both within the structure of the gas that I wanted to look prominent, and also the background noise that I didn’t. Initially I tried keeping the remnant’s green in while removing the noise, but couldn’t get it looking good. Eventually I gave up and went with the nuclear option (PixInsght’s SCNR function to remove all the green). This smoothed out the background, and flipped the green in the gas to be more blue — which, happily, I like the look of.
I also had a tough time evening out the background. I tried a lot of different things, including loading the image in Photoshop and using Gradient eXterminator. Eventually I found that PixInsight’s AutomaticBackgroundExtractor (ABE) with the function degree setting set to three did a good job.
The framing was very tight around the entire Cygnus Loop, so I cheekily did a bit of Photoshop work to expand the canvas size and clone in more stars. This gives more “breathing space” around the edges of the photo. If I ever get a reducer for my telescope, I could have another go with a lower focal length and so avoid the need for that bit of cheating. I think the image would also benefit from a longer integration time (this is 15 hours) but the weather forecast is terrible and I want to wrap this one up!
When editing, I couldn’t help but notice that part of the Loop looks like a xenomorph head. See what I mean?
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Kit list
This is the equipment I used to capture the image.
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Telescope: Askar FRA400
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Camera: ZWO ASI 2600MC Pro
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Guidescope: William Optics 32mm Slide-Base Uniguide
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Guidecam: ZWO ASI 120MM Mini
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Control: ASIAIR Plus
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Filter: Optolong L-eXtreme
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Example source data
Here’s an example single subframe and freshly integrated stack, just with simple stretches applied.
Seestar S50 image
This photo showing part of the Cygnus Loop was taken using my Seestar S50 telescope.
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Definitely a xenomorph head!
I know, right! Now you’ll never be able to see it as anything else 🙂
I am editing my image of the Cygnus loop taken with a Samyang 135 and a ASI533MC Pro with a L-extreme. I feel for your editing pain. I had the same issues and used SCNR for the same reasons. I also used GraxPert to get rid of the unneeded red background. My challenge is integration time. Mine only has 70 subs = ~ 2 hours. Will add much more and see if I can bring up the fine detail between Pickering’s Triangle and the Eastern Veil.
Good luck, it’s a surprisingly tough target!