Capturing the Cygnus Wall

Located in the North America Nebula, the Cygnus Wall is so distinctive that it has its own name, and with good reason. It spans about 20 light years and exhibits the most intense star formation in the nebula. To put that into perspective, it would take us around 18,000 years for our fastest probes to reach Alpha Centauri, our closest neighbour. Simple maths tells us that to cross the Cygnus Wall would take 81,720 years JUST to travel its length. And that’s not even the largest deep space object.

An area of intense study, it is easily visible in any long exposures of the area, and with the advent of DSLRs and dedicated astronomy cameras, it’s a subject of great interest, both in broadband and narrowband imaging. It is rich in both hydrogen alpha and oxygen, and these both show up well in images captured with dual narrowband filters. The more traditional Hubble palette of sulphur, hydrogen and oxygen, is what I planned to do with this one. But, when you’re using a dual narrowband filter, and you only capture the hydrogen and oxygen, how do you incorporate the sulphur?

Cygnus Wall captured in 1910. Credit unknown

Processing

Usually I’d extract the hydrogen and oxygen channels as well as an RGB version and then paste the two into the red, green and blue channels to produce a HOO (hydrogen for red, oxygen for blue and green) palette, and then mess about with them in Photoshop.

But, if you’re trying to recreate an SHO (sulphur, hydrogen, oxygen) image, you have to go about it another way. As well as extracting the hydrogen and oxygen channels, you also need to extract a mono image, and it’s this that you’ll use as the fake sulphur channel. I’ve tried this before and in all honesty it didn’t go well.

This time out I stumbled across a You Tube video from Astro With Eric, and he talks us through the first part of that and then recombining them in astropixel processor, along with the settings he uses for each separate channel. I tried his method and I’m far far happier with the end result than I have been so far, so I’d recommend going and having a look, if it’s a process you’re struggling with like I was.

As with any images it’s taken several iterations before I’ve settled on something I feel is “right.” Of course that’s somewhat subjective when it comes to deep space astrophotography, and it’s a given that the final images aren’t going to please every single person. But I hope that as my knowledge and processing skills slowly improve, that the final image is something that can be appreciated for its majestic beauty. I’m not one that really likes all this star reduction and super smoothing of images, preferring instead a more raw natural look and feel.

Thank you for reading, and I’ll leave you with my final 11 hours on the Cygnus Wall in a faux SHO Hubble Palette. Clear skies all.

11 hours in faux SHO on the Cygnus Wall. 72ED with ZWO dual narrowband filter, and ZWO ASI183MC on EQ5 Pro

Update: 25th August 2022

After picking up another method of processing faux SHO images thanks to Astrobloke’s video, I’ve had another go at the data and have finally come up with an image I’m far happier with. Exactly the same data, just a different way of processing it. I’ve left the original version in this post in order to show that astrophotography is a constantly evolving process.

Much much happier with this iteration.

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