The Whirlpool Galaxy From The Backyard

Well it has been a long time since I’ve published anything to the site, but I’m going to make a concerted effort to get back on top of things, I just haven’t been able to shoot nearly as much as I wanted for reasons outlined below. The Whirlpool Galaxy was my latest target and to date this was the hardest image I have ever gotten. For some context, I got my new mount, the CGEM DX, and Celestron C8 back in August of last year. Since then, I have been troubleshooting and optimizing the rig nonstop and this is the very first successful image I got out of it.

My issues started with balance. The CGEM DX uses a thicker counterweight shaft than most other mounts and all I had was a 22lb weight to balance a C8 with all my camera gear on it. Unfortunately, all that other gear didn’t weigh out to 22lbs, so it never balanced. I eventually rigged a dumbbell weight onto the front of the C8 for an extra couple pounds and that worked… mostly.

The second major issue I had was guiding the thing. The C8 as configured for me is F6.3 and 1301mm as calculated by ASTAP. This means guiding is tricky because differential flexure starts to really make a difference. That’s essentially when the optical difference between your guide scope and imaging scope becomes so great that guiding drifts overnight. This was very present with a 50mm guide scope and I realized quickly that would be unusable. In the end I got an 80mm guide scope and that almost solved all my issues, but I was still left with some drift. In comes Flexure Correction, a plugin for NINA which is designed to solve this very issue. Long story short, it worked perfectly with default settings and I haven’t thought about it since. Best part is, it’s free.

Focusing a C8 is a nightmare with the stock focuser as well. The knob is small and small turns can make big differences in focus, which I solved by investing in a ZWO EAF, which also allowed me to automate one more thing.

The next piece of hardware I got was a ZWO EAF, which allowed me to fully automate my sequences and keep all my filters plus a dark filter in one enclosed place all the time.

The final issue I had was flat frames, which I’m still trying to totally work out. The white t shirt method completely broke down with this setup. It used to work great, but something wasn’t right and I still had dust and poor correction in my final stacks. At the suggestion of someone on cloudy nights, I bought a white square of acrylic, which has nearly fixed all my issues. I still have over and under correction in places, but the dust is gone and the remaining issues can be processed out in post.

All that being said, here’s my final image.

This image consists of 120 two minute luminance frames, combined with 45 two minutes RGB frames. The crop is really aggressive due to rotational artifacts from multiple nights of imaging (pro tip: don’t rotate your camera until you’ve completely finished shooting a target).

I processed it in Pixinsight using BlurXTerminator and NoiseXTerminator, the former of which is a fantastic new plugin developed to sharpen and remove focus and atmospheric issues in images. It does wonders for the final image and I would argue is essential for anyone beyond a beginner level of astrophotography. All individual filter stacks were given crops, BlurX, background extraction, and linear fits to luminance. They were then star aligned, cropped, and combined to form an RGB image and NoiseX was applied followed by the image being plate solved. I ran Photometric Color Calibration, followed by background neutralization and regular color calibration. I then did a soft stretch and ran a range mask to protect the galaxy and stars while I ran SCNR on the background. Inverting the mask, I applied curves transformations that allowed me to fine tune the color in the galaxy to be more natural looking and I also brightened things up. The final tweaks were star reduction using the EZ processing suite, histogram transformations for the background brightness, and some very cautious curves adjustments.

This image in total took two nights to shoot and 4 days to process to where it is due to trial and error and some processes taking literally an hour to run. The final image was exported as PNG for publishing.

I’m still working on a full process to get the stars to exhibit more saturated and natural colors as it can be difficult to achieve using a mono camera and filters, but when I figure it out I will for sure post a guide because it is something that I have been working on for a while now.


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