Date Posted: 1/26/2024
Date Taken (Ha): 6/7/2020, 7/2/2020, 7/11/2020
Date Taken (LRGB): 4/19/2021, 5/12/2021, 5/13/2021, 5/14/2021
Scope: Planewave CDK 12.5 f/8, 2541mm
Camera: SBIG STL-11000 with Astrodon Tru-Balance E-Series Gen2 filters
Temp: -15C
Mount: Losmandy Titan
Guiding: On-axis via ONAG-XM and SX UltraStar at 2541mm. FocusLock real-time focus for focusing.
Exposure: LHaRGB, 320:705:185:180:180. Luminance 10min unbinned; RGB 5min binned 2x2; Ha 15min unbinned.

Calibrated and Stacked with CCDStack2. Processed with CS4.

NGC 6823 is the open cluster in this picture. Technically, NGC6820 is a small reflection nebula near the cluster, but it's not really visible in this image due to some processing mistakes. The larger emission nebula is commonly referred to as NGC6820, but is also catalogued as Sh2-86.

I found this difficult to process, I'm not very good at Ha processing/blending; in addition, I was experimenting with Starnet++, to remove stars from the image and better stretch just the nebula. Despite that, many of the fainter stars re-appeared when stretching, with a strong reddish bias. The Ha signal was much stronger than the visible red. In blending, I kept ending up with less-than-pleasing nebula colors, unsightly halos around many brighter stars, or both. Eventually I gave up, and this was the version I settled on.

Update 1/26/2024:
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I was never happy with the colors, brightness, or contrast of the original image. I re-processed it, this time using StarXterminator on the Ha, Luminance, and RGB images to stretch the starless images separately before combining them. I ended up with mostly colorless stars, so I used the stars-only version of the original to restore some of the star colors. The result is a significant improvement from the original image; the original is still in the Nebulae Gallery for comparison.