I processed the Tulip Nebula last year and was fairly happy with it. After posting it, I saw another version with a larger field of view and had some interesting OIII areas that were out of my field of view. I decided to shoot that area and make a mosaic. I had all kinds of problems with artifacts in my mosaic. I'd make adjustments to eliminate one artifact, then another would pop up. I got sick of artifact whack-a-mole and shelved the project.
I recently saw a video demonstrating the PhotometricMosaic tool, so I decided to give it a go. It worked the first time with no artifacts. With SHO images, I tend to stretch each channel independently before combining so I can get adjust each stretch to give me a better balance. The downside to this is you can get some strange looking stars, so this time I removed them, and then separately combined the original channels linearly, and used PhotometricColorCalibration, which sorta worked. I did a gentle stretch to the point where I wanted my stars - a lot smaller than with my other stretch, removed them and used them in my final image. Perhaps when it's back up, I might shoot some RGB for stars.
The original non-mosaic image is
https://www.astrobin.com/rg95yx/
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