I'm hoping someone can help me. I live in a Bortle7/8 urban area and have to use narrowband filters. Over the past few nights, under 90%+ full moon, I've gotten the artifact shown in the attachment. I believe it has occurred without the moon being present but I have not checked.
Gear - ASI1600MM, CEM25P mount, 100ED with .75FR, ASIair Pro, Starizona filter slider, 1.25" 6nm Astronomik Ha, Oiii and Sii filters
240sec subs, unity gain, binned 2x2, sensor temp -20°C
All lights in the immediate area of my strata unit were turned off for the last couple of nights but the Ha session only had one neighbor's light turned off.
The target was NGC7380, the Wizard.
I've tried to ensure there was no sag in the optical train. I could see no obstacle in that path.