Before I start randomly messing around with my imaging train and make things worse, I thought I'd reach out to the experts.
I started working on a narrow band image of the eagle nebula last night by shooting HA. I noticed elongated stars at a weird angle in the top right portion of the image. The rest of the image looks OK to me. I've had some flat field issues in the past with the stars streaking radially outward, but this is different. I checked the individual subs and they show the same issue. Do I need to tweak my field flattener / imaging train distances? Could my filter stink? Any ideas?
My equipment is:
Orion Atlas mount
William Optics ZS73 with the WO non-adjustable field flattener
ZWO EFW with the basic 31mm filters
5 min subs, with dark, flat, & dark flat calibration all taken last night.
Guiding was good with a 50mm scope and ASI120mm.
Here is the uncropped image (calibrated and stacked) and a zoom in on the upper right and lower left.