Are the outer stars distorted due to needing a field flattener?

[Trippelforge]

My son and I imaged the bubble nebula last week and once processed I noticed the outer edge stars "streaked". Considering the ones in the center are sharp, I assume it wasn't a tracking issue. Are the images coming out like this due to needing a flattener? Or could it have been caused by something else? Thanks!

Edited November 29, 2023 by Trippelforge
Image is being weird

[The Lazy Astronomer]

If you don't have a flattener already, then yes.

If you have a flattener, then your backfocal distance is wrong (camera is too close) - see below:

[Trippelforge]

Thank you very much! I do not own a flattener, it's good to know about the distance so I can tweak one to get it correct.

[ollypenrice]

2 minutes ago, Trippelforge said:

Thank you very much! I do not own a flattener, it's good to know about the distance so I can tweak one to get it correct.

Yours is the first of the two scenarios. This is actually good news because the other source of elongation, besides tracking, is tilt - and that's a pain to sort out. Yours is the nicer kind of problem to have!

lly