[pmrid (Peter)]

I've been working my way into OSC imaging using different SharpStar 94EDPH and 61EDPH APO refractors and Optalong L-Enhance and L-Extreme filters.

I'm finding these odd artifacts in my images and can't put my finger on a cause.

They are basically rings around star cores - and they are across the whole image although more prononced in the edges and corners. I've encountered them using Flattener/Reducers and without.

I am using ZWO filter cartriges/drawers and I've tried moving them up and down the backfocus 55mm space but wth no difference.

I focus with ASIair Plus and with a Bahtinov mask with no difference.

Exposures have been 180and 300 seconds with no appreciable differnce.

A couple of extreme crops attached as examples.


Any thoughts?