there a numerous reports of halos around bright starts with the asi2600, and/or the chroma filters. I suspect that is far more likely your issue and not collimation.

https://bbs.astronomy-imaging-camera.com/d/12719-halos-in-my-new-asi-2600-mm-pro


https://www.cloudynights.com/topic/809042-5nm-chroma-halos-are-these-from-the-filters/
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