Weird shaped stars...look like UFOs?

[vlaiv]

9 hours ago, oymd said:

Here is the stacked TIFF file from DSS.

As far as I can see - stars now do look better but not quite yet there - so we know that at least part of it has to do with guide performance and stacking parameters. Some subs are probably too distorted and if you manually (or automatically) remove those - things should improve somewhat.

Red channel now looks normal, but there is some distortion in green and blue.

It would be worth first checking what sort of image you'll get without that filter (to see if it's causing problems) and further investigating optics itself by taking some out of focus images of bright star (small defocus so that there are still rings visible).