Certainly does sound like you have the right filter in place Daniel. My next question would be is there any chance that you have a light layer of dew building up on the filter ? I had this happen on my filter on my DSLR. I would have thought in therory that in a refractor system, that should be mostly sealed off but I guess if there is moisture in the focuser when you put the camera in it is in theory possible. This would cause a defraction of the light causing the bloat. Can you maybe compare an early sub and see if the “ iris “ is there ? If that isn’t happening, I’m really not sure but you’ve posted an interesting problem and I’ll be watching keenly to see what the outcome is.
Ryan
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