Hi Bill, you posted your reply while I was typing so I did not see it
It is "Orion extra narrowband imaging filter", not ultrablock. My bad, apologies again for starting people on the wrong track.
No delamination is visible, the filter looks OK.
I am suspecting tilt now, have to do a bit of reading how to quantify it and also about the Skywatcher ED80 Crayford focuser and its week points.