These fringes are are think a different source from the usual newton rings, the tilter works very well for the NR but I’m not sure about Moire fringes.....May be a processing/ acquisition software issue???
I wonder if it would be worthwhile moving the sun around the frame while capturing? The FPS will be fast enough that it won’t have an affect on any frames and if this is some kind of fixed pattern noise it should help to remove it while stacking.