Mabula,
Yes I like to get straight in there and test the big mosaics ?
I don’t quite understand the Thin Plate Spline bit. That sounds like a method to calculate the registration for the panels.
So let me mention where the frames came from
1) FITs were calibrated in AstroArt 5 with Darks and Flats applied here to stack the master 4 hr files.
2) Once I had the master frames for each panel, I opened them in PI, Cropped any border from the stack, then ran the DBE process to remove any gradients and vignetting. (I have all 25 frames without the DBE which I can mosaic in APP to test v the DBE version)
3) So PI has not registered these panels to each other. They have only had the DBE gradient removal performed on them.
There is approx. 15-20% overlap on the frames. Or at least I thought there was. The gap on the bottom row surprised me, the rotation effects around Polaris is evident as it seems to compress the top row frames. I will re-run the 25 with your suggestions and see how I get on.