Beautiful. I can't begin to process images to the same level to try a mosaic.

You might try downloading the trial version of Registar. It is supposed to auto match mosaic images of differing scales. Kind of pricy and since I can't process them to the same level I haven't paid. I did try the demo (doesn't save) and it did a great job of matching to frames taken at different image scales due to being taken at different temperatures. One was a good 20 pixels larger than the other in scale and it merged them fine. My matching processing was lousy so never went any further. You have that issue solved so it may work for you.

Rick