Thanks Shelley and Wayne.
Well, after finally catching up on a bit of sleep I got around to processing my original wide field photo at high resolution with a manual alignment and stack of 3x 301 sec frames - I found another one that I'd missed earlier
- in Photoshop with a drizzle factor of 3x.
Processing 21 megapixels x 9 (drizzle) x 3 subs = 567 MP using my 2009 era 13" MacBook Pro was a bit of a struggle, but it survived. The drizzling and third sub resulted in a noticeably smoother and richer image than the one in my original post.
I threw a roll of 24-inch wide Hahnemuhle Monet Canvas into the printer and ran the photo off as a 24x38 inch (61x96 cm) print. The attached pic shows the actual image pixels (left) and a quick iPhone snap of the canvas being printed (right). Hooray for colour-managed workflows
The comet itself ended up about 20 cm long in the print.
I just have to seal the print with a protective spray, send it off to my framer for stretching, put a nail or two into a wall, and she'll be all good to go
