Hi David:
I just found Jim Misti's image data the other day. He's uploaded TONS of stacked LRGB(H) FITS files:
http://www.mistisoftware.com/astronomy/index_fits.htmI've only worked on one so far, but it was definitely a good challenge sharpening-wise, compared with my slightly undersampled setup, or with Hubble data. Speaking of Hubble data, the MAST archive is a great source for that, and it's a LOT of fun to process:
https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.htmlThe challenge with Hubble is figuring out which target/files you want, and then removing artifacts. At least, that was the hardest part for me!
Have fun!
CS,
Mark