Here are the FITS files from data release 7 of the Sloan Digital Sky Survey about 17 arcminutes wide with the globular cluster Messier 3 in the field. There are field stars for sure but lots of data on M3 to mess with. I downloaded all the data files for each of the U, G, R, I, and Z filters used by SDSS telescopes.
https://jimmynewland.com/m3/m3-sdss-g.fits
https://jimmynewland.com/m3/m3-sdss-i.fits
https://jimmynewland.com/m3/m3-sdss-r.fits
https://jimmynewland.com/m3/m3-sdss-u.fits