For a project I am working with data from the SDSS. Here is a link to the field I'm interested in:

SDSS Run 6505, Rerun 648, Camcol 4

I am using the G and R corrected frames, which open up fine and look like a nice star cluster in Maxim Dl. The problem is, the photometry tool won't open them. I tried re-naming them and re-saving them, but that didn't work. I think maybe it has to do with the header file, but I would have no idea what to change.

Can anyone help me out?