Hooray! Now I have the r and g magnitudes, magnitude errors, and positions of all stars in 50 simulated dwarfs with the same absolute magnitude and scale size as Andromeda XIX!
I was able to finish the code and debug by the time Beth came to lab this afternoon, which felt like a huge success, given how stuck I was this morning.
NEXT STEP: putting these fakes into RCS2 (and eventually SDSS) data! I've started the code for that, and hope to complete it tomorrow morning.