Assuming you mean FITS when you refer to the weird file format, you may be interested in this (well-maintained, mature) Python wrapper library: http://docs.astropy.org/en/stable/io/fits/

FITS does a lot of stuff that PNG and friends can't, so it remains in use to this day.

If you're looking for astronomical data from Hubble (and some other space telescopes), you should check out https://mast.stsci.edu/ (or http://archive.stsci.edu )