Many moons ago, I played around with PyFITS which requires Numpy. I don't know how advanced it has become as I've succumbed to the commercial providers on a x64 windows platform.
http://www.stsci.edu/resources/software_hardware/pyfits
If you're looking for something commercial, there are a few out there. One that comes to mind is PixInsight -
http://pixinsight.com/
