For my current astronomy class, I'm supposed to look at several Mac- and/or PC-based FITS image viewer software packages and see how they work. Are there any ones that I should be sure to look at (or be sure to avoid)? Is this list current and authoritative? (Note that these packages need to be free unless there's one that's just the absolute standard and is definitely worth paying for.)

Thanks.

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Everything I need to know I learned through Googling.

I'd recommend ds9, which is on the list you quote. It has versions to run on Mac OS, Windows, and Linux. It is often used as a graphical interface to IRAF, so if you decide to move to more sophisticated analysis, you'll be familiar with part of it.

Like Stupendous Man said, ds9 is available for PCs and Macs. I've got it on my desktop computer at home, which is running Windows.

For Mac, they now have a Ds9.app. You need to have X11 installed, as it is an X-windows tcl/tk program. It's nice to have this as a .app, since you can associate FITS files with it in Finder by default. You also don't have to launch it from the command line.

If you want to do some fancier FITS manipulation, you can install the full FTOOLS suite put out by NASA's HEASARC. These are mostly command-line tools that run in terminal or xterm. The most useful one for your purposes is a viewer called "fv"; that's an X program so you need X windows as well. This can run under cygwin in windows as well. fv allows you access to all the data and image arrays in a FITS file, with graphing and display abilities.