Terry, I agree, the Canon EF 200mm f/2.8 L series is a superb lens, my favourite for terrestrial and most certainly astro work.
I've used it for astro imaging and have been very impressed with its performance.
Looking at it's
MTF characteristics one can see why it performs so well, it's approaching (but not quite) the performances achieved by the awesome super telephotos like the
EF 300mm IS f/2.8 L, and
EF 400mm IS f/2.8 L (if you can afford them !).
Another surprisingly good lens is the
EF 180mm f/3.5 L Macro. Superb for Macro and also a fantastic telephoto lens too.