A macro lens examining our galactic centre :-) See the Lagoon and Trifid in there?

Note: You can autofocus any Canon tele of 100mm or longer focal length on a bright star or planet. I found this more reliable than manual focus, and certainly much quicker than using a focus routine with feedback on a laptop. Unfortunately for shorter lenses you have to use the feedback method, but even this is a breeze if your DSLR has LiveView.