This lens makes a great cap for a DSLR body.
As others have said, it's pretty much a throwaway lens, which just happens to be remarkably sharp for the price paid.
Your next step would be to move to the 50mm f/1.4 USM or the 50mm f/2.5 USM macro. They are of a far sturdier construction with more lens elements. The 50mm f/2.5 USM macro is a very, very slow focusing lens. But, most of the time, we're hooking up our cameras to computers to do astrophotography, anyway, so, it should be a no brainer to fire up EOS Utility, go into Remote LiveView and control the focusing from within EOS Utility itself: set lens to AF, load EOS Utility, select Remote LiveView/Shooting, click the 200% box, press the buttons for focus/fine focus until the star is in focus (typically, this means being on either side of red/blue chromatic aberration). Once the star is in focus, ensure you switch back to MF on the lens so you don't inadvertantly shift the focus from the computer.
Happy shooting.
H