The canon "Nifty 50" or "plastic fantastic" or "Canon EF 50mm f/1.8 II".
If you can't find one for less than $100 you're doing something very wrong.
This lens is possibly the single best 'bang for buck' piece of equipment available from Canon. It's fast, sharp and cheap, which makes it an essential part of my astro cupboard.
But I'll agree with Gordon, if you've got a 'casual grand' to spend, buy a tracking mount.
