)) Cheap 500mm Fun ((
I went down to school to register for next semester, still have to go back Monday to finish.  I bought a Phoenix/Samyang 500mm mirror lens for $40 today off a friend.  It only has one aperture, f8.  It's fun changing the iso and shutter speed to compensate for no aperture.  And because I have a digital camera, the magnification of the lens is multiplied to approximately equal an 800mm lens! It doesn't focus clearly.  It's a very compact lens (4 1/2 in. long) and I'm told they sell for around $70 new on ebay.
[My locker is somewhere around the strange, almost-focused point.  Shoddy equipment and materials are sometimes used to create a fine arts look.  (Why is that?)]