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?)]