I have been wanting a quality big zoom lens for several years but they are very expensive and out of my price range. They still are. I recently found a Minolta 500mm f8 Reflex Lens for sale on Craigslist that was in very good condition and at a reasonable price so I bought it. I was not really sure it would produce photographs that I would be happy with knowing all of the pro/cons of a reflex lens so I figured I could always resell it if I was not happy since the price I paid was well below what they normally sell for.
There is one thing that makes this lens unique compared to other mirror reflex lenses, Minolta somehow managed to get their lens to have AF. That makes this lens the only mirror reflex lens to have a working auto focus system, all other mirror lenses are manual focus only. Combine the AF with Sony's built in image stabilization and you have a nice zoom lens and high ISO's are handled pretty well in todays modern digital SLR cameras.
The Minolta 500mm f8 Mirror Reflex Lens
I have not taken the camera out into the field yet but have a few shots from the bay near my work. So far I am impressed with the lens, I think it is a keeper. All of these photos were taken handheld and have a slight bit of PP done, just a default sharpen/vibrance filter was applied. More photos and the EXIF info are in this gallery.