>>2961647mirrorlens guy reporting in
Disregard the haters, catadioptrics *can* produce very decent images. Some don't some do, depends on the lens. Yes they are a little soft and lacking in contrast, but at least a little of that is due to the sheer amount of atmosphere it's seeing through. Buy a decent lens and you'll easily be able to adjust it in post.
I own all of these:
ZM-6A 6.3/500 Mirror Zenit Tele Lens M42
Very good. Big, heavy, easy to disassemble. Often comes with rear lens element mis-assembled and therefore people think it;'s soft as fuck. Trivial to fix.
http://oh-hi.info/tech/A0000084-512px.jpghttp://oh-hi.info/tech/100_0178+100_0181-y800px.jpg1st favorite
Tamron Adaptall-2 SP 500mm f/8 Mirror (55BB)
Little, light, nice focusing helicoid. Near focuses at 1.75m, which is really useful.
Adaptall2 mount, so fits every camera ever.
2nd favorite
Image related to soft/unsharp comment
http://oh-hi.info/tech/ProcessingNotes_00088894-y600px.jpghttp://oh-hi.info/tech/100_0178+100_0181-y800px.jpghttp://oh-hi.info/tech/A0003642-y600px.jpgSigma 600mm f8 mirror
Old, big, very light, not bad, but not great. Most of the currently manufactured chinese knockpoffs and bower lenses are copies if this design.
Also there are two variations of diameter. One is 120mm or so, the other is smaller.. for minolta iirc.
Front mirror reflector separation seems fairly common and hard to detect by average bozo.
http://oh-hi.info/tech/A0003633-jpg88-crop1to1aty1800-y1800px.jpgAvoid.
SMC Pentax Reflex 1:11 1000mm
Good lens. Too big for almost everythng.
http://oh-hi.info/tech/C00002025-y720px.jpgMTO-11CA 10/1000
As good as the pentax. Slightly heavier, bigger. Built to be disassembled. Good 1/4/ and 3/8 tripod mounts on 2 sides (4 holes). Stiff to focus.
http://oh-hi.info/tech/A0003359-y600px.jpgTamron 350mm f5.6 (06B )
Excellent IQ for a cat. better off buying a regular 300mm with autofocus though. EXPENSIVE/RARE. Incredibly small/light.