>>3595872>Nikkor 500mm feflex f8...I assume that the Nikkor is much better than the Tamron? The prices look good on ebay; for the older ones with the orange ring. Had I not bought the exact one in the OP I'd have bought that one had I known about it at the time.
The one in the OP is extremely vibration sensitive. Here's a vid using it on a tripod standing along with a gentle breeze. This is without tripod stabilization weight of any kind though. I really thing these need to be used with in-camera stabilization for best results. Also, the DOF on the Opteka one is thinner than the Russian and Nikkor ones. So, it is more difficult to nail focus.
