Sure Sharp knife edge focuser with Olympus OM T-Ring adaptor. I used it with the Lumicon Giant Easy Guider (also for sale). Get the best possible focus for astrophotography using the knife edge focusing technique.
This focuser has been modified from what came originally with the Sure Sharp. The Ronchi screen has been replaced with razor blades to greatly improve accuracy. This modification can be changed back with minimal trouble if you choose too, but I don’t have the Ronchi screen anymore. I found the razor blades far more accurate, although a bit more difficult to use, since a focusing star must be centered.
My experience in the field lead me to making this change to the Sure Sharp, and in my opinion is an improvement on the original design.
Was asking $125, now asking $95.