Ed - You may be right, I claim no expertise here. I just didn't like the idea of focusing with a loose mirror then tightening the mirror down, then slewing to another sky location and doing it all over again when I'd rather be sitting in my warm den. The crayford solves that problem. Now I open the roll-off roof and take the dust cover off and don't go back until it's time to close everything down for the night.
