A few options spring to mind.
First: Fasten an inclinometer to the backside of the mirror. This will give you an analog signal proportional to mirror tilt. Then use any standard process controller for set point control for upper and lower limits. This also allows the option of ramping the travel speed up or down for gentler starts and stops, and shorter travel time.
Second: Use any IP68 sealed proximity switch adjusted to operate at desired location.
Third: Clippard along with the rest of the pneumatic and hydraulic component manufacturers make manually operated control valves. Use a piston style switch to supply or release fluid pressure when the mirror carriage is at its desired position.
Fourth: Attach a sealed shaft encoder to the acme-threaded shaft and generate pulses to count revolutions to determine upper and lower travel limits. Omega has all sorts of controllers to handle the pulse counting and limit set points.
LarryC
