The performance of the autocollimator is being evaluated in a laboratory setting.  It’s an image as of the autocollimator in the lab on a ThorLabs adjustable 2-axis stage. This stage was affixed to the laboratory workbench with clamps and used to point the autocollimator towards 2 diameter front-aluminized mirror. This mirror was generally positioned 8 meters away from the autocollimator to match approximate distance expected to separate the autocollimator and the mirror on the prototype (Cherenkov Telescope Array) CTA-US telescope. The mirrors was contained in a Newport U200-AC kinematic optical mount which via optical post to a breadboard, which turn was clamped to another laboratory workbench. We attached Newport Sm-13 Vernier micrometers to the mount which have to 10 microns graduations and 1 micron sensitivity with the Vernier scale. The distance between the micrometers and the pivot point its 60 mm.

The autocollimator is being used to measure the tilt of the mirror from 8 meters away. For each mirror tilt, the x and y coordinates of the autocollimator spot centroids needs to be collected for about 10 seconds at a rate of 1 Hz (Hertz). The exposure is set to 0.04 seconds, so the sampling rate could be much faster. Setting the exposure is manual.  The x and y pixel positions is then used to compute the angle of the mirror. We only need to adjust the tilt mirror along one rotation axis at a time, and stability of the mirror mount and the rotational alignment of the autocollimator should be good enough that other axis is never varied by more than about pixel 1.