His 1/10000 revolution is going to give a spot motion of 0.2 inch at a
distance of 13 feet. He won't have any trouble seeing this with a
halfway-decent laser. If his laser has a divergence of 2 mrad full
angle, at 13 feet the spot is only a little more than 0.3 inches
diameter, and I'll bet he can see a spot motion of 0.05 inches with a
0.3 inch spot.

You're right that people don't generally realize how big and fuzzy the
laser spot is going to be, but in this case it should be no problem.

I would use an autocollimator or jig transit or theodolite if I needed
to resolve 1 arcsecond or 10 arcseconds, but he has to resolve only 130
arcsec. When I set up an autocollimator measurement I use a diode laser
attached to the autocollimator to get it roughly aligned; with the
target 13 feet from the mirror, it's easy to measure angular changes
quite a bit smaller than 130 arcsec using just the laser and mirror.

Don Holly

Richard J Kinch wrote:
Eric R Snow writes:


So, measuring the distance the spot travels will show how many pulses
should be generated.


This won't work with a simple beam. The laser spot will inevitably be many
times the size of the motion of the spot you are trying to measure. We
have hashed this over and over with people who speculate they can align
their round-column mill drills using a laser.

I'm always surprised by people who think laser pointers have near-zero
angular diameter. Not the case.