Ooh, great question. Usually fractions (~1/20th?) of a turn for alignment, it’s hard to go below that since the mounts are so small and the springs don’t have the tension to keep it super stable. (This is plenty for such a “coarse” set up like a Michaelson but might not be up to par for more delicate ones. This can be improved very easily but it was enough for this experiment!) If you want to observe something on the outputs, you have to do something like exhale on one of the arms or put a soldering iron near one of them—merely touching one of the screws gives you indiscernible output, even if the mirrors are aligned.

Very interesting re: JWT, I will definitely take a peek, thanks !