A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Geoffrey Kolbe
Date: 2020 Mar 4, 23:06 -0800
Igor S. said:
"Leveling is performed with the help of circular bull-eye level (from www.leveldevelopments.com) by placing it at the middle of the mirror face."
I had a look at that bulls-eye level and the precision is 5' of arc for 1mm bubble movement. I would suggest that this is going to be a limiting factor in the accuracy of any measurements you take with this AH.
Remember, while the error in taking the angle measurement between reflected and direct image of the celestial body halves - because you then halve the measured angle to get the measured altitude - the error in the levelness of the AH does not halve so that carries though to a direct error in the measured altitude.