NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Robert Swartz
Date: 2021 Dec 7, 06:07 -0800
Re Kollsman sextants --I checked them at 0, 45 and 90 degrees. They are well built instruments with minimal mechanical deviation. The overhaul station usually zeroed them and my check showed at most 1 min. of arc error through the range.
Re WWII surplus sextants --I strip down the instruments, clean, adjust and lubricate them and fill the bubble chambers. I zero the instruments using my Link Sextant Collimator or the natural horizon of Lake Michigan on a clear day at the shoreline to eliminate dip error. Again, checks are made using the collimator at 0, 45, and 90 degrees. Most of the instruments hold + or - 1 min of accuracy through their range.
Regarding the 0, 45, and 90 degree checks: This was recommended by Ken Gebhart of Celestaire for bubble sextants. He used a three position collimator which he showed me for checking the Navy Mk Vs which he sold.
See pic. of Link Sextant Collimator:
