A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Robert Swartz
Date: 2015 Dec 28, 15:08 -0800
There is nothing in the Link literature on the mounting order of the sun shades,
Both bubble chambers should have Bristol set screw filler plugs with either small ball bearings inserted or, in the case of early A-12s, points on the end of the filler plugs.
Refilling bubble chambers was part of routine maintenance of bubble sextants--The integrity of the filling depends on the seals and the tightness of the filler plugs (which I also seal w/liquid shellac) after filling the chambers w/ xylene.
Your sextant is severly out of calibration and probably needs an overhaul. I calibrate the sextants I sell to 1-2 minutes of arc using a Link Collimator. You can use the natural horizin at the shore of a large lake or the sea under calm conditions as a zero datum. You can also use Polaris from a known latitude (requires correction tables in the Nautical Almanac).