NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Robert Swartz
Date: 2022 Nov 5, 20:03 -0700
At night or in darkness, close the sun shade on the horizon tube, light the bubble light; use indirect viewing method making sure the bubble image projects on the mirror.
Use a collimator set to 0 deg. or construct a target at least 500 ft. away at the same elevation of the sextant in a mount.
Set the sextant dial to 0 deg, 0 min.at the lower stop. The gross adjustment is done by moving the mirror w/ the averager removed and the mirror shaft nut loostened.
The 0 datum image should be on the right or left side equator of the bubble when the bubble is in the center of the field of view.
For fine adjustments, use the adjusting screw on the top of the mirror.
Do not use the horizon tube to zero the sextant, you will probably get a false reading. This applies to the use of the natural horizon as your 0 datum.
For the life of me, I can't figure out why B&L put horizon viewing optics on an aircraft bubble sextant. Any answers?
