A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Brad Morris
Date: 2016 Jul 26, 14:50 -0400
The purpose of the glass is to diffuse the light applied behind it to make the scale easier to read.
Using a flashlight that projects red light will make the lines pop, when used at a very shallow angle to the scale. You look down at the scale while projecting the red light across it horizontally.
Why red? Because it won't bother your night time vision.
My Aunt gave me my Uncles 1850s vintage sextant.
It all works but it is very hard to read the scales.
Both scales are silver and I cleaned them very lightly with a drop of oil.
The vernier scale (the one on the index swing arm) looks better but the main arc scale is still very light.
It there some way to make the marking on these scales easier to read?
There is also a window for a small piece glass.
The glass is missing.
What is the purpose of the glass?