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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Noell Wilson
Date: 2025 Nov 19, 08:41 -0800
I don't remember ever seeing a vernier sextant labeled with seconds. I think I remember seeing some micrometer sextants with the vernier scale next to the wheel optimistically labeled 0 to 60.
While the vernier scales don't say "seconds", they lead you in that direction with their divisions. Minutes on the arc are often divided into thirds and fourths - easier to think of a 60 scale in 20 or 15 minute intervals. The verniers would read 0 to 20 or 0 to 15 again, easy to divide into 60 second parts.
Attached is a photo of the vernier from a ~1900 C.Plath, SN 4040, with the arc divided into 1/6, or 10 minute, intervals and the vernier divided into 1/6, or 10 second, intervals.
A "reading of 10 seconds", and some other things, were required for English Class A sextants.
