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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Sextant with an umbrella
From: Peter Monta
Date: 2015 Oct 2, 00:02 -0700
From: Peter Monta
Date: 2015 Oct 2, 00:02 -0700
What's going on in this photo? Is the "umbrella" some sort of prismatic device for backsights??
My guess would have been a sunshade to cut down on stray light into the telescope, but Luc's links make the case for the dipmeter attachment open and shut.
Two pentaprisms might be a good way to implement it nowadays---a long prism would have to be custom-made, and mirrors could be knocked out of alignment.
Cheers,
Peter
