NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Sextant Trivia: Index Arm/Mirror Offset
From: Greg R_
Date: 2006 Jul 27, 13:39 -0500
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From: Greg R_
Date: 2006 Jul 27, 13:39 -0500
OK, here's something that I've always wondered
about...
On every sextant that I've ever seen, the index
mirror is offset a few degrees clockwise with respect to the index arm itself
(i.e. they're not parallel to each other). Is there a reason for that (or maybe
it's just a tradition that survives to this day)?
The only thing that I can think of offhand might
have to do with the overall design scheme of the sextant itself (i.e. maybe
something I'm not seeing here that makes the manufacturing process easier)
- but the only thing that's obvious is that would move the index arc
itself more counter-clockwise (or more to the right-hand side as you face
the instrument), and I really don't see any advantage or disadvantage in
doing that.
I realize that the actual position of the mirrors
is really irrelevant to getting an accurate reading (and any "offset" of the
index mirror could easily be taken out with a corresponding offset in the
horizon mirror), but wouldn't it be easier to just make the index mirror and arm
parallel in the first place and be done with it?
--
GregR
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