NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Error of Perpendicularity
From: Robert Eno
Date: 2006 Apr 17, 13:25 -0400
From: Robert Eno
Date: 2006 Apr 17, 13:25 -0400
I recall asking this question before so if I did, I
apologize for repeating myself. It seems to me that I never received a
definitive answer.
What is the practical consequence of the index
mirror not being perfectly perpendicular to the frame of the sextant? I have
dozens of navigation texts, some of them dating back quite a few years and while
all of them direct the navigator to check for it, none of them reveal the
consequences of not having the index mirror perpendicular to the frame of the
sextant.
Furthermore, I know of a few techniques for
adjusting the index mirror for perpendicularity, including the eyeball
method and placing objects (such as a pair of dominos) of exactly the same
height at opposite ends of the sextant limb but it seems to me that these
methods are rather coarse and not nearly as precise as those for reckoning index
and side errors.
Any comments on this most fundamental topic are
welcome.
Robert
