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Subject: Re: Sextant Error and Whole Horizon Mirrors
From: Bruce Stark (Stark4677@XXX.XXX)
Date: Tue Jul 09 2002 - 21:03:17 EDT
Chuck-
The only way I know of for sure to overcome the problem you are talking about
is to have one of the old-fashioned sextants or circles with an inverting
'scope. I've never been so fortunate as to use one but, besides being more
powerful and having a wider view, the inverting 'scopes had parallel wires in
the field of view so it was easy to keep the objects in the middle while you
made contact.
The problem you are describing is the problem of keeping the plane of the
observation parallel to the plane of the instrument. It's not much of a
problem for small angles but gets bad with wider angles. If you have a copy
of my "Tables for Clearing" look under "Odds and Ends" for a discussion of
this, and a table showing the effect in different situations.
It's also what I'm talking about in the last paragraph of that July 7th
posting. It seems your experience and conclusions are about the same as mine,
though my sextant isn't whole horizon. I hope other members will experiment
too.
Bruce
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