Re: Sextant Error and Whole Horizon Mirrors
Subject: Re: Sextant Error and Whole Horizon Mirrors
From: Aubrey O'Callaghan (ocallaghan@XXX.XXX)
Date: Wed Jul 10 2002 - 08:18:17 EDT
One of my sextants is a Cetus Russian sexant.
The magnifying telescope has all the bells and whistles referred to by
Bruce, inverting image and parallel wires.
However it has a split mirror.
Aubrey.
At 21:03 09/07/02, you wrote:
>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
