A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Andrés Ruiz
Date: 2008 Sep 23, 09:49 +0200
I say in [NavList 6290]:
The calculated star-star distance is compared with the observed one to obtain the sextant error, that is the index error plus the instrumental error inherent to the sextant.
and as Frank says in [NavList 6302], the objective is to build a table for the sextant error in all the arc from 0º to 120/130º
In a museum I have seen a XIX century sextant with two table, one for the index error and another for the excentricity.
Also to practice with the sextant for fun.
Bill, [NavList 6295], the program runs only under windows XP, 98, 98, 200, NT, sorry.
Frank: [NavList 6303] “I think a title that would make more sense (at least in English) would be 'sextant calibration by star-star distance' or 'arc error by star-star distance'.” – Yes, I think is better.
[mailto:NavList@fer3.com] En nombre
de Gary LaPook
Enviado el: lunes, 22 de septiembre de 2008 19:52
Asunto: [NavList 6294] Re: Index error by a star-star distance
O.........K............. I guess I don't
get it. Why not just sight on one star which should have a zero altitude
difference between the two images of the same star. Where is the advantage in
using two stars? In addition you would not be determining "index
error" since the measured error would be the total of index error
and "arc error" and you could not determine the contributions of each
of these components. Star to star distance can be used to check for arc error
but only after index error has been determined by some other method since this
value must be subtracted from the measured star to star distance before
comparing the measured distance to the computed distance thereby
determining the arc error at that point of the arc.
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