NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Brad Morris
Date: 2012 Dec 14, 11:13 -0500
Hi John
In order to correct for refraction, your position on the earth and the time must be known, such that the uncorrected for refraction altitude can be known of the star(s) in question
I do not understand how this book can acccomodate for your position & time.
Kind Regards
Brad
There's a book called "Celestial Navigation in the GPS Age" that lists the distances between 12 star pairs.
Since these distances are corrected for refraction, tables are entered with the altitude of each of the stars in a given pair. The data should be useful, even for observers that lack a good horizon, since the refraction corrections are rather insensitive to the star's altitudes (as can be seen in the tables).
The star pairs are selected to give arc distances that range up to 113d for checking arc error on the sextant. Also consideration is given to selecting pairs that are visible throughout the year over a range of observer locations. Furthermore, they're selected for having very slow movement among themselves (called proper motion), so that their star-star distances won't change significantly by 2025.
However, the distances are not corrected for aberration (the effect of the observer's velocity perpendicular to the light ray from each star). This effect can range from zero to a maximum of 0.56' of arc, which occurs only under very special situations and for large star-star distances. The tables should be handy for practicing sights and checking sextants.
The "Revised and Expanded" edition of that book is recommended,
Zubenelgenubi #39
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