NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Rust's diagram for computing azimuth
From: Peter Fogg
Date: 2007 Oct 9, 08:12 +1000
From: Peter Fogg
Date: 2007 Oct 9, 08:12 +1000
Thanks for that diagram, Gary. I guess that the sine formula lends itself to tabular or graphical expression. If the tan formula was capable of being similarly expressed, then someone would already have done it? Or is it just waiting for some clever person to figure out how to do it?
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Gary LaPook writes:
Attached is Rust's diagram for computing the azimuth of the sight which
was included in Weems "Line Of Position Book," 1927. It was developed
using the sine formula. You enter on the left with LHA and go to the
right to the declination then straight up to the altitude then to the
right to the azimuth. Also included is a table used to determine in
which quadrant the azimuth falls when the body is close to east or west.
This diagram can be used with any set of tables, H.O. 208, H.O. 211,
etc., and the extra steps used in those tables to compute the azimuth
can be disregarded.
The shape of these curves show the potential loss of accuracy using the
sine formula as the azimuth approaches 90º as the altitude curves become
almost vertical and only slight changes in altitude results in large
azimuth changes.
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