NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Timing noon.
From: George Huxtable
Date: 2002 Apr 12, 06:09 +0100
From: George Huxtable
Date: 2002 Apr 12, 06:09 +0100
In response to the following question about estimating the time of local noon- >"As I see it, no other input is required than altitudes of the Sun >measured >at suitably chosen times, a knowledge of the North-South component of the >ship's speed, and the rate of change of declination. Does Walter agree?" Walter Guinon said- >I think the E/W component of the ship's speed must also be incorporated in the >solution. Well, I doubt that, and invite Walter to reconsider his opinion. As I see it, Easterly motion, against the Sun, increases both the rate of rise of Sun's altitude before noon, and the rate-of-fall after noon, without affecting the symmetrical moment of noon itself. The maximum altitude will occur at the same moment for a vessel heading East as for a stationary vessel. Similarly, Westerly motion reduces those rates of change. So such motion has no effect on the result, though it may change the shape of the curve that Walter's proposed method is trying to fit. Can he persuade me otherwise? George Huxtable. ------------------------------ george@huxtable.u-net.com George Huxtable, 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. Tel. 01865 820222 or (int.) +44 1865 820222. ------------------------------
