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 10, 09:31 +0100
From: George Huxtable
Date: 2002 Apr 10, 09:31 +0100
Walter Guinon said- >When declination and Latitude are changing appreciably perhaps the most general >method of estimating the time of local noon is: >1) Take altitude measurements of the sun when you can, hopefully between >sunrise and sunset. >2) The clock time of noon is that which gives a least mean squares fit of this >altitude/time data to the computed altitude at the DR position. George Huxtable responds- This, to me, is a bit too general to be really helpful. I wonder if Walter Guinon could be a bit more specific, please, about points 1 and 2. Should the navigator spend the whole day measuring, or are there times that are more useful than others? What is the "DR position" that he refers to, and what measurements has it been derived from? Having chosen that position, how does he make the least-squares fit? 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? ------------------------------ george@huxtable.u-net.com George Huxtable, 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. Tel. 01865 820222 or (int.) +44 1865 820222. ------------------------------
