NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Peter Fogg
Date: 2007 Feb 15, 15:05 +1100
Dan Walden wrote:
Many of the astronomy and navigation
texts from the 1800's ... have references to longitude by lunar altitudes. Since this
was before LOP, most discuss only longitude assuming latitude by one
of a number of other methods ...
Position lines (LOPs)
are not a necessary part of the process of determining time/longitude via lunar altitudes.
Watch Correction (WC) and Longitude can be
obtained simply by using Calculated and Observed Altitudes (Hc and Ho) as
follows:
Moon(UL) etc
Watch Time WC Longitude Hc Ho Intercept
1. 9h 07m 55s 0 W15d 22.5m 37d 38.9m 37d 36.5m A2.4m
2. 9h 07m 55s Slow 20m W20d 22.5m 37d 47.2m 37d 36.5m A10.7.4m
Let G = Hc1 Ho = 2.4
Hc2 Hc1 8.3
Watch Correction
G x 20m = 5m 47s Fast
Longitude
W15d 22.5m G x 5d = W13d 56m
The results are identical to those given earlier.
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