NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Brad Morris
Date: 2012 Dec 28, 12:54 -0500
Hi Randall
The objective in measuring the altitudes is to form an assessment of the correction in lunar distance due to refraction.
Since the true altitude is a straight-forward application of spherical trig, we can obtain both the true (uncorrected) altitude AND estimate the refraction for each, without actually measuring them! With these (and other factors), we can clear the lunar distance.
Its perfectly valid.
Frank's online calculator gives you the option to measure the altitudes or to just calculate them. Frank would hardly let you have that option if it wasn't.
Kind Regards,
Brad
In an article about Lewis & Clarks navigation I see references to a Lunar distance method without real time altitude measurements being required. Instead they use a calculated pair of altitudes.
"Patterson’s Problem 4th, which is also a part of his notebook,
describes a method of calculating the altitude of a body at any instant
using the known latitude of the observer; the estimated longitude; a
Greenwich time for that instant calculated from the estimated longitude
and the difference between the watch time of the instant and the
watch time of noon (with a correction for watch rate).
Although this is a reasonable procedure and gives excellent results,
it seems to have been controversial at the time."
Richard S. Preston, Physics Department, Northern Illinois UniversityCan anyone tell me if this is valid?
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