NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Working a lunar
From: Hanno Ix
Date: 2009 Aug 5, 22:57 -0700
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From: Hanno Ix
Date: 2009 Aug 5, 22:57 -0700
Gentlemen: I am a novice to CelNav, and I certainly have no experience in lunars. Some algorithm occurred to me, though, that I would like to share and discuss. However, given the age of this business, if it is a valid one I doubt it is new. If anyone has seen it before, please let me know, so I could read up on it. The objective is to find GMT and location. Let's make a Gedanken experiment: A ship reaches land of unknown coordinates. Land makes it practical for the navigator to measure the meridian passages of Heavenly Bodies rather reliably. Given GMT, he can calculate LAT and LONG. (One shot method.) But now we pose GMT as unknown. Sitting on land, measure the meridian passages of, say, sun and moon which moves. Can I find GMT, too, using the now available data not using the classical moon distance methods? If I see things right, there must be a LOP which connects all locations on Earth with a given, fixed difference DT between the meridian passages of sun and moon. However, along this LOP, the same DT occurs at a different GMT. In this scenario, the LOP referring to a given DT is pre - calculated, listed in an almanac and annotated with GMT at each LAT. So, by having found the LAT before we just read the GMT of the DT-specific LOP. There is another opportunity: By accepting preliminarily this GMT, we can calculate LAT again, namely from the meridian passage of the MOON, and compare both values found. If there is a gross difference we must have made an error. This, by itself, would be of value. Otherwise, though, we have good reasons to accept the GMT we found. I appologize if I am talking about a method I have not gone through myself yet! I fear there is a hick-up in this somewhere. But I would like to hear the critique of you specialist navigators before I spend alot of time trying to do something long known as wrong. If, however, you find it sound, and has not done before I will pusue it. Best regards --- On Sun, 8/2/09, Paul Hirose <cfuhb-acdgw@earthlink.net> wrote:
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