NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: instances of the use of "horizon grazing" technique
From: John Huth
Date: 2009 Oct 23, 14:06 -0400
From: John Huth
Date: 2009 Oct 23, 14:06 -0400
Brad -
Exactly!!! What amazes me is the long shelf-life of these.
For the record, I actually tried this technique as an experiment in late October last year, and was off by 300 miles of latitude - it is only "reliable" (and I use the word advisedly) near the solstices. My house had a good view of the horizon of both rising and setting sun, and, yes, I applied a correction for refraction, as if that mattered.
Also - for the record - in the approximation where the solar declination doesn't change over the course of 24 hours, the equation is:
Lat = arctan( (cos (d/2))/tan(decl))
Where d = length of day in degrees or radians. It obviously breaks down when decl=0. Try remember this and calculate this on a life raft.
John H.
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Exactly!!! What amazes me is the long shelf-life of these.
For the record, I actually tried this technique as an experiment in late October last year, and was off by 300 miles of latitude - it is only "reliable" (and I use the word advisedly) near the solstices. My house had a good view of the horizon of both rising and setting sun, and, yes, I applied a correction for refraction, as if that mattered.
Also - for the record - in the approximation where the solar declination doesn't change over the course of 24 hours, the equation is:
Lat = arctan( (cos (d/2))/tan(decl))
Where d = length of day in degrees or radians. It obviously breaks down when decl=0. Try remember this and calculate this on a life raft.
John H.
--~--~---------~--~----~------------~-------~--~----~
NavList message boards: www.fer3.com/arc
Or post by email to: NavList@fer3.com
To , email NavList+@fer3.com
-~----------~----~----~----~------~----~------~--~---