NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Plastic sextants. was: GPS shortcomings.
From: Frank Reed CT
Date: 2005 Jun 11, 03:09 EDT
From: Frank Reed CT
Date: 2005 Jun 11, 03:09 EDT
George H you wrote: "Dave makes a fair point, but as I see it, it would apply only to observations where a significant fraction of the length of the sight-path to the horizon is over the land (or sandy shore, or drying reefs, whatever). Otherwise, the surface temperature, even in shallow water, would not differ all that much from the open sea, except in some very-odd environments." There's more to it than that. You can get more complicated layering of air layers with different temperatures close to shore. Near Mystic, Connecticut in the spring and fall, it's not that uncommon to see five or more arcminutes of anomalous dip, and this is for sights taken on water (but within sight of land). -FER 42.0N 87.7W, or 41.4N 72.1W. www.HistoricalAtlas.com/lunars
