NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: {Spam?} Sobel and Longitude. was:: Re: David Thomson and his lunar tables
From: John Huth
Date: 2010 Mar 19, 13:33 -0400
From: John Huth
Date: 2010 Mar 19, 13:33 -0400
Perhaps the definition of a conscientious navigator is one who would take a lunar when the opportunity arose?
I'm trying to track some pre-1500 material on lunars. There's a paper by John Kirtland Wright who found some sources as far back as the middle ages where the authors speculate on what are effectively lunars - I can give you the source. Then, there are the accounts of Columbus using lunar eclipses to try to measure longitudes - the most famous being the St. Ann's Bay episode.
In that era, I think the best one could do would be a crude timing of eclipses using hour glasses and extract a time relative to sunrise/sunset or some other easy event. If there's any material on pre 1500 mentions of lunars, I'd be grateful to hear it. I only have the Wright article and the Columbus stories (via Samuel Eliot Morrison's biography).
On Fri, Mar 19, 2010 at 11:40 AM, Ken Muldrew <kmuldrew@ucalgary.ca> wrote:
On 18 Mar 2010 at 23:38, George Huxtable wrote:
> But in the
> lunar era, a conscientious navigator would take a lunar when
> the opportunity arose, when the Moon was visible in a clear sky. It was
> part of the "professional pride" that Henry has referred to.
George,
Do you have any historical evidence to support this claim? Although
instructors of navigation may have wished for such zeal in their students,
without historical evidence, such as logbooks, one should be skeptical.
The logbooks that Frank has studied, and written about here, provide a
different view of how navigators depended on lunars in that era. It may be
that his sources (primarily American whalers) have a bias toward a certain
type of navigator, but anyone proposing that hypothesis is obligated to
provide some evidence to support it. Frank's historical evidence from
primary sources has to be considered a trump card in this debate until
such time as other sources can be shown to contradict, or at least temper,
his conclusions.
Ken Muldrew.
