NavList:
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Star lunars. was: Sobel and Longitude
From: George Huxtable
Date: 2010 Mar 19, 21:19 -0000
From: George Huxtable
Date: 2010 Mar 19, 21:19 -0000
Ken has asked a very fair question, and I'll do what I can to answer his challenge. But first, let me be clear that I'm not claiming that navigators' logs will show a preponderance of star-Moon observations. Most will be of Sun lunars, because that's the easier option. What I'm claiming is that, at times when a lunar was desirable, and a Sun lunar was unavailable, mariners were expected to be able to use a star; and did so. Unfortunately, the two sets of ship's-logs, that I have recently studied in detail, don't help. One was of an arctic whaler who only ever took Sun lunars, because no stars were ever visible in his Arctic summer whaling seasons. The other was of Cook's transatlantic crossings over 1764 to 1767. Although the new Nautical Almanac appeared in the last year of those voyages, making lunars practicable for the ordinary mariner, Cook had not then learned to use them. It was not until 1768, on his first circumnavigation in Endeavour, that he learned the art from the astronomer Green. So I took a look in the Beaglehole account of that voyage, which started from Plymouth on 23 August 1768.. I will list the body used with the Moon, when a lunar was recorded, on the first leg of the journey as far as Rio de Janiero.. 5 September. Sun 6 Sun 4 Oct. Sun 15 Sun 16 Sun 17 Sun 20 Sun 21 Sun 28 Arietis, Pollux 2 Nov Aldebaran, Sun 3 Sun 4 Sun 14 Arrived Rio Perhaps Ken might object that these were atypical, being of a famous navigator (though not so famous then) in a well-found research vessel, in the process of being trained up by a professional astronomer. Which, if he did, I couldn't deny. What we really need to compare is the log from a more ordinary trading voyage, such as one of the thousands made by the East India company somewhere round 1800. I don't have any such at hand, but will see what I can find. George. contact George Huxtable, at george@hux.me.uk or at +44 1865 820222 (from UK, 01865 820222) or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. ----- Original Message ----- From: "Ken Muldrew"To: Sent: Friday, March 19, 2010 3:40 PM Subject: [NavList] Re: {Spam?} Sobel and Longitude. was:: Re: David Thomson and his lunar tables | 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. | | |