NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Mid XIX century Nav
From: George Huxtable
Date: 2005 Nov 23, 15:40 -0000
From: George Huxtable
Date: 2005 Nov 23, 15:40 -0000
Frank Reed had written- If we don't trust the tabulated longitude, you have other options for determining longitude ashore like moon culminations that are generally more accurate than lunars. These depend on a careful determination of true azimuth. to which I had objected > "But I'm not so convinced about the practicality, for a ship's navigator, > of > timing Moon culminations" And Frank now says- > I agree. I wouldn't expect any ordinary navigator in the 19th century to > do > anything like this. Rather, I would expect a typical navigator with a > chronometer to test it by ordinary time sights from the first port with a > trusted > longitude, perhaps supplemented by occasional lunars while in regions > with > uncertain longitudes. But, if this was putatively a voyage of > "exploration" (as > it seems to have been, at least in theory), then I would expect you might > have > an observer with greater astronomical skill. It seems we agree, then, that a ship's navigator would not be determining his time that way, although we disagree about why. Frank presumes that a ship's navigator would not have the skill to do so, which may well be the case. However, even if he had that skill, he would not have had any instruments to allow him to make the "careful determination of the azimuth" that would be necessary. An astronomer or surveyor may have carried such instruments, but not a ship's navigator. George. contact George Huxtable at george@huxtable.u-net.com or at +44 1865 820222 (from UK, 01865 820222) or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.