NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Why is a sextant like it is?
From: Trevor Kenchington
Date: 2004 Nov 17, 20:38 -0400
From: Trevor Kenchington
Date: 2004 Nov 17, 20:38 -0400
George, Interesting question. I'll take a guess that the common layout of the sextant was based on that of Hadley's quadrant, which itself was primarily intended for Sun sights, for which the convenience of looking horizontally outweighs other considerations. If so, your question could be re-phrased as: Why did the form of sextants not evolve to make them easier to handle for lunars and for star sights? The star sights may be easily answered: If most mariners pre-computed their twilight sights, inverting the sextant to find a particular star will have been too unusual to merit a major re-design of the instrument. That leaves lunars, for which I have no such simplistic answer. Reading the on-running threads amongst the "lunartics" on this list, I am often left trying to visualize navigators, at sea under sail, contorting themselves in an effort to get highly-precise measurements of distances between awkwardly-placed celestial bodies, half-obscured by sails and rigging and I just can't picture that. I would expect that memoirs of the time would mention the awkward observations but I am not aware of any that do. Is it possible that the rare lunar observations (and we know they were rare) were normally only made when the required distance could be measured _without_ awkwardness? Trevor Kenchington -- Trevor J. Kenchington PhD Gadus@iStar.ca Gadus Associates, Office(902) 889-9250 R.R.#1, Musquodoboit Harbour, Fax (902) 889-9251 Nova Scotia B0J 2L0, CANADA Home (902) 889-3555 Science Serving the Fisheries http://home.istar.ca/~gadus