NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Sextant development:was Re: Sextants in Little Rock
From: Henry Halboth
Date: 2010 Jan 9, 12:56 -0800
From: Henry Halboth
Date: 2010 Jan 9, 12:56 -0800
George,
By golly, young fella, you do know how to ask the questions - no offense intended - and I will make the effort to answer those that I possibly can.
Yes, the Huson I bought in Glasgow was brand new and, while I may have been asked to show some form of identification in making the purchase, there were no formalities, permissions, or otherwise, required. It was a straightforward cash and carry deal.
Yes, reading off a vernier sextant can require more and better placed illumination than that required for a micrometer sextant, however, both do require light and thereby some compromise of night vision. Most micrometer sextants have a built in lighting system, while most vernier sextants do not, although I have seen some advertised as having such a system installed, however, have never actually seen such an instrument.
Yes, reading off a micrometer is faster than reading off a vernier - if I were to hazard a guess, perhaps in the order of 10-seconds faster, per observation. And, no there should be no significant difference in the accuracy of the read-off, assuming, of course, that the micrometer is fitted with a vernier equally divided as that of the vernier of the vernier sextant.
I really don't know what others do, but over the years I have developed a method of reading a vernier which, I believe, gives the greatest possible accuracy of result - that is to read into the linear coincidence from both sides, noting the progressive decrease in linear separation
until a consensus of coincidence is arrived at from both sides. This may sound more complicated than it is and takes but a few seconds longer than just a quick look.
While on the subject, I am a believer in "singular responsibility" for an observation - meaning simply that I take the full responsibility for all aspects of the sight, i.e., altitude observation, time (chronometer) read off, all aspects of reduction, and plotting. I will have nothing to do with the "committee approach" wherein one person takes the altitude, another reads the time on being given a "mark", and several others work out the various reduction components, and call them out to the one actually doing the reduction - aboard one Navy ship on which I served, this was done, and the chartroom sounded like an auction center while a sight was being worked; can you just imagine the "hurrahs nest" that ensued in trying to place the blame in the event of a mistake. Needless to say, this all came to an abrupt end when I became N-Division Officer and took over navigational responsibilities - but that is another sea story, all by itself. All I
will say is, that in my time, the Navigator did, and was fully responsible for, ALL the navigaton, assisted by the QMs as he directed them.
The onset of WWII found the US sorely lacking in the manufacture of nautical instruments, and that included Sextants and Chronometers. The development of the Hamilton Chronometer is an epic of clockmaking ability which resulted in an exceptionally fine instrument outside the realm of this posting. The capabilities of Lionel, Bendix, Shick, and others were pressed into service to develop or increase the production and availability of sextants, and these organizations responded admirably to the need presented, however, as far as I know their production went primarily to the Government, and few if any of these instruments found there way into the commercial market - at least during the war years. I will not criticize these American produced instruments, however, will say that they did not find immediate acceptance by MM Officers - to these men the American instruments looked strange; they did not have the heft and appearance of the traditional
British sextants to which they had become accustomed over the years, and they didn't even look like the pictures they had seen in their textbooks; in a word, they shunned them like the pox and sought out the more traditional looking instruments, such as the Husun three ringer. Unjust, but true.
I am sure that others are far more capable than I to discuss the development of the micrometer sextant and will defer to their expertise in this area of your questioning.
Regards,
Henry
--- On Sat, 1/9/10, George Huxtable <george@hux.me.uk> wrote:
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