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    Re: Sextant development:was Re: Sextants in Little Rock
    From: Henry Halboth
    Date: 2010 Jan 9, 12:56 -0800
    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.

    --- On Sat, 1/9/10, George Huxtable <george@hux.me.uk> wrote:

    From: George Huxtable <george@hux.me.uk>
    Subject: [NavList] Sextant development:was Re: Sextants in Little Rock
    To: NavList@fer3.com
    Date: Saturday, January 9, 2010, 5:35 AM

    Henry (hch) raises several interesting points about sextant development.

    I wasn't aware that during the earlier years of World War 2, drum  sextants
    were so hard to get, outside the military, in the US. How long before that
    did drum sextant manufature in the US start, then, and by which firm(s)?

    We can imagine why supplies were so short. Each new vessel would be
    replacing another that had been sunk by a U-boat, and gone down, most
    likely, with its navigators and their sextants.

    When he bought his Husun sextant in Glasgow during the war, was that a new
    instrument? I wonder if the sale of such sextants was then restricted, and
    whether Henry had to show any documents to buy it? Perhaps, in those days,
    his American accent was enough... It would be quite a feat of memory to
    recall such details, from 60-odd years back; unfair to ask, perhaps.

    And it's interesting to learn that after experience with both Vernier and
    drum instruments, Henry settled on a Vernier Plath, because of its superior
    optics. That, it seems, was more important to him than the easier-reading of
    the modern drum. The main trouble with a Vernier instrument, it seems to me
    (after very limited practical experience), is the difficulty in getting
    precise readings from the Vernier scale for twilight observations,
    particularly in poor lighting. Would there always be electric lighting
    available on the bridge in Henry's early days, or were some oil lamps still
    in use? I can remember a passage on a steam coaster, from Liverpool to
    Belgium, around 1950, in which all lighting was still by oil lamps. I am
    aware that bright lighting is to be avoided, to preserve night vision, but I
    wouldn't relish reading a Vernier under oil-light, even in the days when my
    eyes were much sharper than they are now.

    I remain puzzled by one aspect of the transition from Vernier to drum
    sextants. The first Plath drum instruments were in their catalogue from
    1907. However, they didn't appear in the catalogues of Heath, or Hughes,
    until the late 1920s. Even if the Germans were ahead with their machine
    tools, I find it hard to explain the 20-year gap.Even if Plath had the
    patents sewn up, patents don't last that long, and German patent rights were
    unlikely to be given much respect during a World War. Were the new-fangled,
    foreign, drum instruments distrusted by non-German mariners? Was there any
    basis for such distrust? Were they eagerly accepted by German navigators?
    Did those early Plath drum instruments achieve the same precision as their
    Vernier counterparts? I wonder if opinions, around that time of the 1910s,
    can be found in pages of the nautical journals.

    Once Heath had introduced the "endless tangent screw" to their Vernier
    sextants, it might be imagined that they were most of way towards the drum
    sextant. All they had to do next, it seems, was to replace the simple knob
    by a graduated drum, and make the screw-pitch correspond to exactly 1 degree
    on the scale. That last requirement , however, called for extreme precision
    of both rack and worm. Was Heath's technology simply not up to the job?


    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: "hch" <h.halboth@yahoo.com>
    To: <NavList@fer3.com>
    Sent: Saturday, January 09, 2010 3:26 AM
    Subject: [NavList] Re: Sextants in Little Rock

    Hi Frank,

    I believe it safe to say that by the mid-1940s transition
    from vernier to micrometer drum sextants was well underway, if not actually
    completed. It as just that the micrometer drum sextants were not generally
    commercially available in the USA – certainly the military, both Allied and
    Axis, had them and they were being issued to new built merchant ships by the
    Maritime Administration, but over the counter sales were non-existent or, at
    least, very limited, thereby extending the life and availability of older
    vernier sextants which could still be found on the 2nd hand market
    The opposite situation prevailed in Great Britain where you could walk in
    by a Husun “three ring” micrometer sextant over the counter most anytime
    1943, or thereabouts – IMHO this latter simple sextant contributed
    to the winning of the Battle of The Atlantic, and most Allied Seamen that I
    knew aspired to owning one.

    Micrometer sextants apparently were around, although not
    plentiful, since at least the 1920s, facilitated by the incorporation of the
    rack and pinion drive arrangement for movement of the index arm – I
    have never seen such an instrument without this drive arrangement, which was
    also incorporated into the vernier type sextant by Plath in later years,
    doing away entirely with the old style index arm clamp and friction fine
    adjustment arrangement in which the tangent screw could come “two blocks”.

    My first “sextant” was actually a John Bliss & Co.
    octant, purchased second hand (more likely third to fifth hand) at their
    establishment on Pearl Street in New York City in late 1943 – it was then
    probably in the order of 60 to 80 years old, had the old style index arm
    and limited run friction fine adjustment device for a 15 second vernier, and
    was encrusted with a dark green coating of verdigris, making it a real
    old dog”. Well sir, this old dog navigated me over a good part of the world
    competed favorably in every day sights, including stars, with any modern
    sextant it came up against; it stared my lifelong affinity fort vernier
    sextants – I still have it today.

    Subsequently, I did join the crowd. While lying on the hook
    in the convoy anchorage off Gourock, Scotland, I got enough time off to
    the AM train to Glasgow, where the Winfred O. White establishment was
    directly across from the Station, purchase a Husun “three ring” sextant for
    about $60.00, and return to my ship by way of the PM train. I have since
    and used German, Japanese, and British micrometer sextants of every
    description, but finally settled on a relatively simple Plath, certificated
    1946, fitted with a 10 second double spaced vernier, and endless tangent
    i.e., rack and pinion drive. My preference for the Plath resides primarily
    in the
    telescope, which I simply find to be personally more comfortable in use.

    Sorry to offend those who don’t like sea stories, but you
    did ask.



    --- On Fri, 1/8/10, FrankReed@HistoricalAtlas.com
    <FrankReed@HistoricalAtlas.com> wrote:

    From: FrankReed@HistoricalAtlas.com <FrankReed@HistoricalAtlas.com>
    Subject: [NavList] Re: Sextants in Little Rock
    To: NavList@fer3.com
    Date: Friday, January 8, 2010, 11:27 AM

    Henry, you wrote:
    "The term "endless tangent screw sextant" was a common expression for the
    sextant sub-type possessing such a device, prior to the common usage of the
    endless or geared tangent screw - it it recognized as a sextant sub-type by
    definition in HO 220."So then, circa 1940-45, it still would have been "new
    enough" that a sextant would specifically have been referred to as "endless
    tangent screw" as a novelty? Was your first sextant a micrometer sextant?
    And was this distinct from an "endless tangent screw" sextant? Or were all
    micrometer sextants also "endless tangent screw" sextants?You added:
    "The abbreviation ETS is not, however, a recognized or, at least, defined
    abbreviation except in the imagination of the originator. Today, folks seem
    to make up abbreviations as they go along and everybody else is expected to
    understand - apparently a requirement of the electronic age. "This bugs the
    hell out of me, too. It's the era of acronyms. Linguists say it started
    around 1925. Before then, you will almost never find acronyms (famously,
    this is one of the reasons why you can be sure that "POSH" was not an
    abbreviation for "port out, starboard home" as in the popular 'folk
    etymology'). Acronyms are now everywhere. But it's not going to change, so I
    guess we better "learn to love and live with acronyms" -- a policy which I
    call "LLLWA" or in print "L3WA" (so there's no misunderstanding... I am
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