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    Re: Sextant precision
    From: George Huxtable
    Date: 2004 Sep 30, 12:46 +0100

    This is a response to  Alex Eremenko-
    >On Wed, 29 Sep 2004, George Huxtable wrote:
    >> Alex Eremenko asked about the precision of
    >> sextants and sextant measurements.
    >> This is a matter which surfaces from time to time on Nav-L,
    >I think I read all previous discussions related to sextants,
    >all I could find using the search engine.
    Try the threads starting about 16 March 03, with headings such as "sextant
    accuracies", and "sextant accuracy and anomalous dip", though these veered
    off into other territory without changing threadname. You may find other
    discussions if you search for threads which include the word "accuracy".
    I had written-
    >> And yet, on this list, the finer points of calibration
    >> of these expensive
    >> and exotic instruments, ancient and modern,
    >> are discussed in detail,
    >You are not objecting this, do you?
    No, not at all, but I suspect that for many, all those instruments will be
    used for is for altitudes, in which such exactness is rather wasted (though
    it does no harm, of course!).
    For anyone intending to measure lunar distances (which includes Alex), he
    needs all the precision he can get, and that's why I said that in that case
    he is asking the right questions.
    What I was trying to do was to take some of the magic and mystery out of
    the sextant when used as a tool to measure altitudes from a small vessel,
    for which it is vastly over-qualified.
    >> There's another list which is devoted to sextants
    >Could you please give me the address?
    Below is a copy of a message of a few years back from Will O'Neil, who
    looks after the "sextants" list. He's an occasional contributor to Nav-L
    You will find much less traffic than on Nav-L, and it's less concerned with
    technical matters, and more with questions of genuineness or fakery,
    purchasing, identification, maker's marks and numbers. So it perhaps
    appeals more to the collectors, in my view. It's worth being a member of
    both Nav-L and the sextants list, as are many of us.
    I'm sure Will will assist any prospective joiner to sign up.
    From: "Will O'Neil" 
    Subject:      Hi & "the other list"
    Just joined the list. I did a lot of star sights as USN navigator in 1960s
    (and a few more thereafter until sextants pretty much disappeared from USN
    bridges). Presently an amateur student of history of navigation and
    navigating instruments, and collector of old instruments.
    I'm also the moderator of another list (or group) in a subject area closely
    related to that of navigation-l. This is the group Sextants hosted on
    Yahoo! Groups. (Nothing to do with Yahoo! -- they just provide place for
    such things.)
    The group isn't restricted to sextants; it also deals other instruments for
    measuring visual dihedral angles at sea, aloft, or in the field; the use of
    such instruments for navigation, surveying, and like purposes; and other
    related matters including marine and air navigation, surveying, and the
    industry and technology that produced these instruments. Everyone is
    welcome to post information and questions regarding history, specific
    instruments, sales, wants, etc.
    Naturally, there's a certain overlap in subject matter with navigation-l.
    Sextants runs a bit more to history, however.
    One reason I set it up as a Yahoo! group in the first place is that it
    allows storage of archival material, including documents, images, etc.
    Sextants has e-copies of a number of important articles on sextant history,
    a bibliography of materials relating to sextants, and pix of some
    instruments owned by members.
    Membership is open (and it's easy to unsubscribe if you decide it's not for
    you). Most people use the Web interface, at
    You can also treat it like a list. Send message to
    There are about 100 members and the traffic volume isn't going to overwhelm
    anyone, I'm pretty sure.
    If you are not already registered with Yahoo! Groups for some other
    purpose, you will be asked to sign up. They will want some information, of
    which only your e-mail address actually has to be correct. There is no
    other way to get access to this group except via Yahoo! Groups.
    If you have any questions, just send me an e-mail: will.oneil{at}pobox.com.
    I'll do my best to answer. Some people have had difficulties in getting the
    Yahoo! Groups software to accept their subscriptions -- let me know if this
    happens to you and I'll try to "force" your subscription through.
    Will O'Neil
    contact George Huxtable by email at george---.u-net.com, by phone at
    01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy
    Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.

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