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    Re: Mid XIX century Nav
    From: Fred Hebard
    Date: 2005 Nov 14, 22:34 -0500

    The cable guys were using an artificial horizon to do the time
    sights.  I expect it's more precise.  First, they could mount the
    sextant on a tripod.  Second, the altitude is half the sextant
    reading, doubling the precision.  Third, could use the 12x inverting
    scope.  Don't know whether there are additional advantages; they also
    _may_ have used a pendulum clock so the observer could time the
    conjunctions .  Chauvenet and Wharton & Fields may discuss these
    advantages.
    
    Fred
    ------------------------------------------------------------------------
    Frederick V. Hebard, PhD                      Email: mailto:Fred{at}acf.org
    Staff Pathologist, Meadowview Research Farms  Web: http://www.acf.org
    American Chestnut Foundation                  Phone: (276) 944-4631
    14005 Glenbrook Ave.                          Fax: (276) 944-0934
    Meadowview, VA 24361
    
    
    On Nov 14, 2005, at 10:19 PM, Alexandre E Eremenko wrote:
    
    > Meridian observations
    > (with a meridian circle or teodolite)
    > need a firm base. But what about time
    > sights?
    >
    > Alex.
    >
    > On Mon, 14 Nov 2005, Fred Hebard wrote:
    >
    >> Alex,
    >>
    >> I would expect they wanted to do some time sights to rate the
    >> chronometers.  In addition, (although I'm less sure on this) they may
    >> have done some transits to find absolute time.
    >>
    >> There's a great account of repairing cables in the late 19th century
    >> where the fellows go ashore to rate their chronometers.  I can't
    >> recall the name nor find the book, but it was mentioned here a few
    >> years ago.
    >>
    >> Fred
    >>
    >> On Nov 14, 2005, at 7:36 PM, Alexandre E Eremenko wrote:
    >>
    >>> I am reading a book by a famous Russian XiX century
    >>> author, Goncharov, on his voyage to Japan in 1853/4.
    >>>
    >>> (The Russians were trying to "open" Japan for trade
    >>> at that time, the same thing did the Americans (at exactly the same
    >>> time).
    >>> Japan was "closed to foreigners"; no one could land
    >>> etc. I don't want to describe all details.
    >>> Anyway, the Russians were negotiating with the Japanese
    >>> authorities for a permission to land. The following episode
    >>> in this long and complicated negotiation, which lasted several
    >>> months, attracted my attention. The Russians asked for a
    >>> permission to land on some rock between their ship place
    >>> and the land. Apparently a small uninhabited island.
    >>> The reason they clamed for this permission was the
    >>> "Necessity to check chronometers".
    >>> Apparently they thought that this was a good reason
    >>> for landing on a rock).
    >>>
    >>> Unfortunately the author of the book was not interested
    >>> in navigation and did not want to explain to the readers
    >>> this point. WHY did the Russians think that this was a
    >>> legitimate reason?
    >>>
    >>> Why exactly did they need land to check their chronometers?
    >>> Or, more precisely, why did they think that "checking chronometers"
    >>> is a legitimate reason for a landing?
    >>>
    >>> What was the proper procedure of "checking chronometers" they had
    >>> in mind?
    >>> Was this by the Lunars?
    >>> Did they mean that a firm ground
    >>> is needed for the Lunars? Or Jupiter satellites? to install a
    >>> powerful
    >>> telescope?
    >>>
    >>> (They were at ancor in the Nagasaki harbor at that time. Nagasaki
    >>> was one of the few cities where foreigners were permitted to stay
    >>> on ancor
    >>> at that time). To finish this part of the story I just say that
    >>> they were
    >>> not permitted. The Japanese quickly built some structure on the
    >>> rock,
    >>> as an evidence that this rock was "land", rather than some "rock in
    >>> the
    >>> sea"
    >>> or "uninhabited (and unclaimed?) island" where anyone can land.
    >>> Before
    >>> arriving
    >>> to Nagasaki, the Russians signed the paper that they will not land
    >>> without
    >>> the permission of the authorities.)
    >>>
    >>> But I only wanted to discuss the CelNav part of the story.
    >>> Why did the Russians think that "checking chronometers" was a
    >>> legitimate
    >>> purpose of landing on a rock?
    >>>
    >>> Alex.
    >>>
    >>> P.S. I am well aware that the first underwater transoceanic cable
    >>> layings
    >>> were made at about the same time. So the Lunars were doomed,
    >>> already then,
    >>> even as a
    >>> mean
    >>> of checking chronometers:-(
    >>
    
    
    

       
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