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    Re: Artificial horizon: firm base needed.[was Your Mail]
    From: Jan Kalivoda
    Date: 2004 Sep 30, 17:43 +0200

    Yes, Alexandre's hypothesis about artificial horizons on icebreakers can be 
    true. I have the copy of the Russian book titled "How to determine ship's 
    position by the Sun and to judge its accuracy" in translation, written by 
    V.F.Dyakonov from the year 1954 and printed in Leningrad = Sankt-Peterburg. 
    An extremely good text, at the outset discussing all aspects of Sun 
    observations over the natural and the artificial horizon and of computing the 
    Sumner lines. But the core of the book is the effort to find a procedure for 
    obtaining the astronomical positions during the polar day, when only the Sun 
    was available for navigators on icebreakers, the natural horizon was mostly 
    unclear and it was not possible to make the classical running fixes while 
    sailing through ice fields - the DR was almost unusable due many alterations 
    of the course and due the absolutely inaccurate idea of the distances sailed 
    (because of the resistance of ice and the unavailability of most types of 
    logs in the!
     ice).
    
    His conclusion (proved by the analysis) was that it is possible to stop the 
    icebreaker or any ship while running through the ice, to turn off the 
    machines for eliminating the most disturbing vibrations, to take two Sun's 
    altitudes cca 15 minutes apart over the artificial horizon and to reduce them 
    by the method similar to Ageton's one a bit and using the 5-figures logs of 
    tangents (tables for this method were available as an adjunct in the official 
    Soviet collection of the navigational tables at that time). There are not 
    significant waves in ice fields, so that the artificial horizon is 
    purportedly (the author says) usable in such situation. Thanks to the 
    artificial horizon and the log tangents (and the high polar latitudes, where 
    heavenly bodies move nearly horizontally in their daily motion), the result 
    was as accurate as the fix from two LOP's differing by 30 - 40  degs in 
    azimuth, measured over the natural horizon and computed by 4-figures logs of 
    sines and Gauss logs (t!
    he standard method for reducing sights in the Soviet Navy then, as the 
    haversines weren't used there) in temperate latitudes, according to the 
    author. And maybe the Alexandre's assistent holding the artificial horizon in 
    hands could be useful - the ship isn't an absolutely stable platform even on 
    the calm sea surface among ice floes and with the main machine stopped.
    
    
    Jan Kalivoda
    
    
    
    ----- Original Message -----
    From: "Alexandre Eremenko" 
    To: 
    Sent: Thursday, September 30, 2004 3:57 PM
    Subject: Re: Artificial horizon: firm base needed.[was Your Mail]
    
    
    > On Thu, 30 Sep 2004, George Huxtable wrote:
    >
    > > Alex wrote-
    > > The Russian manual says about "a plate with machine oil
    > > which an assistant holds in his hands".
    > > The assistant is probably needed
    > > to absorb the vibration of the ship's engine!
    > >
    > > Tell us more, please, Alex.
    > > I find it hard to believe that any assistant
    > > could have steady enough hands to hold a liquid horizon
    >
    > The sentence inside the quotation marks is what the manual says.
    > (The next sentence was my own speculation.)
    > The passage in the manual on the artificial horiaon begins with
    > "If the horizon is not visible, altitudes can be taken with
    > artificial horizon..."
    > The manual I refer to is a little book in Russian:
    >
    > by Kondrashikhin and Rakhovetskii,
    > "Astronomical determinations of the ship position and of
    > the compass correction"
    >
    > which I bought in 1967 and read
    > so carefully that I can cite it by heart even now.
    > Unfortunately the book was lost when I was moving to the US.
    >
    > But I am confident that I cite the passages from it correctly.
    >
    > > I havent come across an
    > > account of any successful measurement made with an
    > > artificial horizon on
    > > board a ship at sea.
    >
    > Nest time I travel on a ferry and have my sextant with me
    > I will try.
    >
    > > If
    > > that was a standard Russian procedure, it would be
    > > interesting to learn about it.
    >
    > I don't see how to verify this at this moment. It is possible
    > that the procedure was intended for observations from the ice,
    > on icebreakers. I definitely remember reading (in another
    > book)
    > that such observations from the ice were routine. Even remember
    > seeing pictures...
    >
    > Alex.
    >
    >
    >
    > --
    > Incoming mail is certified Virus Free.
    > Checked by AVG Anti-Virus (http://www.grisoft.com).
    > Version: 7.0.271 / Virus Database: 264.9.8 - Release Date: 28.9.2004
    >
    >
    
    
    

       
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