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    Re: Children's land-locked "Sextant"
    From: Robert Eno
    Date: 2007 Nov 29, 09:28 -0500

    Alexandre,
    
    I've been using mine for years with no ill effects.
    
    Putting it on a wood table is not the way to go. In fact, aside from a moving 
    train or the heaving deck of ship, it is probably worst platform on which to 
    situate this type of artificial horizon. It is therefore not suprising that 
    the results were dissapointing. The instrument should be mounted on a solid 
    surface. Concrete or rock is the best.
    
    As for accuracy, I have been able to fix my position to within tenths of a 
    nautical mile using this and my Plath sextant. Good enough for my purposes. I 
    don't know what your intended application is, however, if you require even 
    more accuracy than this, you need a theodolite.
    
    I don't see you being any further ahead with mercury as it too, would be 
    subject the same disturbances and I have already provided my opinion on the 
    health hazards associated with mercury vs. the advantages of having a 
    self-levelling artificial horizon.
    
    I like the idea of an artifical horizon made with a cast iron frame, however, 
    I doubt if we will ever see it in mass production. There is not likely much 
    of a market for such an item outside of our group.
    
    Robert
    
    
    ----- Original Message -----
    From: Alexandre E Eremenko 
    Date: Wednesday, November 28, 2007 11:34 pm
    Subject: [NavList 4159] Re: Children's land-locked "Sextant"
    
    >
    >
    > On Wed, 28 Nov 2007, Robert Eno wrote:
    >
    > > Consider a black glass artificial horizon. Frieberger
    >
    > I've seen one of those and tested it in Freiberger's
    > office (in Freiberg, Germany).
    > The price was something like 900 Euro, but they were very
    > nice to me and offered for only 700 (if I pay cash on
    > the spot:-)
    > To try, we put it on the wood table in their office
    > (on the second floor of a brick building in a quiet
    > street in a small quiet city) I asked everyone to sit
    > down and stop breathing for a while. And aimed my sextant
    > at the Sun reflection (SNO-T, 6x scope). It was shaking
    > like crazy (5-10 minutes amplitude by eye estimate).
    >
    > So I decided not to spend 700 Euro for a piece of glass
    > in a drame with 3 screws and a pair of levels.
    >
    > Actually I believe that a handyman with simple tools can
    > make such thing himself. Optical quality glass seems to
    > be available on the Internet for a reasonable price.
    >
    > Besides, 30" ADVERTISED accuracy did not seem sufficient
    > for the sort of observations I am doing.
    >
    > Alex.
    >
    > P.S. I don't know whether Ken is reading this (have seen no
    > posting from him for long time)
    > but I suggest that Celestaire could make an art horizon of
    > heavy iron, perhaps it will shake less
    > (the real ones were made of iron for
    > another reason: iron does not amalgamate witrh Mercury,
    > unlike other metals). Only once I've seen an old iron
    > artificial horizon on e-bay, complete, with iron mercury
    > bottle). It was sold for $800 about a year ago.
    >
    >
    >
    >
    > >
    >
    
    
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