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    Re: Night Vision Scopes
    From: Alexandre Eremenko
    Date: 2005 Jun 27, 12:39 -0500

    I have never used a night vision device,
    but on a pure theoretical ground I predict
    that it will NOT help to see the sea horizon:-)
    (And for the stars and the Moon you don't need
    any night vision anyway).
    Can anyone verify this theoretical prediction?
    P.S. I mean the common modern night vision devices based on infrared
    radiation. Another tipe of "night vision scope" was invented
    in XVIII century, and this was simply a Galileo scope
    with small magnification and with large
    object lens diameter. (Approximately of the same type as
    the standard straight non prismatic scopes of modern sextants).
    These scopes indeed help with horizon or any other object at
    night simply because they collect more light.
    On Sat, 25 Jun 2005, george huxtable wrote:
    > Robert Eno wrote-
    > >Has anyone used a night vision scope for conducting star sights at
    > >sea?  The idea intrigues me and in theory it sounds like it would work,
    > >but I do not know anyone who has actually used one at sea.
    > An interesting question. Presumably you would use it in place of the
    > telescope, to show up both star and horizon. Otherwise, how well would the
    > sight-line of such a night scope be defined? And how would you check for
    > index error?. I only ask, because I am quite unfamiliar with such instruments.
    > Could a digital camera be used for the same purpose? Amateur astronomers
    > use quite ordinary arrays for looking at stars.
    > I think one of the difficulties would be the fast motion of the images with
    > respect to the screen as the vessel wobbled underfoot. The human eye is
    > good at assessing the relative positioning of star and horizon, even while
    > they are whistling across his field of view. An electronic screen could
    > find that job to be more difficult. Perhaps some image stabilisation would
    > be needed also.
    > But a sextant with lots of electronics attached: wouldn't that be getting
    > the worst of both worlds? The most satisfying aspects of a sextant are its
    > precision and its basic SIMPLICITY.
    > George.
    > ===============================================================
    > Contact George at george@huxtable.u-net.com ,or by phone +44 1865 820222,
    > or from within UK 01865 820222.
    > Or by post- George Huxtable, 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13
    > 5HX, UK.

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