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    Re: Celestaire vs Freiberger Yacht Sextant
    From: George Huxtable
    Date: 2004 Aug 2, 10:40 +0100

     Joel Jacobs  wrote:
    
    
    >From my experience, if your going to do serious navigation relying on
    > twilight sights, the 7/8 scale sextants are very lacking. Their optics are
    > not very good, and there small size mirrors are not anywhere as effective
    > when taking star sights or high altitude sun sights.
    ===============
    
    Something about that puzzles me. Why should it be so, I ask?
    
    First, I should make it clear that I have never even handled such a 7/8
    size sextant; and that observations on my own small boat have never passed
    beyond a plastic job, though I have used many "posh" sextants, belonging to
    others. So I make no claims to being an expert on sextants.
    
    Yet, it seems to me that if you were to shrink a sextant to 7/8 of its
    original size, and shrink its mirrors correspondingly (in both directions)
    while preserving the same angular field-of-view of its telescope, then
    (because the distance from the eye to those mirrors is also reduced to 7/8)
    the patch of sky that the mirrors subtend would be exactly the same as
    before.
    
    So, in those circumstances, why should the smaller mirrors present any
    disadvantage?
    
    George.
    
    ================================================================
    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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