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    Re: Jupiter's moons
    From: Herbert Prinz
    Date: 2002 Mar 21, 00:51 +0000

    Nigel,
    
    I believe this is a misunderstanding. Sighting pieces differ mainly in
    magnification, field of view and light power or whether the image was erect or
    inverted depending on whether they were optimized for observing the Sun or the
    stars, on a steady deck or in a seaway, or for altitudes or distances. None
    were suitable for Jupiter satellite observation. Why would one want to observe
    satellite phenomena with a sextant, anyway? It's difficult enough with a
    suitable telescope. Try to watch (never mind timing!) Jupiter's satellites with
    your regular binoculars, and you will see what I mean. Sighting pieces are and
    were certainly not better than modern binoculars.
    
    By the way, does Riddle really say "occultations" ? He sure means "eclipses",
    doesn't he?
    
    
    Nigel_Gardner wrote:
    
    > Herbert wrote  magnification do/did
    > these sighting pieces have?>
    >
    > I am afraid I have not, in UK decent old sextants have been priced out of
    > navigators' markets by being bought up by chi-chi antique dealers to sell
    > to people to hang on a wall.  My own 'good' sextant is a modern Zeiss but
    > with only one eyepiece.
    > I looked in my copies of Nories Epitome (one 1805 and the other 1896) which
    > give good, long and lucid descriptions of sextants. Both descriptions say
    > that a sextant is normally equipped with two magnifying eyepieces of
    > different strengths but neither sadly give any indication of what the
    > stengths are.
    >
    > NG
    
    
    

       
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