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    Re: How does the AstraIIIb split mirror work?
    From: Robert Eno
    Date: 2004 Apr 26, 16:31 +0100

    I have been following this discussion off and on and confess that I have
    not been paying it close enough attention. With that in mind, perhaps one
    of our more erudite members (do you hear me George?) can provide a
    summary of the supposition, observations and conclusions that have
    transpired over the past few weeks.
    I'd like to add here that I am not a big fan of the split horizon, which
    has been the subject of much discussion. I switched to a whole horizon
    years ago and have never considered going back. Having been an avid
    celestial navigator for over 20 years, my preference flies in the face of
    the commonly-held view that "beginners" prefer the whole horizon,
    while "experienced" navigators prefer the split horizon. I have used the
    whole horizon under various conditions of light and weather at sea and on
    land and never felt hindered in any way (maybe I am just too stupid to
    know better?).
    Having said that, I use my sextant extensively with an artificial horizon
    for practice on land, which may have a lot to do with my preference.
    Whole horizon mirrors seem to lend themselves to artificial horizons
    (both bubble attachments and external reflective) much better than split
    In the end, I think it is a matter of what works for the individual.
    >This matter of how light arrives at the eye via the unsilvered surfaces
    >the index mirror now seems to be resolved, to (at least) Ken Muldrew's
    >satisfaction. Others may yet find a scrap of meat remaining on the the
    >bone, to pick at.
    >To me, it seems to have shown all the best features of how a mailing-list
    >discussion ought to be conducted. Listmembers proposed various
    >tried them out, argued about the results, argued about the underlying
    >principles, tossed various ideas to and fro, in a spirit of courtesy and
    >mutual respect, to reach a conclusion.
    >"Well, he would say that, wouldn't he?" I hear you say, because my
    >suggestions were confirmed. But I think that all on this list are
    >open-minded enough to be prepared to change their stance, and their
    >in the face of strong-enough evidence and argument that points another
    >It's a real privilege to be a member of such a list as Nav-L. Thanks to
    >for raising an interesting question.
    >It leads me to wonder how quickly and successfully science and
    >understanding would have progressed, in the Days of Newton and Maskelyne
    >and Sumner, if they had been able to argue with their contemporaries by
    >email, instead of sending letters carried by packhorse and sailing ship.
    >contact George Huxtable by email at george@huxtable.u-net.com, by phone
    >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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