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    Re: Bauer's book, was Re: Newton and Halley
    From: Frank Reed
    Date: 2007 Dec 03, 00:24 -0500

    Alex, you wrote:
    "Let me recall that Bauer's book contains several misleading statements and
    this is not only about history. This was discussed on the old list several
    years ago, when I just joined the list. I tried to test my new sextant with
    the star distances following Bauer's recommendations.
    As the list members immediately pointed to me these recommendations contain
    a substantial gap: he gives a table of distances, specially for
    sextant testing, but fails to mention that one has to correct for
    refraction. Refraction distorts star distances substantially, even if two
    stars have the same altitude."
    
    Well, not quite. He does indeed describe how to correct for refraction for
    stars in a vertical line. He also says that when stars are at the same
    altitude "refraction can be ignored" and that's not true, though the effects
    are usually smaller then. In this case, he was only repeating an error which
    was also present in venerable Bowditch at that time. And that's the case
    with most of the small errors in this book. They were common errors for most
    books on navigation written 20-30 years ago. They weren't his errors
    personally. Incidentally, except for rather gross checks on angles, the
    biggest problem with that table (and also the one in Letcher's book from a
    few years earlier) is that it ignores aberration which changes the star-star
    distances by as much as 0.6 minutes of arc during the course of the year. Of
    course, as you noted in another post, all of this is unimportant today since
    computation is dramatically cheaper today than it was back then and we can
    easily do the correct calculation when needed.
    
    The small mis-statement that most bothers me in Bauer is his recommendation
    that one should only shoot "mid-altitude bodies" because of the difficulty
    of swinging the arc at relatively low or relatively high altitudes. This is
    a misconception, but once again, it was an overwhelmingly common
    misconception at that period of time.
    
     -FER
    
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