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    Re: Star-star distances for arc error
    From: George Huxtable
    Date: 2009 Jun 28, 08:52 +0100

    I had pointed out defects in Appendix G of John Karl's book, which affected
    the accuracy of its results to a user.
    Frank pooh-poohed these, writing- "But calling them "serious weaknesses"
    when there are simple solutions strikes me as a bit of an exaggeration.",
    adding "... it would take no more than an index card sized "errata" sheet to
    cover those particular items".
    Yes, of course, it would have been easy to put them right, if they had been
    anticipated. But, as there was no such errata sheet supplied with my copy
    (was there, with others?) there was no way a reader could avoid being
    misled. So: in what way does the potential ease of fixing those problems
    make them less serious as weaknesses, for the reader?
    As for Problem #2:, I had written- "No account has been taken of annual
    aberration, which varies cyclically over the year, and in the worst case can
    amount to errors in star-star angle amounting to 40 arc-seconds".
    And Frank responded-
    "OK, but the error should be no more than 20 arcseconds if the mean distance
    has been used (I haven't checked to see whether he did that or not). "
    He hadn't checked that, but I had. The mean distance hadn't been used. The
    distances were all based on a spot-value, at one arbitrary time-of-year. The
    possible error that I gave had been correctly assessed. So on what basis did
    Frank consider himself entitled to halve that number, without even bothering
    to check?
    This attention being given to appendix G distracts from the real value of
    John Karl's book, and I understand that in the new edition, this, and a few
    other matters, are corrected.
    contact George Huxtable, at  george{at}hux.me.uk
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    Navigation List archive: www.fer3.com/arc
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