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    Re: Lunars and accuracy generally
    From: Frank Reed
    Date: 2013 Jan 3, 15:11 -0800

    Bill B., you wrote:
    "A question from the "no-nothing" cheap seats :-)"

    Ha! Bill, you are certainly not a "know-nothing"! In an earlier post, I used my expression "know-nothing know-it-all". Just for the record, this is a particular personality type which I am SURE you have encountered, but you have NOTHING in common with them. The latter is the sort who walks around museum exhibits loudly proclaiming nonsensical theories and telling his children that he "knows more than those so-called experts" and then proceeds to make a dozen statements that couldn't be more wrong, more nonsensical, declaring them to be "well-known FACTS!" He knows nothing --but he is confident that he knows everything.

    You wrote:
    "Your online almanac lists the Sun's SD as 16!27, yielding a diameter of
    32!54."

    I don't know if I would trust the hundredths digit in this case. I got 32.58 from a software source. What is the mean diameter of the apparent disk of the Sun? Do we have an accepted figure?

    You asked:
    "Does your SD calculation make any attempt at compensating for the
    irradiation fuzzy variable? If so, how?"

    No. Irradiation is a perceptual phenomenon. It got a great deal of attention in the 1960s among navigators and unfortunately the news never really trickled down. It isn't real, but the ghost refuses to stay dead. When I gave my presentation at the "leap second" conference last year, I had a chance to chat with Ken Seidelmann, editor of the Explanatory Supplement to the Astronomical Almanac. He asked me if I had done any experiments with irradiation. I said that I had, and I considered it a perceptual problem of no real concern if proper precautions are taken (use the right shades), and he told me about his experiments with a team from the US Naval Observatory when he was a young man in the 1960s. They were sent on a two-week beach "vacation" to the Outer Banks to perform sextant measurements to test out irradiation. They found it not reproducible though they found evidence of consistent personal error. But they had a great time on the beach! The real point of his story was that he made one of the "biggest mistakes of my life" when he got back to DC. When asked if he needed to make more observations, he said "no, our observations were sufficient" and thus turned down another opportunity for a junket on the beach with 60s girls in bikinis. Youth is wasted on the young. :)

    -FER


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