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    Re: Mars - Mercury Question
    From: Frank Reed
    Date: 2013 Feb 7, 11:34 -0800

    Brad, you wrote:
    " As accurate as a lunar? No! Accurate enough to determine your longitude to a Prize value? I think we agree, yes!"

    Yes, but not "practicable" --that keyword that Harrison grew to hate. But again, in its favor, it has the unique attribute that it can be observed for longitude with only a telescope which was a more common device in some periods and locales than a sextant, so in that very modest sense it would have more practical than a lunar.

    "Now for that once in 250000 Year event..."

    Which reminds me. This topic and the previous one on the exact location of Polaris and its minimum distance from the NCP for the Merak-Polaris angle are both issues that interested Jean Meeus over the years. Many NavList members first encountered his very Belgian name as the author of "Astronomical Formulae for Calculators" which, when it was first published thirty years ago, became the bible of home-brew astronomical software development as well as handheld calculator work, a status which lasted nearly twenty years. While that book and his later "Astronomical Algorithms" are still occasionally useful, they have mostly been superseded in computing. Meeus wrote two other books that you'll like if you enjoy these sorts of "once in 250,000 years" events: "Mathematical Astronomy Morsels" and the aptly named sequel "More Mathematical Astronomy Morsels". There are a couple after that in the sequence, too. I recommend them, and they're definitely fun to browse if you enjoy this sort of thing (note: NOT navigation, but "mathematical astronomy" and things like the statistics of Venus transits, mutual planet transits, and so on). Since these are specialty books, they're available from a unique publisher, Willman-Bell. Here's a link to one of them: http://www.willbell.com/math/mc16.htm. You can also find used copies of some of his books at various online bookstores including amazon.

    -FER

    PS: Here is a brief bio of Jean Meeus: http://en.wikipedia.org/wiki/Jean_Meeus. I was getting ready to delete some completely un-necessary "implementation" links in this article until I saw the last one. Interesting... it was added in 2009 by an IP address located in Reno, Nevada. I will now demonstrate my psychic powers... :)


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