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    Re: Using a slide rule for celnav
    From: Francis Upchurch
    Date: 2014 Jan 20, 23:21 -0800

    I use a homemade replica Bygrave for most of my LOPs, great circles and the second half of my lunar clearances (still can't do the first bit!see earlier postings. Any maths wizards please help!). Generally get within 1' of a calculator result and nearly as quick. I use a replica cylindrical Fuller for general cosine formulae and the lunar first bit (cosine formula). The Fuller is twice the size of the Byrave with vulnerable brass cursers and I've nearly finished a miniaturized version (similar size to Bygrave),with robust curser that is just as accurate (albeit with the aid of magnifying glasses to see the reduced scales.)This gives 4-7 decimal place accuracy with any formulae but a bit slower than the Bygrave.I've never tried using a 10" linear for cel nav. Very interested to hear it works better with Bygrave formulae.I will now try the mini Fuller using the Bygrave formulae. From what Gary has been saying, this may be even more accurate?
    I can send details in a couple of weeks on request.
    Another unanswered question, perhaps to Gary? The Bygrave is faster and just as accurate as Air Almanac in my experience, second only to modern calculators. why was it never standard issue during WW2? Only a few top RAF navigators used it and Chichester does not mention it in his RAF nav instruction books.
    Francis
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