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    Re: Calculator v. Slide Rule for Ex-Meridian Correction
    From: Francis Upchurch
    Date: 2016 Jan 1, 00:57 -0800

    Happy new year Greg.

    I'm intrigued by the accuracy you achieve with a pocket slide rule.I generally only get to 3 places on my 10inch linear, and therefore tend to use the Fuller 2 (4-7 places) for cel nav. I suspect like most of us you are a studeht of JS Letcher's Self Conatained Cel Nav withHO 218? 

    I learn't my first cel nav from it and Hewitt's Book Common Sense Cel Nav.) in the 80s and read it again every year, always learning something new. 

    I've always been a bit confused by his comments on page 92, suggesting that a standard (?10inch) trig slide rule is ok for clearing lunars with his formulae.

    Anyone got any comments on this? I've only done it with the Fulller2, believing you need as much accuracy as possible for lunars.

    What sort of results do you get with the intercept method and cosine formulae?

    Any ideas appreciated.

    Best wishes


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