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    Re: 10 inch Slide Rule vs. Pocket Calculator
    From: Hewitt Schlereth
    Date: 2009 May 27, 22:42 -0400

    That's neat, Greg, especially since the cosine part is all at the
    right end of the scale. I did it with a 10" rule w/o magnifier (under
    strong light) and got Hc=65�35' , reading right off the rule. -Hewitt
    
    On 5/27/09, Greg Rudzinski  wrote:
    >
    >  The following is a simulated slide rule vs. pocket calculator altitude
    >  sight reduction comparison for declination 20 degrees north, meridian
    >  angle 25 degrees, and latitude 15 degrees north. A 10 inch  K & E
    >  4080-3 was used for slide calculations. A hp 9s scientific calculator
    >  was used for 9 digit comparison.
    >
    >  Formula: Calculated Altitude = COSdec COSlat COSmeridian angle +/- SIN
    >  dec SIN lat
    >
    >  The slide rule method uses Bowditch table #31 for inverse SIN. A
    >  magnifying glass x2 was used to improve scale resolution:
    >  (calculation time 3 minutes)
    >
    >  .822 + .0885 = .9105    inverse SIN .9105 = 65� 35.0'  (4.9' low)
    >
    >  Trig pocket calculator calculation to 9 digits:
    >  (calculation time 90 seconds)
    >
    >  .822631444 + .088521326 = .911152770   inverse SIN .911152770 = 65�
    >  39.91'
    >
    >  Trig pocket calculator to 3 digits:
    >
    >  .823 + .089 = .912   inverse SIN .912 = 65� 47.0' (7.1' high)
    >
    >  Preliminary Conclusion: A slide rule with magnifying glass is equal to
    >  3 digit accuracy if Bowditch table #31 is used for inverse SIN.
    >  >
    >
    
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