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    10 inch Slide Rule vs. Pocket Calculator
    From: Greg Rudzinski
    Date: 2009 May 27, 19:01 -0700

    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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