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    Re: 10 inch Slide Rule vs. Pocket Calculator
    From: Greg Rudzinski
    Date: 2009 May 28, 19:20 -0700

    A more favorable low altitude sight reduction simulation for the 10"
    K&E 4080-3 slide rule.
    
    Given:
    Declination 20 South, Latitude 35 North, Meridian Angle 50
    
    K&E 4080-3 unassisted
    .495 - .1962 = .2988   INV SIN = 17� 23' (0.55' high)
    
    K&E 4080-3 assisted by Bowditch table #31 for INV SIN
    .2988   INV SIN = 17� 23.5' (1.05' high)
    
    Trig 9 Digit Calculation:
    .494786489 - .196174695 = .298611794  INV SIN = 17� 22.4546'
    
    Trig 3 Digit Calculation:
    .495 - .196 = .299  INV SIN = 17� 23.9' (1.45' high)
    
    Trig 4 Digit Calculation:
    .4948 - .1962 = .2986 INV SIN = 17� 22.41' (.04' low)
    
    Conclusion: For low altitude sight reductions the 10" K&E 4080-3 works
    well without the need for a Bowditch table #31 INV SIN reference and
    seems to out perform a three digit trig calculator calculation.
    
    
    On May 27, 7:01�pm, 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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