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    Re: 10 inch Slide Rule vs. Pocket Calculator
    From: Gary LaPook
    Date: 2009 May 28, 02:48 -0700

    I decided to give this problem a try on several devices.
    
    On the MB-2A circular flight computer I got 66�.
    
    Using Dave Walden's ARG1 scale I got 66� 30'.
    
    Using a K&E 4080-3 and the sine-cosine formula I got 65� 48'.
    
    Using the K&E 4080-3 and the Bygrave method I got 65� 40'.
    
    Using the flat Bygrave I got 65� 41'.
    
    H.O. 229 gives the answer as 65� 39.9'.
    
    Using the Bygrave method on the 10 inch rule is definitely better than
    using the sine-cosine formulas.
    
    gl
    
    
    
    On May 27, 7:42�pm, Hewitt Schlereth  wrote:
    > 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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