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    Re: Longhand Sight Reduction
    From: Hanno Ix
    Date: 2014 Jun 12, 10:45 -0700
    Francis, 
     
    Re: Fuller 2
     
    Could you please give me the details of your Fuller 2, particularly the scale: 
    - length/width of scale(s), 
    - diameter of the drum,
    - number of turns,
    - distance of finest graduation bars on both ends and their meanings e.g. 1.000 or 0.0005
     
    As an alternative: I believe you are printing the scales yourself, right?
    Could you possibly arrange for me to get a copy of the Fuller 2 scale?
    For now, accuracy and esthetics are irrelevant, I only would like to study
    the technical details. A Xerox would be fine.
     
    BTW: on my 20" slide rule the finest resolution is "2 bars per 1 mm". It is the on log10(x) scale. The bars are easy to read with the naked eye. A cos() - scale with " 2 bars per 1 arc min"  throughout would be ~100' long.  What is the longest scale on a cylindrical you know of?
     
    Re: Letcher's book. 
    Its referring to the 208, doesn't it? No I have not read it. Well, I do believe correct sight reduction including lunars can be done with 10" slide rules or the Poor - BUT only for a limited range of actual situations. I for one would not use them without knowing what the limitations really are.
     
    As I said, occasional success does not prove the general validity of any method.
    When you do know you are within the limits of simpler approach, though, use it!
    Your real challenge would be then to figure out the limits before hand.
     
    Re: Bygrave study. 
    I know my power with words is limited. I am an engineer, you know. However, if you stood right next to me at my terminal you would quickly and fully understand. And yes, the Bygrave is a great concept, mathematically and mechanically. The study confirms it will work reliably in a vast range of circumstances. And it bypasses those darn multiplications :)
     
    The advantages of the Doniol method are universal applicability, ubiquitous availability and  inherent simplicity. A clever high school kid could apply it right away, if given the formula, L,D,t and a cos() table -  without any prior instruction. His results would be very accurate.  Incredibly, there is only one -   1!   -  multiplication.   Hard to beat!
     
    Re: your health.  
    Best wishes!
     
    Hanno
     
     
       
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