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    Re: recommendation for slide rule ?
    From: Brad Morris
    Date: 2009 May 20, 11:25 -0400

    The slide rule was used everywhere, not just the moon landing.  Consider, the 
    electronic 4 function (+-*/) calculator was marketed the early 1970's.  I 
    still fondly recall my first calculator and marveled at the decimal digits 
    and the speed.  I wouldn't let anyone touch my precious instrument!  Any 
    engineering that was done before 1973 either used a mainframe computer or a 
    slide rule.
    
    Mainframe computers were gigantic beasts.  Nothing like the desktops of today 
    at all.  Remote operations happened (at least for me) at 110 baud.  Yawningly 
    slow.  Even when you were local to the mainframe, things took time.  You 
    submitted a job and the answer, after a period of time, popped out.  They 
    were expensive to operate and maintain.  Associated with the mainframe was a 
    staff. Your job was scheduled in, there was no instantaneous gratification.
    
    The slide rule offers immediate results, with an answer that almost always is 
    "good enough".  The 10" rules were like a sword on your belt.  Very awkward 
    to wear.  I still have my pocket slide rule which did not suffer from that, 
    at the expense of even further resolution issues.  I kept the 10" at my desk 
    and the small one in my pocket.  The small one popped out in meetings.
    
    The slide rule offers something that all the electronics in the world does 
    not.  It is the Order of Magnitude of the problem.  That is, you are forced 
    to estimate the answer in your head first and then stick the decimal point 
    where it belongs.  Essentially, you solve the problem before hand and the 
    only thing the slide rule does is to refine the decimal digits of accuracy.  
    Since you only have 2 or 3 digits after the decimal point (typically), you 
    are forced to be conservative in your calculations.  That's why many 
    structures that were created with slide rules appear to be "solidly 
    constructed". They were compensating for the inability to resolve the 
    problem.
    
    I don't want to discourage you, yet I believe that the solution to the 
    spherical triangle on a 10" slide rule will not be of sufficient accuracy to 
    suit for navigation.  There simply isn't enough resolution.  Dutton 
    recommends that each navigator equip himself with one, but I believe that 
    this is to perform simple rate equations and trigonometric solutions, not for 
    the solution of a spherical triangle.
    
    Mind, you will get a solution.  That solution will put you on the map.  The 
    only thing is just how accurate your answer is and how much do you need!
    
    Best Regards
    Brad
    
    
    
    
    
    -----Original Message-----
    From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf Of Greg Rudzinski
    Sent: Wednesday, May 20, 2009 12:50 AM
    To: NavList
    Subject: [NavList 8330] Re: recommendation for slide rule ?
    
    
    Gary,
    
         You have succeeded in getting me interested in slide rules. I
    have never owned or used one but after some internet research I see
    that they have been to the moon and back. Now I will have to get one!
    So far I am leaning toward the purchase of a Pickett N3-ES which is of
    aluminum construction. The slide rule could very well be the pinnacle
    of low tech achievement. Right there with the mechanical chronometer.
    
    Greg
    
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