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    Re: Sight reduction methods
    From: Gary LaPook
    Date: 2015 Nov 3, 15:38 -0800

    Here is a link to the flat Bygrave:




    Re: Sight reduction methods
    From: Frank Reed
    Date: 2015 Nov 3, 13:58 -0800

    Hi Dale,

    Welcome aboard (if you haven't been welcomed enough yet). There are dozens and dozens of sight reduction methods. Some deserve the name, some don't. Some methods of sight reduction don't have names at all. Others deserve to be split in two.

    You mentioned "law of cosines" as a method of sight reduction. May I ask, where did you pick up that terminology? I've heard it from quite a few people recently, and I'm curious to learn why people began referring to a basic mathematical equation as a "method of sight reduction". It's a bit like saying "addition" is a method of sight reduction. :) There are many procedural techniques founded on the law of cosines. Each of them could be counted as a distinct method of sight reduction.


    And you should learn about the hav-Doniol method which was a subject of much discussion among NavList members a few months ago. It's a short method that requires one longhand multiplication but in trade it gets by with only a short mathematical table. It's efficient and convenient if you want a paper and pencil approach. You could also experiment with various slide-rule style sight reduction methods like the Bygrave cylindrical slide rule and Gary LaPook's "flat Bygrave". The options go on and on...

    Frank Reed
    Conanicut Island USA

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