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    Re: Traditional navigation by slide rule
    From: Noell Wilson
    Date: 2016 Jan 6, 18:18 -0800

    Here's the lower price end of the slide rule hierarchy -  Sterling 594. Still a log log. All plastic. Looks almost identical to a Dietzgen 1733 and some others with cheat sheet notes beside each scale. About $10 on eBay unless the seller is an optimist. 

    The log log scales are for calculating powers of numbers. The index - the 1 on the C scale - is set to 5 on the LL3 scale and close to 0.20 on the LL03 scale. 5^2 is 25 under the cursor on the LL3 scale. 0.2^2 is close to 0.04 on the LL03 scale ( not exactly lined up). Generally you read what's written on the LL scales instead of choosing where to place the decimal.

    If you wanted the square root of 5, you could either put the 2 on the C scale over the 5 on LL3 and read 2.23 under the index on the LL2 (tricky) OR put the index on the C scale over the 5 on LL3 and multiply by 0.5 to read the same answer in the same place.

    Log log scales aren't needed for CelNav. Only trig functions. Most USA slide rules have the trig functions on the slide. Some European ones have them on the fixed part. I suppose it depends on which you learned on.

    Noell



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