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    Re: Classic Trig Log Sight Reduction Revisited
    From: UNK
    Date: 2014 May 29, 06:51 -0700

    This inspired me to finish my "multiple ways to do sight reduction" in Excel. That said, I failed in getting Excel to recognize all the terms and to write everything so each step could be followed. The final result is a mix of Excel, longhand, slide rule, and calculator.

    I started this to illustrate how we ended up expressing negative logs as 9.xxx-10 but I ended up not answering that question. Someone smarter than me, and without a calculator, figured that the logCos of 42.175 Deg is -0.13012 and expressed that as 9.869875 -10. It's easy with a calculator but daunting without.

    Anyway, the attached is for a different problem, from an Ageton example, with:
    Lat 42_10_30
    Dec 23_06_24
    t 61_33_42 and an answer in Ageton of Hc = 36_01.5 and Az = 90.

    In the attached:
    First is the input, formula, and answer. Angles as decimal degrees for Slide Rule.
    Second is the result with a 10" plastic slide rule similar to a Deitzgen 1733. I was raised with a slide rule and I usually get surprisingly good results if the angles are mid-range.

    Third is Cos and Sin as decimals multiplied by calculator with my longhand result in a separate box to the right.

    Finally, a calculator used to get logs as negative numbers and making the calculation using those negative numbers. The calculations are repeated to the right in the standard 9.xxx -10 format of the Trig tables.
    Regards, Noell
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