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    Re: Calculator v. Slide Rule for Ex-Meridian Correction
    From: Greg Rudzinski
    Date: 2016 Jan 3, 17:53 -0800

    For those that would like a go at a star ex-meridian Diphda and Ankaa are now in good position during evening twilight.

    Greg Rudzinski

    From: Greg Rudzinski
    Date: 2015 Dec 31, 11:15 -0800

    For a little fun on the final day of 2015 I did a time trial of the pocket trig calculator against the pocket 6" slide rule using the ex-meridian correction formula.

    a = 1.964 (Cos Lat.) (Cos Dec.) / Sin (Lat. +/- Dec.)   } contrary name +    same name -

    a(.267)(LHA t)(LHA t) = ex-meridian correction in minutes of arc added to Ho. The sum is solved as an LAN observation.

    a= 1.964(Cos 34°10')(Cos 23°4')/Sin 57°14' = 1.778 by calculator   1.78 by slide rule

    1.778(.267)(3.9°)(3.9°)= 7.22' by calculator   7.2' by slide rule

    The calculator took 58 seconds with 57 button pushes.

    The slide rule took 84 seconds with 6 moves of the slide and 6 moves of the cursor.

    The calculator wins by only 24 seconds. Practical accuracy is even.

    Greg Rudzinski


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