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    Re: A, B & C Azimuth Tables Questions
    From: Greg Rudzinski
    Date: 2017 Feb 20, 06:59 -0800


    The 1938 part 2 copy of Useful Tables from the American Practical Navigator has no dedicated tables or forms designed to calculate azimuth other than table 39 Amplitudes. If mariners wanted to calculate azimuth then table 44 (log sines, tangents, and secants)  or 10" slide rule would have to be used.

    Here is what a tabular azimuth solution would look like using table 44 log secants.


    Lat. 27° 41' N  

    Dec.10° 58' S

    LHA(t) 57° 53'

    Hc 21° 57'

    Formula: Sin Z  =  CosDec  Sint  /  CosHc

    Log SEC Dec}   .00800

    Log CSC t      } +.07213

              Sum           .08013

    Log SEC Hc  } -  .03268

              Sum           .04745  Inv Log CSC

                       Z  =    63° 42'

    180° + 63.7°   =   243.7°  Azimuth

    Greg Rudzinski

    From: Doug MacPherson
    Date: 2017 Feb 19, 13:10 -0800

    I find the A, B, and C Azimuth Tables a great addition to my CN tool kit. I use the versions found in Norie's Nautical Tables.

    Does anyone know when these were first published in Norie's? Were they in the original edition back in the 19th century? I have never seen them in any editions of Bowditch. Was there a reason for this? Were they ever included in Bowditch?



    38-34N 121-38W

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