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    Re: A, B & C Azimuth Tables Questions
    From: David C
    Date: 2017 Feb 21, 00:26 -0800

    According to Blackburne the ABC tables can be used for more than calculating azimuth. Here are the claimed uses:

    • Find azimuth
    • Find error in long due to an error in lat when working a time sight.
    • Find initial great circle course.
    • Find great circle distance
    • Find meridian of GC vertex
    • Find latitude of GC vetex.
    • Find a succession of points on a GC to plot track on a Mercator chart.
    • Find the long of the point of tangency of the arc of a GC with the limiting parallel of lat (as in NZ to Cape Horn)
    • Windward GC sailing.
    • Identify an unknown star.
    • Given lat, dec, hour angle find the alt.     ...............Use for intercept method???
    • Find reduction to the meridian (in conjunction with ex-meridian tables)
    • Find hour angle of maximum altitude with A and B tables  .............Investigate this?

    The calculation of azimuth and the calculation of initial GC course are the only uses I have put the ABC tables to. I have marked two other uses that IMHO deserve further investigation. When working an intercept I determine the azimuth with the ABC tables. If I have interpreted what Blackburne has written correctly then I can also calculate Hc by ABC tables. i.e. the ABC tables and the NA are the only volumes I need for astro. It seems too good to be true. I suspect that the interpolation required and the low precision would make this method impractical except in an emergency.

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