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    Re: Initial course nomogram
    From: Frank Reed
    Date: 2019 Oct 10, 11:16 -0700

    I believe that's the extended version of Weir's azimuth diagram. The azimuth of a celestial body is identical to the great circle "initial course" to the sub-star point (the GP). Diagrams like these were popular for celestial azimuths in the early 20th century but eventually they were superseded by simple one-entry table lookups. The Weir diagram in the auction item you found has been re-purposed for pure great circle work.

    There's nothing wrong with using Weir's diagram(s) for celestial sights today, and the files below are examples which I used for some classes a couple of years ago. They are copied from Bennett's "Complete Onboard" tables.  I'm also including an image of the Russian-language auction item for comparison.

    Frank Reed

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