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    SD topocentric formula
    From: Eric Fernandez
    Date: 2020 Sep 10, 23:34 -0700

    Dear all,

    In my quest to understanding the calculations behind altitude corrections, I found several formulas for calculating the augmented SD or topocentric SD for the moon (the only body for which this may be important). In his guide on page 2-8 (available at https://www.celnav.de/page2.htm), Mr. Umland proposes several formulas. For instance, the approximate formula SD topo = k * HP * (1 + sin HP * sin Ho) can be found in many references (also as k*HP*(1+sin Ho/55) since sin HPmoon ~ 1/55). I also found an entirely different formula in an old Bowditch guide (the recent ones do not consider moon augmentation).

    However he also gives a rigorous formula (shown here as an attachment). I was wondering if anyone had any reference of where this formula comes from?

    Thanks a lot in advance for your insights.


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