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    Re: Moon corrections: how computation order affects the result
    From: Eric Fernandez
    Date: 2020 Sep 2, 02:43 -0700

    Thanks Gary and others participating to this discussion.

    I hear what you say, but what I wanted to emphasize is that what you call the more complex method (serialising corrections, and calculating P-in-A at the end after adding the augmented SD) lead to the same result than the very simple formula, which on the contrary ignores the SD augmentation term and simply sums up all corrections calculated from an unmodified Ha. However, it is the summation of all corrections calculated from Ha plus the augmentation term that lead to a higher Hc in the end (by 0 to 0.3', aka the value of the augmentation). And that method of summing everything leads to Norie's corrections, in Capt- Khan Officer Handbook or in the navsoft software description (https://www.navsoft.com/html/corrections.html). Whereas the nautical almanach correction tables use more the unaugmented or augmented with P-in-A calculated after adding SD and augmentation. This is quite fascinating, because I thought that if one corrects for such small values (that would concern Moon SD augmentation, but also parallax of Sun (up to 0.15') or planets (up to 0.6') and even the oblateness correction) they would take care to use the proper calculation procedure, because these corrections only make sense if one follows a proper calculation procedure for P-in-A. So some procedural error may be perpetuated in some text books over the ages.

       
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