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    Re: Lunar-Distance correction for Oblateness
    From: Sean C
    Date: 2018 Apr 6, 18:00 -0700

    Frank,

    You wrote:

    "...Sean even posted that altitude correction which is taken directly --verbatim-- from the pages of the Nautical Almanac. This is wrong. This is not how you correct a lunar distance for oblateness."

    To be clear, I have never used this correction. I've always stuck to the method outlined on your "Easy Lunars" page (with great results). I only included it with the N.A. formulae because it was there. Which leads me to wonder: If the N.A. oblateness correction affects the HP - and if the HP is used in the lunar clearing formula - then why is it not useful in that context ... even if oblateness affects the lunar distance in another way? Is it because the N.A. correction is so small that it is inconsequential? Or is it because the effect that it has on the HP is simply irrelevant to the clearing process? I remember you writing that the actual correction was ignored by pretty much everyone during the time lunars were in use, but I'm curious as to why the N.A. correction isn't needed.

    In retrospect, I probably should not have included that particular formula in my response to Ed Popko. Especially considering the fact that I don't use it. But, I do remember you saying at some point that we are trying to squeeze as much accuracy as possible out of a lunar. That's why I'm curious about the N.A. correction. I would investigate it myself, but with my very limited math skills I wouldnt even know where to begin. Thanks!

    -Sean C.

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