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    Re: It's four-planet fix time...
    From: Lu Abel
    Date: 2018 Aug 5, 17:21 +0000
    By convention:

    Hs (usually abbreviated hs) is the raw sextant reading

    ha is hs adjusted for index error and height of eye -- ie, what someone with a perfect sextant with his/her eye at exactly sea level would observe.

    Ho is ha adjusted for refraction and other effects -- ie, a perfect observation in an atmosphere-less earth.

    So:  s = "sextant"  a = "apparent"  o = [perfect] "observation"

    We compare Ho to what one would get for an Ho if one were at one's assumed position; this is called Hc (c = "calculated" [if I were at where I think I am])

    On Sunday, August 5, 2018, 10:02:20 AM PDT, Antoine Couëtte <NoReply_Couette@fer3.com> wrote:

    RE : Its-fourplanet-fix-time-Rudzinski-aug-2018-g42485

    Dear Greg,

    Thanks for your shooting report and drawing.

    What do "Hs" and "Hc" stand for ?

    "Raw" instrument reading ? Which I suspect for "Hs"

    Corrected for Bulb Error ? (Which I suspect for "Hc" vs. "Hs") hence we would still need to correct for atmospheric refraction and parallax,

    Corrected for Bulb Error and atmospheric refraction ? Hence we would still need to correct for parallax ...

    Corrected for everything including parallax (i.e. geocentric value) ?

    Thanks in advance.

    Expecting to shoot all of them on the Western Coast of France shortly, maybe when Lady Moon is back in the night sky ...

    Very Best Regards


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