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    Re: Difficult lunars from 1855
    From: Antoine Couëtte
    Date: 2016 Sep 18, 13:52 -0700

    Dear Paul,

    Concerning the 07 Sep 1855 Sun-Lunar you wrote:

    "  Compare his Sun lunar solution with modern solutions:

    08:09:01 Chauvenet

    08:11:46 Antoine Couëtte

    08:08:30 me (full solution)

    08:11:55 me (lunar time sight) "

    I have also computed this Lunar using ONLY the Sun and Moon altitudes given, and not making any use of the published position (N35°30'00"-W030°00'00").

    I am getting UT1 = 08h08m24.1s, a result directly comparable to your 08:08:30 "full solution" result.

    Since Sextant Distances vary at a rate of about 7.8" minute of UT1, this indicates that our data affected by refraction differ by about 0.8", which most probably entirely comes from the different Refraction values we are using.

    While you are using DE200/LE200 to its full accuracy, I am using INPOP2013 to its full accuracy also and both theories [should] differ by less than 1/100 arc second for the date considered.

    Interesting to see that in both cases - i.e. "Full Solution" and "Lunar Time sight" - our results differ by about the same quantity, with my UT1 determination happening slightly before yours by about 8 seconds.

    Good enough ... :-) 

    Best Friendly Lunarian Regards,

    Kermit

    PS: As you can see, in addition to the "Lunar Time Sight" mode, the "Full Solution" mode is also implemented in my software, but I [very] rarely use it. At least it enables me comparing own results with the "Classical Methods" Results, in the sense that -  in addition to the Sextant Distances - it also relies only onto the Bodies Heights and not onto the Observer's published positions.

       
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