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    Re: GMT from Lunar Photo
    From: Antoine Couëtte
    Date: 2022 Jan 11, 09:16 -0800

    re : http://fer3.com/arc/m2.aspx/GMT-from-Lunar-Photo-Ritchie-jan-2022-g51881

    Hello to all,

    First I wish to thank all of you - Frank, Peter, Murray, Greg, Dave and Bill.

    Further to my queries, you kindly published multiple confirmations about the following stars identities :

    (1) - The 4 o'clock star  (HD202284) at 43.119' (Far Limb) as per my initial post,

    (2) - The 1 o'clock "occulting" star (HD202635),

    (3) - The 12 o'clok star (HD202672) at 2.84' according to Bill, and finally

    (4) - The 8 o'clock star still occulted (HD202578).

    I reworked them all with the following data : N31°55.8' / W109°07.2' Alt = 1,350 m and with the following extra assumptions :

    QFE = 850 hPa and T = +10°C (i.e. ISA + 5°C since we are in AZ ) .

    Hence getting the following results :

    (1) - GMT = 01h10m48s (updated from 01h10m49s) with : Moon LL = 15°45.8’ / 231.3° , Moon UL 16°18.5’ /  231.3° , HD1 = 15°52.8’ / 231.7° (from FER : 01h11m15s UTC from N31°55.58” W109°07’04” , and from Bill at 01h11m47s from the coordinates here-above)

    (2) - Occultation at GMT = 01h11m34 s with : Moon LL = 15°38.6’ / 231.4° , Moon UL 16°11.2’ /  231.4° , HD1 = 16°10.9’ / 231.5° (from Murray : 1:11:30.4 GMT)

    (3) - GMT = 01h11m31 s with : Moon LL = 15°39.1’ / 231.4° , Moon UL 16°11.8’ /  231.4° , HD1 = 16°14.6’ / 231.4° (from Bill at 01h11m40s)

    (4) -  Emersion at GMT = 01h13m55 s with : Moon LL = 15°16.4’ / 231.8° , Moon UL 15°49.0’ /  231.8° , HD1 = 15°23.1’ / 231.6° (from Bill : emersion at 01:15:05.)

    A bit surprised at the variable differences between Bill's results : 1 minute of time for (1) , 9 seconds of time for (3) and 1m10s of time for (4) . Probably something interesting to dig out. Bill, would you mind conctacting me here (I am also quite familiar with ELP/MPP02) ?

    For the MOON at UT = 01h15m I am computing and using RA = 21h21m17.51s , DEC = -20°42'36" , HP 59.796' =  while Full accuracy INPOP says : RA = 21h21m17.729s DEC = -20°42'35.59" Dist = 0.002451341 AU, i.e. HP = 59.794'

    Interesting to see hereafter the effect of Observer's Altitude for (2) and (4), everything else being unchanged (hence same 850 mb QFE in both cases) :

    For Occultation (2) : H = 1,450 m GMT = 01h11m34.3s  and H = 0 m GMT = 01h11m32.6s  Difference : 2.6 seconds of time

    For Emersion (4)   : H = 1,450 m GMT = 01h13m54.9s   and H = 0 m GMT = 01h13m51.2s  Difference : 3.7 seconds of time

    Best Regards to all,

    Antoine M. Couëtte

    antoine.m.couette@club-internet.fr

       
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