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    Re: Lat and Long by moon transit.
    From: Antoine Couëtte
    Date: 2011 Jan 28, 12:12 -0800

    RE :
    [NavList] Lat and Long by moon transit.
    From: Anabasis75---com
    Date: 28 Jan 2011 11:06

    Hello Jeremy,

    Thanks a LOT for providing us with a Moon LAN example.

    Provided that I have entered all numbers correctly (33 !!! shots are quite unusual, even for a former "Sextanthollah" like Kermit), here are the results I am getting :

    Observed Moon Transit (i.e. Moon "crossing" Moving Observer's Meridian, due South of Observer actually) happened at UT = 09h51m39.7s (LT = 18h51m39.7s)
    LAN Observed Position at this time was : N+21°49'5 E-130°03'7,
    Standard Deviation of Observations was 0.6 NMN, which translates into :
    Standard deviation on Latitude 0.6 NM (same value as above given great number of Observations) and SDEV for Longitude = 1.9'

    Observed Culmination Time was UT = 09h51m42.6s, only 2.9s apart from Transit time. Since the Ship south speed (-13'15 / hour) was almost the same as the Moon Declination south speed (-12.86' /hour), "the displacement [was actually] somewhat minimized" as you also indicated.

    Dead Reckoning our 09h51m39.7s LAN position into a position for 10:00:00 UT / 19:00:00 LT which was the time of your GPS Fix, we get :

    CelNav Observed Position at 19:00:00 LT = N21°47'6 , E-130°03'2
    to be compared with GPS Position for same instant at : N21°48'7 E130°07'5

    Overall Moon LAN Fix accuracy :

    in Latitude : 1.1 NM ( not quite 2 times Latitude SDEV), and
    in Longitude : 4.3' ( 2.3 times Longitude SDEV)

    Last Note : From my results printed listing I just checked (only one time though ...) my typed data which all seem correct (over 450 individual digits typed). Therefore the results I am deriving should be based on data correctly entered.

    Best Regards and Thanks again for your Contribution


    Antoine M. "Kermit" Couëtte

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