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    Re: Azimuth discrepancy?
    From: Greg Rudzinski
    Date: 2013 Mar 17, 16:43 -0700

    Alan,

    Arc Sin [ (Cos 29.5533)(Sin 46.2733) / Cos 31.2266 = 47.3* = Z

    180* + 47.3* = 227.3* azimuth

    Seems to be the same as USNO


    Greg Rudzinski

    Azimuth discrepancy?
    From: Alan S
    Date: 2013 Mar 17, 16:06 -0700
    Using Jeremy's raw sextant data for Fomalhaut, on 13 January, 2013, listed in his March post as follows:

    Watch Time: 19:12:24

    Hs: 31D 19,9M

    Height of Eye: 83'

    Index Error: 0.9 On Arc

    ZD: -8

    DR: 08D 50.0M North x 109D 40.0M East

    Temp: 80D F.

    Bar. Press.: 1013MB HG


    Using the 2013 Commercial edition Nautical Almanac Daily Pages and LOC Method for Sight Reduction, I got the following:

    LHA: 46D 16.4M

    Ho: 31D 09.9M

    Hc: 31D 13.6M

    Dec: 29D 33.2 South

    a: 3.7 NM Away


    Zn 240D


    I made no adjustment for temp. or pressure.

    The above results seem ""Kosher"".

    Using U.S. Naval Observatory Gastronomic Applications Department Celestial Navigation Data, for the time, date and DR coordinates given, I got the following results:


    GHA: 296D 36.5

    Dec.: 29D 33.2M South

    Hc: +31D 13.5M

    Zn: 227.3D, call it 227D

    Differences in GHA, Hc and Dec, being 0.1M seem minor, however a difference of 13 D in Zn seems significant and leaves me curious. Clarification or explanation please.


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