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    Re: Silicon Sea, LEG 13
    From: Mike Burkes
    Date: 2012 Sep 29, 13:20 -0700
    HI GR, rework yielded 39 09.4N, 11 00.2E which included advancing Sirius and Alioth to 1855 GMT.
    Mike Burkes
    626-833-1521
     

    From: gregrudzinski@yahoo.com
    To: NavList@fer3.com
    Date: Thu, 27 Sep 2012 19:29:13 -0700
    Subject: [NavList] Re: Silicon Sea, LEG 13

    Alberto,
    The first give away that something is wrong is the time of twilight. December 5th at 36 north will have civil twilight at 1714. Now lets transpose the 5 & 12 and we get May 12 th with a civil twilight of 1926 which is a good fit for this exercise. The attached plot works out pretty good for 12 May 1996. The navigator could have done a better job of star selection though.
    Greg Rudzinski

    [NavList] Re: Silicon Sea, LEG 13
    From: Alberto Najar
    Date: 27 Sep 2012 21:47
    Hi Greg,
    Sorry, here we go: my problem was with the question 1. I think there is some thing wrong with the data. The text is:
    "Sight Reduction and DR
    Dead-Reckoning problem Leg 13 XXXXXX Test your knowledge!
    ---------------------- ------ ----------------------------
    On 12/05/96 we are at DR(36d 13.9'N 10d 54.4'E), on a TC of 111.3d at
    7.8 Kts bound for Masabb Dumyat(31d 30.1.N 31d 50.0'E).
    It is 19-42-00 ZT. We decide on a set of 3 bodies for a FIX During
    Evening Nautical Twilight.
    Body Time Hs Zn
    Sirius 19-42-56 11d 46.2' 239.1d
    Alioth 19-48-27 61d 55.8' 035.8d
    Spica 19-54-40 31d 59.7' 137.5d
    1) What is our FIX position using Spica as the plotting time?
    What is the Dist Off?"
    If we work these sights we will find some thing very bizarre. I found:

    LOP for Sirius
    12/05/1996 19:42:56 GMT
    Assumed Pos. Lat:36°13.9'N Lon:10°54.4'E
    Hs: 11°46.2'
    Dip:-2.7' IC:-0.2'
    Ha: 11°43.3'
    Ho: 11°38.7'
    GHA: 65°20.5'
    Decl: 16°43.0'S
    LHA: 76°14.9'
    Hc: 0°46.9'
    Intercept:651.8 NM (towards)
    Az.calc: 248°

    LOP for Alioth
    12/05/1996 19:48:21 GMT
    Assumed Pos. Lat:36°13.9'N Lon:10°54.4'E
    Hs: 61°55.8'
    Dip:-2.7' IC:-0.2'
    Ha: 61°52.9'
    Ho: 61°52.3'
    GHA: 334°28.3'
    Decl: 55°59.0'N
    LHA: 345°22.7'
    Hc: 67°54.3'
    Intercept:-361.9 NM (away)
    Az.calc: 22°

    LOP for Spica
    12/05/1996 19:54:40 GMT
    Assumed Pos. Lat:36°13.9'N Lon:10°54.4'E
    Hs: 31°59.7'
    Dip:-2.7' IC:-0.2'
    Ha: 31°56.8'
    Ho: 31°55.2'
    GHA: 328°16.3'
    Decl: 11°08.6'S
    LHA: 339°10.7'
    Calculated Altitude (Hc): 38°43.1'
    Intercept:-407.9 NM (away)
    Az.calc: 153°
    Thank you very much,
    Alberto.

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