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    Silicon Sea No 87 problem
    From: Peter Fogg
    Date: 2003 Sep 6, 10:15 +1000

    ----- Original Message -----
    From: "Jared Sherman"
    >   current Silicon Sea exercise and then details of a problem I was having
    > the one before, and I have yet to hear a peep from any expert.>
    > Peter-
    >  But looking at my deleted files, the only one I still find from you re
    Silicon Sea 88 was one dated August 13th 16:00+10 and that one simply was a
    posting of the Silicon Sea questions plus answers. I didn't see any cover
    note, any query, anything at all besides a posting of a post.
    >  I know some folks have their email software set up to quote any message
    they are responding to, and I often see a "quote of a quote" with nothing
    else on a mailing list. I presume when that happens--when the entire message
    body is shown as a quote of another message, with no extra original
    content--that the sender has accidentally hit a SEND key, and I delete the
    message without further study.
    >  If that's the message you are speaking of, perhaps everyone ignored it
    because it was just a Q&A, with no question put forward attached to it?
    Just in case that message (posted on 22 Aug) got lost, here it is again.
    Despite the Subject, it refers to SS No 87.
    ----- Original Message -----
    From: "Dan Hogan"  Subject: Silicon Sea: Leg 78
    > Chart(s): Plotting Sheets
    > Sight Reduction and
    > Dead-Reckoning problem     Leg 87  060903   Test your knowledge!
    > ----------------------     ------  ------   --------------------
    > We are bound for Mid-Ocean Point 1(MOP1)(40d 00.0'N  155d 00.0'W). Where
    > we plan on changing our course toward Mid-Ocean Point 2(MOP2)
    > (45d 00.0'N  124d 00.0'N).
    > Our DR position was (29d 22.4'N  160d 54.6'W) on 07/09/2002 {at}
    > 20:20:30UT. TC 24.6d, Speed 10.5 Kts, Var 12dE, Dev 1dW, Current Set
    > Drift 0.3 Kts.
    > 1)  What is the Compass Course(CC)/Course-to-Steer to MOP1(40d 00.0'N 155d
    Answer: 1) CC= 13.3d
    So far so good.
    > We continue on TC 24.6d, Speed 10.5 Kts, Var 12dE Dev 1dW. On the morning
    > after our last DR position of(29d 22.4'N 160d 54.6'W) on 07/09/2002 {at}
    > 02:20:30UT. We manage a quick Sun sight through the broken cloud cover.
    Here I'm lost. If our DR was at 20:20:30UT on the 07/09/2002 then the
    morning after would be the 8 September? And if the time of the sun sight was
    at 02:20:30 UT then it happened precisely 6 hours later? Or was the DR pos
    simply restated with a mistake as to the time restated?
    Searching further for clues I notice the answer to
    3)  What is the Azimuth(Zn) of the SUN?
    3) Azimuth= 256.8deg
    which is a funny place for the sun to be in the morning but consistant with
    02:20:30UT on 8 Sep or 15:20:30ZT on 7 Sep.
    Using this assumption, the new DR for this time is N30d 20'  W160d 24'
    2)  What is the LHA and Declination of the SUN?
    My Dec is N05d 25.6' which is close enough to
    2) LHA= 227.2deg
       Dec= 5deg 25.4'N
    although my LHA, via one method, is 55d 19' and via the other 55d 20.3
     and the intercept is hundreds of miles too long.
    Is there a problem here? Or am I not understanding something?
    'PLEASE respond with your results and thinking on these exercises to
    the NAVIGATION list at large. If you have questions or problems, A
    lot of folks on the list are knowledgeable and willing to help. Any
    questions or doubtful areas will be responded to promptly. Let us
    hear from you soon!'

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