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    Silicon Sea: Leg 42
    From: Dan Hogan
    Date: 1998 Jun 18, 2:45 AM

    Chart(s): Plotting Sheets, Bass.gif
    
    Sight Reduction and
    Ded-Reckoning problem      Leg 42  061898   Test your knowledge!
    ----------------------     ------  ------   --------------------
    
    On 25/07/1998 {at} 11:47:13ZT the our DR was(37d 18.0'S  124d 48.9'E). We
    had managed a Noon Sight for the latitude.
    
    When taking the Noon Sight the navigator discovered that the
    Knotmeter's needle was pegged to the zero pin. We trail the Walker Log
    Meter off of its stern mounting position and set it to zero miles. The
    Walker Log can be read with accuracy to the nearest tenth(000.1) of a
    mile.
    
    Our TC 97.5d, Var 0dE Dev 2dW. In the evening, through a break in the
    clouds, we get a sight of an unidentified and not very bright star.
    Its bearing is just a bit to starboard of dead-ahead.
    
     GMT		Body			Hs
     09:35:20	Unidentified	30d 00.4'
    
    1)  What is the DR position?
    --  ------------------------
    
    2)  What is the name of the star?
    --  -----------------------------
    
    We plot the star sight and advance the 25/07/1998 {at} 11:47:13ZT Noon
    Sight (37d 18.0'S) to the time of the star sight.
    
    3)  What is the Running FIX(RFIX)?
        What distance should the Log read?
    --  ----------------------------------
    
    4)  What is the TC and Dist to Bass Strait(39d 18.0'S  144s 00.0'E)
        from the RFIX?
    --  ---------------------------------------------------------------
    
    5)  What is the Compass Course to Bass Strait?
    --  ------------------------------------------
    
    We have a solid overcast of cirro-stratus clouds, but otherwise the
    weather is slowly improving. Wind is Force 7. We sail on holding our
    course, without any fixes.
    
    On 29/07/1998 {at} 17:53:00ZT with the log reading 920.5mi since our
    RFIX,the top of a mountain becomes just visible about 3 points off the
    port bow. Looking at our charts we see that it must be on Wilson's
    Promotory, a 755mtr high mountain at (39d 02.0'S  146d 17.0'E), on the
    SE tip of Australia.
    
    We have entered Bass Strait. Off to starboard and below the horizon
    lays Tasmania; to port, the Australian mainland. Ahead of us are the
    Kent Group Islands and Flinders Island.
    
    6)  What is the DR position at this time?
    --  -------------------------------------
    
    7)  What is the visible distance of the mountain top on Wilson's
         Promotory?
    -- -------------------------------------------------------------
    
    8)  Should the mountain visible from our current DR position?
        What is the distance to the mountain?
    --  ---------------------------------------------------------
    
    Note:
    Lat & Lo = XXd XX.X', Date=DD/MM/YY, HE 8 Feet, Index correction
    -.2', Time hh:mm:ss in UTC/GMT. Silicon Sea is a medium displacement
    sailing vessel, 40 Feet LOA. 38 Feet LWL; Cutter rigged. Looks a lot
    like a Mason. Can tack to 45d. Dist to Horizon: Nmi = SQRT HE{at}mtrs x
    2.07; Nmi = SQRT HE{at}ft x 1.17. Water Tank = 60 gal(Imp.). Fuel Tanks=
    90 gal (Imp.). Fuel consumption .450 gal/Hr at 8.3 Kts.
    
    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!
    
    Good Navigating!
    
       -=The Navigation List Working Group=-
    
            Peter Smith  - psmith{at}wellspring.us.dg.com
            Ron Legere   - ronald.legere{at}yale.edu(Temp. Inactive)
            Tony Severdia- anthonys---.net
            Wes Murfin   - wmurfin{at}onslowonline.net (Cartographer)
            John Simmonds- mobi{at}netconnect.com.au
            Jim Manzari  - manzari{at}bluewin.ch
            Buck Godwin  - bgodwin{at}newsguy.com (Archive Files)
            Dan Hogan    - dhhogan{at}lightside.com
    
    
    Dan Hogan WA6PBY
    "Gacha" Catalina 27
    San Pedro, CA
    dhhogan{at}concentric.net
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