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Chart(s): Plotting Sheets, Bass.gif

Sight Reduction and
Ded-Reckoning problem      Leg 42  061898   Test your knowledge!
----------------------     ------  ------   --------------------

On 25/07/1998 @ 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 @ 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 @ 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@mtrs x
2.07; Nmi = SQRT HE@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@wellspring.us.dg.com
        Ron Legere   - ronald.legere@yale.edu(Temp. Inactive)
        Tony Severdia- anthonys@pacbell.net
        Wes Murfin   - wmurfin@onslowonline.net (Cartographer)
        John Simmonds- mobi@netconnect.com.au
        Jim Manzari  - manzari@bluewin.ch
        Buck Godwin  - bgodwin@newsguy.com (Archive Files)
        Dan Hogan    - dhhogan@lightside.com


Dan Hogan WA6PBY
"Gacha" Catalina 27
San Pedro, CA
dhhogan@concentric.net
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