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From: Peter Fogg (no email)
Date: Fri Aug 22 2003 - 03:55:13 EDT
----- Original Message -----
From: "Dan Hogan" <>
To: <>
Sent: Tuesday, June 10, 2003 2:19 AM
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 @
> 20:20:30UT. TC 24.6d, Speed 10.5 Kts, Var 12dE, Dev 1dW, Current Set
035.0d,
> Drift 0.3 Kts.
>
> 1) What is the Compass Course(CC)/Course-to-Steer to MOP1(40d 00.0'N 155d
00.0'W)?
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 @
> 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?
is
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?
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