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    Re: FW: Silicon Sea: Leg 79
    From: Dan Hogan
    Date: 2001 Sep 19, 7:35 AM

    On 19 Sep 2001, at 8:25, Russell Sher wrote:
    
    > Here are some answer attempts - any verifications?? My intercepts for Q3
    > seemed a bit long for some of the sights.
    >
    > Chart(s): Plotting Sheets
    >
    > Sight Reduction and
    > Dead-Reckoning problem     Leg 79  091701   Test your knowledge!
    > ----------------------     ------  ------   --------------------
    >
    > Our last FIX position was (03d 00.00'N  082d 00.0'W) {at} 10:51:11UT {at}
    > 26/06/2001. We are sailing toward MOP1(03d 00.0'N  110d 00.0'W) where
    > we will turn and head for Hawaii.
    >
    > At a Log distance traveled of 710.5 Nmi from the FIX position. TC 270.0d,
    > Speed 10.0 Kts, we determine that we have entered the Equatorial Counter
    > Current.
    >
    > 1)  What is the DR position on entering the Equatorial Counter Current?
    >
    > departure = 710.5 nm, since D lat. = 0.
    > Diff. Long in minutes = 710.5 *cos (3)), so D Long = 11 deg 49.5', so DR
    > long
    > = 093 deg 49'W
    > DR latitude  unchanged: so...
    > DR = 03 deg 00'N, 093 deg 49.5'W.
    > --  -------------------------------------------------------------------
    
    OK.
    
    Note to ALL. The accuracy of DR answers depends on the method of keeping
    track of the DR and the plotting accuracy. On Silicon Sea it was agreed on to
    use +/- 4 miles/minutes, anything less is dead on.
    
    > On the morning of 30/06/2001 we manage the following sights:
    >
    >         Body            UT/GMT          Hs
    >
    >         Fomalhaut       11:53:00        54d 01.8'
    >         Deneb           11:55:10        30d 03.8'
    >         Altair          11:57:20        27d 35.1'
    >         Saturn          11:59:05        23d 17.4'
    >         Venus           12:04:11        38d 50.8'
    >
    > 2)  What is the DR position at the time of the Fomalhaut sight?
    > --  -----------------------------------------------------------
    > distance travelled =  10 knots * 97.3 hours = 973.08 nmiles = departure (due
    > west) Diff. long in minutes = 973.08 * cos (3)=971.74' from DR 26/06/2001 D
    > Long = 15 deg 50.3', so DR long = 082 deg 00'W + 16 deg 11.7' = 098 deg 11.7'
    > W DR latitude  unchanged: DR = 03 deg 00'N, 098 deg 09'W.
    
    OK. You won't get lost.
    >
    > 3)  What is the position FIX?
    > --  -------------------------
    > using Navigator Light:
    > Lat:  03�32.2'N
    > Lon: 097�30.5'W
    
    OK.
    
    > Intercepts/Az For each LOP as follows:
    >
    >         Fomalhaut: 37.6' Away/Zn = 202 deg
    >         Deneb    : 4.6 To / Zn =  322 deg
    >         Altair   : 29.2' Away / Zn = 278 deg
    >         Saturn   : 50.2' To / Zn = 069 deg
    >         Venus    : 51.4' To / Zn = 072 deg
    >
    > -----------------------
    
    Thanks for submitting. Your answers are correct as far as practical
    navigating will require.
    
    Dan Hogan WA6PBY
    C27 "Gacha"
    dhhogan{at}verimail.com
    Nav-L Page: http://www.wa6pby.com
    

       
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