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    Re: leg 56 results/problems
    From: Dan Hogan
    Date: 1999 Jul 24, 18:37 EDT

    >Here are my results from Leg 56.
    >
    >1.  not computed
    >
    >2.  124 T, 1480 nm to Cape Horn from 1150 Z DR.
    OK
    >3.  Mar 23 1848 ZT DR = 5049 S 8027 W.
    A tad off, but what are you using for Sailings calculation?
    >Q1 and Q2 were worked on a plotting sheet I drew on a piece of typing
    >paper, scale 6 nm per mm.
    >4.  Mar 24 0013 Z fix = 5131 S 8105 W.
    OK
    >Sight reduction by HO 211.  Regulus was the unknown body observed at
    >00:14:30 Z.  Identification by 2102-D star finder, described in
    >Bowditch.  Confirmed by Regulus LOP matching other LOPs.
    Yes
    >Other unknown body probably Miaplacidus.  Did not reduce this sight,
    >as the angle of cut with the other LOPs would have been poor and I
    >felt an additional LOP not worth the bother.
    Yes
    >LOPs were plotted on a 3 mi/mm plotting sheet centered at 50 S 83 W.
    >This allowed the DR, fix, and Cape Horn to fit on one piece of typing
    >paper.
    >
    >5.  Total compass error = 27 W.  Variation 3 W.  Not sure why we're
    >asked for variation, since it's stated after Q6.
    Did you get the revised edition of Leg 56? I had made a gross error in
    the initial issue.
    >Compass error based on the Regulus bearing vs. predicted bearing at
    >the fix position (from HO 211).  The Miaplacidus (?) bearing was on a body
    >at 66 deg altitude vs. 14 for Regulus, thus I felt it less suitable for
    >determining compass error.
    Right
    >6.  122 T, 580 nm to Cape Horn from 0013 Z fix.
    Close, Ok if you are doing it the hard way, without using the Sailings.
    >>From same plotting sheet as Q5.
    >
    >7.  Compass course 128.
    Hmm check this.
    >8.  ETA Cape Horn Mar 25 2340 ZT.
    OK on date.
    >
    >Current is 1 kt dead on our stern for practical purposes.  Speed/time
    >computation via E-6B aviation slide rule.
    >
    >
    >All the above was written before I looked at the answers.  It looks
    >good except for Q5 and Q7.  To determine compass error, I assumed we
    >were supposed to compare the compass bearing of a celestial body to
    >its computed azimuth.  I used Regulus, whose Zn at the fix coordinates was
    >49.  Compass bearing was 22, so compass error was 27 E, not 27 W as I
    >stated.  But this still doesn't match the answer, 15 E.  How do you get
    >that?
    >
    >Right before Q7 we're told, "Our Var is 3dW".  Was this a trick to see if
    >we would disregard unreasonable data?
    >
    >The error in my ETA is due to my distance being 3.5% high.  That's
    >more than I like, but I suppose it's unavoidable when using a plotting
    >sheet for a 550 mi leg at high latitude.
    >
    Dan Hogan WA6PBY
    dhhogan@XXX.XXX
    Navigation-L: http://nav.cnchost.com
    

       
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