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Subject: leg 56 results/problems
From: Paul Hirose (71202.2014@XXX.XXX)
Date: Sat Jul 24 1999 - 15:33:10 EDT
Here are my results from Leg 56.
1. not computed
2. 124 T, 1480 nm to Cape Horn from 1150 Z DR.
3. Mar 23 1848 ZT DR = 5049 S 8027 W.
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.
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.
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.
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.
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.
6. 122 T, 580 nm to Cape Horn from 0013 Z fix.
>From same plotting sheet as Q5.
7. Compass course 128.
8. ETA Cape Horn Mar 25 2340 ZT.
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.
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