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After some passage of time and much perusing of my copy of
Bowditch (1966), the NAV-L archives, several websites,
and the solutions offered by Peter Fogg and Joe
(for which, thank you both -- they helped me spot my errors)
I have once again attempted Silicon Sea Leg 88,
with some success, I think.  Peter -- I disagree on the solution to part 5
(http://www.i-DEADLINK-com/lists/navigation/0308/0022.html).  You can't set
the Intercept to 0.

I am a self-taught beginner, and full of questions.
If you have any expert opinions on how these things are done in practice,
please post.  Much appreciated, as I am trying to become a navigator,
which will be a few steps beyond learning how to work these problems.

Though I worked it through to the end, I am left with some questions
+ For a leg of over 1600 miles across open ocean, does a skipper
    prefer a rhumb line course?  Why?  because it is easier and less
    prone to error?
+ Why does the navigator prefer to work with DR rather than EP?
    (easier?  less error? not important unless current gets stronger?)
+ I figured the Rhumb Line course from DR #1 towards MOP2 should
    be a course made good of 78.5 T.  If I attempt to compensate for
    current, that gives me a course to sail of 79.3 T, which agrees well
    enough with the 79d40.3'T sailings implied by the points given
    (DR #1 and DR #2) (bearing in mind that the navigator and I likely
    used different methods for DR work, as he likely had an
    appropriate chart, and I felt to lazy to construct a sheet of graph
    paper for the appropriate latitude).
+ Did the navigator use the current data during this leg?
   Or was it used to determine the course to steer between DR #1 and DR #2?
   What course did helm actually steer between DR #1 and DR #2, and why?

Thanks to everyone just for being there on the list.
It's been a fascinating (selective) read so far.

Renee

My answers:

1) DR #1 39d39.4' N 154d 42.4'W

2) ZT is 08:30:20

3)  I begin to get confused. "TC and Dist to MOP2"
    Since this is a distance of more than 1600 nmi,
    I presume that the navigator would choose a great
    circle course, broken into several legs.  Perhaps
    4 or 5 legs of ~400 nmi, or 7 legs (one per day?)
    In this case, there is not a single TC to MOP 2.
    Which implies, perhaps, Rhumb Line sailing.

  78.5d, 1652 nmi via the Rhumb Line
  67d, 1639 nmi via the Great Circle. (67d for first leg.)

4) Compass Course is calculated in each case.
    I presume it is also a good idea to correct for current.
    Rhumb Line: CC 69.5d (ignoring current) or 68d (correcting for current)
    Great Circle: CC 57d (ignoring current) or 55d (correcting for current)

       Which did the navigator choose?

5) arrive at DR #2 39d46.1'N 153d54.8'W, at 22:12:34 UT,
   and take a sun sight
    For this noon sight, Azimuth is assumed to be 180, dec = 5d06.8'

    Lat = 90-(Ho+Dec) = 40d08.3'.
    Intercept is 22.8 nmi Away

6) The unknown body must be Arcturus.  This would be more difficult
    if I had a "real" almanac to use.

7) The running fix:
    The course from DR #1 to DR #2 is 79d40.3'T
    So the navigator must have chosen rhumb line sailing!
    Using this course, DR #3 is 39d58.6'N 152d25.9'W

    The sight of Arcturus reduces to Z = 267 Intercept 20.8 Away

    From my plot, RFIX is 40d21.6'N 152d00.4'W

    I also did a quick check by approximating the Arcturus Z as 270,
    skipping the plotting to come up with an approximate fix of
    40d22'N 152d05'W, which is approximately 20 nmi from my "best"
    attempt at a fix.

Peter Fogg seemed to have completed the exercise without
any difficulties, but I found myself continuously mystified,
I suppose that, by the time I work all 87 of the 88 legs through,
I'll understand more about the habits of (at least) one navigator,
and won't be quite so mystified at every turn.

I have been using Navigate, v 1.5 by Rick Chapman
(using the default WGS 1984 ellipsoid) on my Palm V
for DR (though I have also attempted mid-latitutude graphing)
I get my celestial data for 2002 from the US Naval Observatory
http://aa.usno.navy.mil/data/docs/celnavtable.html
which also works Hc and Zn from an assumed position, which
is wonderful if you don't later decide (when the internet is out of
reach) that you made a mistake figuring the DR

   

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