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Silicon Sea Leg 68 results:

1.  Running fix at time of star shot = 8 49 N 46 40 W.

This question was not easy. The sun shot couldn't have been at 1031 UT
as stated -- zone time would have been 0731, way too early for the sun
to reach 66 degrees altitude! No, the sight must have been taken at
1031 zone time. That gave a reasonable (27 mile) intercept.

Instead of advancing the sun line several hours for the running fix, I
used the idea I floated a couple weeks back: immediately update the
estimated position. I moved the EP to the point on the sun line
closest to the old EP. From there I simply plotted a course line to
the star shot, where I again updated the EP, this time considering it
a running fix.

That star observation gave some trouble. I first thought the body must
be Pollux, but the intercept was about 4 degrees. Then I used HO 229
"backward" to convert Ho and Z to LHA and dec. With the latter values,
I searched the star table in the almanac for a match. Nothing came
very close, so as a long shot I tried Castor. That was it. Intercept
was about 25 mi. Azimuth was about 9 deg different from stated value,
though.

In real life, I'd be uneasy about basing a running fix on a
tentatively identified star, shot through a hole in the clouds.

2.  Compass course to Barbados = 310.

True course = 291, magnetic course = 309. My E-6B says we should steer
1 deg to starboard to counter the current. Besides, 310 is easier for
the helmsman!

3.  Distance to Barbados = 790 nm.

4.  DR at end of zigzagging = 11 06 N 56 00 W.

5.  True course = 302, distance = 230 from DR position.

6.  Date = May 19 at DR position.

7.  Mt. Hillaby should be on horizon at log reading 792 miles allowing
for current, 837 if current is ignored.

Distance to horizon is 66 mi for mountain. Add 3 mi for height of eye.
The 793 log figure includes 44 mi of drift (roughly toward
destination) during all the zigzagging. It also includes 8 mi drift
during run toward Barbados.

   

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