To Bermuda by sun linesJul 26, 2007
Some of the most memorable experiences in my sailing life were had aboard Ocean Star, the steel schooner once owned and operated by Ocean Navigator. It was my good fortune to be hired as navigational instructor for many of the passages and as captain for a few of them. When working as navigation instructor, under the capable command of captains like Deborah Hayes, Richard Bailey, and the indomitable Virginia Wagner, I made many passages back and forth to Bermuda, through the Caribbean, to the Dry Tortugas, and up to Sable Island. On board with the crew were six students - plucky, adventuresome men and women who wanted to experience going offshore in a solid vessel. They also wanted to learn celestial navigation, and during our week-long passages I would introduce them to the joys and frustrations of celestial navigation. We always had a ball, and every student, by the end of the week, had learned a lot more about the art of offshore passage making. Those days were great fun and a wonderful way to make friends with folks from all over the country.
This month's problem takes us on Ocean Star on a typical passage from Norfolk, Va., to Bermuda, about 630 miles away. This is a passage made in April of the year when the Atlantic is still as frisky as a kitten and the cold fronts sweep off the East Coast, making life cold and rough for the first few days. Our skipper is Virginia Wagner, and as first mate, the skilled and joyous Craig Gorton.
We will be doing a typical day's sights: Three sun shots, one in the morning, the next at noon, and the third in the afternoon. We will be doing a running fix and advancing our lines of position. This is excellent practice for many navigators who only shoot the sun. All these problems will be solved using the 2001 Nautical Almanac and Vol. 2 of HO 249.
All the following problems have the same constants. The Index Error on the sextant is 2' off the arc. The height of eye is 10 feet. There is no watch error. All times are given in GMT. The speed of Ocean Star for this problem is a constant five knots. All shots are of the sun's lower limb.
A. On April 15, Ocean Star is at a DR of 36° 20'N by 74° 50' W. The students come up on deck and take a lower limb shot of the sun. The shot is taken at 14 hrs 27min 15 sec. Hs is 46° 30.4'. Calculate intercept and plot LOPs. Establish Estimated Position.
B. Ocean Star is making five kts according to the taffrail log, which depending on sea conditions can either over- or under-read. Capt. Wagner has called for a compass course of 140°. Convert this to True. On this heading Ocean Star has a deviation of 002° E. The variation is 10° W.
C. What is the DR of Ocean Star for a calculation of noon? What time is noon?
D. What is latitude at time of sight which was taken at 16hrs 58min 10 sec. Hs is 63° 29.2'.
E. Create running fix and give new position.
F. At 20hrs 31 min the navigation students take another sun sight. What is new DR?
G. When the students take their sight Hs is 34° 55.6' and the time is 21hrs 31min 20 sec. What is the intercept?
H. What is the last EP?