A first celestial passageJul 19, 2007
It's been more than 30 years since I first heard the words "celestial sphere." At that moment my life was altered.
I was on a plane bound for Fort Lauderdale with my friend Steve Burzon, who cradled a brand new Plath sextant in his lap. We were on our way to join a 52-foot, center-cockpit ketch called Transition, designed by Pete Culler, on a delivery to St. Thomas. This was to be my first offshore passage. Burzon was navigator, and during the flight he explained to me, or at least attempted to, the concept of the celestial sphere. I was dazzled by his talk - or perhaps it was the rum I had before boarding. We were going to navigate to St. Thomas using just the stars and the sun.
My first offshore passage holds a very special place in my heart. Although Burzon and I aren't in touch any longer, the captain of the boat, Ken Hamilton, went on to become a good friend.
Not knowing any better and having virtually no experience, I made all the classic mistakes of a neophyte. I went shopping for the food and bought a 25-pound turkey that was about twice the size of the shipboard oven. I think we cooked that bird on San Salvador in a hotel kitchen. I also learned not to tie up a dingy with a half hitch and to never discuss politics on the night watch, especially with people I had just met.
Transition was a good boat, but it couldn't point well; we had a heck of a time making our easting. We finally cleared Great Isaac Light before Hamilton decided to slide off to the west and run down the Bahamas chain instead of trying to go east. Since I didn't know any better I thought this was the way all passages were made from Florida to St. Thomas. I recall that it took about 14 hours from when we sighted Puerto Rico until we made St. Thomas.
But we made it, and Burzon navigated the whole way using his new Plath. The powerful mystery, the simplicity and the beauty of converting numbers to position had a profound influence on my life. I am indebted to Burzon for introducing me to something that has given me great satisfaction.
So let's join Capt. Hamilton and Burzon aboard Transition some time in February, trying to get a star sight or two off Grand Turk Island. We are at 20° 53' N by 71° 08' W. Our Height of Eye is 10 feet. The day in question is Feb. 23. We will use the 2006 Nautical Almanac for this example. We will do two star sights using Vol. 1 H.O. 249, Selected Stars. The first star is Capella and the Hs is 28° 52'. The time of the sight is at 19:9:20 GMT. The next star is Altair. The shot was taken at 19:10:30. The Hs is 19° 45.2'.
We will be using Vol. 1 H.O. 249, Selected Stars, for the 2005 Epoch. The Hc for Capella is 29° 52' and the Zn is 46°. The Hc for Altair is 19° 40' and the Zn is 272°.
A. Reduce the Hs to Ho for both stars.
B. Using the time of the sights calculate the LHA Aires for the time of the sights. (You'll need the 2006 NA.)
C. What is the intercept of the stars?
D. Plot the position of the fix.