Evanston: the sentimental sextant
Evanston: the sentimental sextant
Last night I bought a sextant, a little over forty years after I bought my first one. Both are the same U.S. Navy WWII model made by David White in Milwaukee. My first was a year younger than I, dating from 1942. This one was made near war’s end in 1945.
I paid $100 for the first, buying it in San Diego from a merchant marine officer who picked up second hand sextants from pawn shops in Panama and resold them in the U.S.
I paid $250 last night to win an auction at eBay. There were other newer sextants for sale there, but I wanted a David White.
I googled the value of $1 in 1970 and found it to be around $5.70 in today’s currency, so this one was even cheaper than the first. From the photographs, it appears to be in good condition; but if the arm has been bent, I may have nothing more than a moderately expensive wall decoration.
I’ll see--or half see--next week.
Of course when I bought that first sextant, google wasn’t a verb, and eBay and the Internet didn’t exist. Neither did GPS.
The decision to buy a sextant evolved during an exchange of emails with a friend in New Zealand about the iPad as chartplotter. Although I haven’t taken a sight in almost twenty years, I realized that I cannot let GANNET be the first boat I take to sea without a sextant. Counting the Garmin eTrex I brought back from THE HAWKE OF TUONELA, I have four handheld GPSs, as well as the internal iPad GPS and the external Dual antenna. They aren’t all going to fail. But the idea of Webb Chiles being lost in mid-ocean because he couldn’t take a noon sight for latitude is unthinkable.
In addition to the two David Whites, over the decades I’ve owned a Zeiss Freiberger sextant and two plastic ones.
My first David White, of which I was particularly fond because of our similar ages and its performance during my first circumnavigation, was lost when CHIDIOCK TICHBORNE pitch-poled west of Fiji.
After reaching what is now Vanuatu, I bought a plastic sextant, which I used for the passage from Port Vila to Cairns, Australia. It was accurate enough; but the index mirror had to be adjusted after every sight, so I replaced it with a metal Zeiss Freiberger in Australia. That sextant went down with RESURGAM.
I’ve owned THE HAWKE OF TUONELA only in the era of GPS. She has a never used plastic sextant aboard.
The problem with good metal sextants is that they are precision instruments expensive to produce for a minuscule market. Googling ‘David White sextant’ out of curiosity, I happened upon the eBay auction a couple of hours before it closed.
I taught myself celestial navigation from text books and developed my own simplified system using sun sights rather than stars or the moon. Even before my right eye’s implosion, I had a small scar on that retina which caused a star to vanish when I looked directly at it; and taking sights at dawn or dusk did not fit into the rhythm of my life at sea.
I learned that despite refraction tables, sun sights could not be trusted until the sun rose 20º above the horizon, which usually was between 8 and 9 a.m. locally. When conditions permitted--and as I approached Cape Horn in 1975, they didn’t for several days--I took a sight then and a second at local noon, combining the two for a running fix noon position.
With smooth seas and a clear horizon, I could trust that my position was accurate, though a pencil line on some charts was more than a nautical mile wide. In rougher conditions, it was acceptable to be within a five mile radius. Compared to a few feet/meters with GPS, this seems enormous; but in practice it only meant that I needed to keep a close watch for an extra hour or two when approaching land, something any sensible sailor would do anyway.
In addition to a sextant, celestial navigation requires exact time. Each three second error in timing a sight will result in a one mile error in position at the Equator.
When I started crossing oceans, precise time was usually obtained by signals received on a Zenith TransOceanic Radio the size of a small suitcase that required, if I remember correctly, nine ‘D’ batteries.
You also need sight reduction tables. I used H.O. 249, the simplified Air Sight Reduction tables developed during WWII.
The yearly Nautical Almanac.
A navigation protractor.
Dividers.
A pencil.
A chart.
And a chart table.
GANNET doesn’t have a chart table or any other kind of table or any flat surface big enough for a chart.
I’ll figure something out.
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Plans to anti-foul GANNET tomorrow have been foiled by the weather--thunderstorms are predicted--and by my evil eye, which is going to require more surgery. I’m delaying that until after GANNET’s scheduled launch on May 5, but have to go for a pre-op examination tomorrow, my third visit to a medical facility this week. My right eye as anchor.
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Having become addicted to sanding, I got my fix yesterday by sanding and water-sealing the deck on our small balcony.
Wednesday, April 18, 2012