November 25, 2008

Light and sweetness

EVERY TIME I flick through the West Marine catalog my eye is stopped by those beautiful brass kerosene anchor lamps. The Dutch firm of Den Haan has been making these anchor lamps for more than 75 years.

They have Fresnel lenses, bails top and bottom, and safety guards. They’re thorough seagoing lamps, fit to make any sailor swoon.

But, the last time I looked, there was a line in the catalog that made me grind my teeth: “Not Coast Guard approved to mark a boat at anchor.”

Well now, so what? Who needs Coast Guard approval?

According to the International Regulations for the Prevention of Collisions at Sea (the Colregs), if you have a boat less than 164 feet in length and you put out an all-round white light that can be seen for two miles, it’s a legal anchor light.

It doesn’t have to be electric. The Colregs say so. A flame from a kerosene lantern with a wick half-an-inch wide and a half-inch high will do the trick.

To be visible for one nautical mile, a light needs a brightness of just under one candela.
Here are other distances and the brightness required:

2 /4.3
3 /12
4 /27
5 /52

And what, you say, is a candela? Hell, I was hoping you wouldn’t ask. It’s kinda boring. But if you must know, read on.

The candela is the metric system’s base unit of luminous intensity. You can think of it as one candle-power. It’s pretty close. So you’d need an oil lantern the equivalent of 4.3 candles to be seen two miles away. Or five candles in a glass jar, for that matter.

Meanwhile, you might want to memorize the official definition of a candela, so you can blurt it out through gritted teeth when the Coast Guard sits you down in front of the spotlight and grills you about your “non-approved” anchor light:

“The candela is the luminous intensity, in the perpendicular direction, of a surface of 1/600,000 of a square meter of a black body at the temperature of freezing platinum under a pressure of 101,325 pascals.”

The Coasties will be astonished at your knowledge, not to mention humbled and amazed, so now is your opportunity to take advantage of the situation. Tell them to move off a distance of two miles to confirm that they can indeed see your anchor light.

As soon as they leave, blow out your lantern and slip away into the darkness.

(PS: Don’t mention my name in connection with any of this, or there will be serious consequences.)

Today’s Thought

And the light shineth in the darkness; and the darkness comprehended it not.
--New Testament: John i, 5


“Where did you get that nice new anchor?”
“Well, I was going to my boat yesterday when this beautiful blonde came along carrying a 25-pound CQR. When she saw me, she threw it to the ground, took off all her clothes, and said: ‘Take what you want.’”
“Ah, good choice. The clothes probably wouldn’t have fit you anyway.”

1 comment:

Oded Kishony said...

Hi John,

Hope you have a great Thanksgiving.
I've long longed for one of those lovely anchor lights, but I've settled for a small kerosene 'hurricane lantern' which seems to work ok. I've also used an led lantern which seems a bit safer.

Warmest regards,
Oded Kishony