True Love and the Fading Art of Astral Navigation
Story By Capt. Gordon Reid
“What time does the moon set?” I asked. It was a set-up question posed after a bit of preamble and light banter.
She moved a fraction closer, made eye contact and stirred my soul. She was taller than I and a lot prettier. “Never though about it; what time?” she responded.
“About an hour later each day,” I quipped. “The rest of the stars and planets are on a 24-hour orbit. The moon is unique. She is in her own orbit; about 25 hours.”
It turned out later that she knew well what the Mayans had proven 3,000 years earlier, and what Galileo Galilei had been threatened by the Inquisition for declaring in the 16th century: The Earth is not the center of the universe or the solar system. In fact, the west-to-east spin of our planet makes the celestial bodies appear to be stuck on a celestial canopy in orbit around us. Our night sky is an illusion, but a convenient one for, we-the-navigators.
Linda was athletic, agile and equipped with 44-inch legs. She bounced aboard my boat with ease. She loved Scheherazade: the wide expanse of deck; the chrome, mica and mirrored interior; the neat low-aspect offshore rig; and the clean cockpit featuring a stainless steel destroyer wheel that I had wrapped in doe skin with baseball stitching.
“Is this how you track the stars?” she asked as she lightly brushed my sextant on her way past the chart table.
Over the next few weeks, I fear I created a monster. Linda and I became a couple. She became an accomplished sailor and helmswoman and she became obsessed with astro-navigation.
During World War II, sight reduction tables were published by the U.S. and the U.K. They are virtually identical. There are two versions, one for aviators and one for mariners. The mariners’ version became known as U.S. publication HO #229. The tables greatly simplify celestial navigation. They all but eliminate trigonometry from the calculations.
Mariners could now navigate with ease by measuring the angle of a celestial body above the horizon at a precise time. A simple calculation from HO #229 combined with data added from a current nautical almanac gives the navigator a bearing or azimuth to the body and a line-of-position (LOP) perpendicular to the bearing on which the vessel must lie. Linda embraced the concept, and she soon understood the process.
The stars are outside our solar system and must be treated differently from the sun and moon. They have their own set of sight reduction tables, sometimes known as “The Points Of Aries.”
Knowing the exact time is essential for calculating lines of position from celestial bodies. Greek mythology has it that the god Zeus rides his sun chariot from east to west across the sky. He completes his 360-degree journey in 24 hours, a velocity of over 900 nautical miles per hour. An error of one second during the timing of a sight results in a plotted position error of about four miles.
When possible, mariners keep two times on a boat: Greenwich Mean Time (GMT), also known as Zulu or Coordinated Universal Time (UTC) on the ship’s clock below. I adjust GMT every morning with a time-tick from the National Observatory in Colorado. And I keep local mean time (LMT) on my wristwatch or chronometer. I keep track of the chronometer error each day and update it with a time-tick at noon every Sunday. Knowing chronometer error is critical; one never knows when one will be navigating from a life raft.
The crew of Scheherazade fell into a weekend routine. We sailed into the Gulf of Mexico on Friday afternoons. We tacked on the wind, we reached, we set and jibed the spinnakers, practiced man-overboard drills and anchored off the beach. We faithfully shot sun lines during the day, moon lines if she was visible, and a round of stars sights at dawn and dusk. Linda would go below, concentrate on her calculations and announce our Lat/Lon with pride. Soon after, a gourmet meal would magically appear from the companionway. Good crew is hard to find.
The Mayans were not navigators of the seas, but they lived under the night sky and observed the movements of the stars and passed on knowledge generation to generation. They invented the “zero,” made sophisticated calculations, created a calendar and predicted celestial events, like eclipses far into the future. The Polynesians were the master mariners of history. Two thousand years before Europeans ventured across the Western Ocean, they navigated thousands of miles of open Pacific, with their entire families, to find tiny islands by the declination of stars.
It is believed that the Chinese, too, were master navigators. In 1421, they circumnavigated with three huge armadas consisting of hundreds of ships each. They explored most of our planet using Polaris and the Southern Cross as their main navigational aids and left their DNA footprint on most of the peoples of the world.
Linda’s first offshore navigator role came soon enough. We departed the boatyard in Tampa Bay on a promising evening after a full day of stowing supplies and last minute tasks. We cleared the Skyway Bridge at sunset and set course: 180 degrees for Rebecca Shoal. I took a reef in the main, balanced the helm, engaged the auto-helm and we reached south in a Force 5 westerly.
The night was glorious, but it had been a long day and our dead reckoning position was fresh; celestial navigation was tabled until the ‘morrow. We fetched Rebecca the next day and rounded north into the Gulf Stream. We set a course for Isaac Light and let the Gulf Stream set us north at a good clip. After a course change, we popped out of the Northeast Passage into the broad Atlantic hard on the wind in the dead of night.
A few hundred miles offshore, the night sky intensifies like nothing most landlubbers ever see. Brilliant planets and millions of stars appear down to horizon. Linda shot Polaris for latitude. Just before the purple dawn cracked in the southeast, she put my Rolex on her slender arm and pulled my sextant out of its mahogany box. She shot a round of stars before they disappeared for 12 hours. Her calculations became routine and flawless; no longer did I double-check her lines of position.
The night we cracked off the easterlies at 69 degrees west longitude and footed southeast for the Virgin Islands, the full moon exploded out of the sea in the eastern quadrant at full dark. I had watch below; Linda had the con.
“You better get up here skipper,” she sang out.
I had been anticipating her reaction to a full-moon rise at sea.
“It’s the moon babe,” I said, matter-of-factly from the companionway as I handed up a hot cup of Ovaltine.
“It looks like a bloody city. Can I shoot it?” she asked with customary gusto.
“Let it gain some altitude. You may not get much of a horizon.” I said, knowing that the reflection of the moon on the sea would probably wash out the horizon line. But Linda was getting good at rolling the sextant in order to allow the body to kiss the horizon with precision and averaging the visible horizon from the deck of a tossing sailboat at sea.
By the time we fetched the Silver Banks of Hispaniola, where Columbus wrecked the Marie Gallant (a.k.a. Santa Marie), my navigator-girl was bleary-eyed but fully graduated as an astro-navigator.
Captain Gordon Reid is a full-time yacht consultant based in Asia. He writes yacht related information and news articles for Triton Crew Newsletter, Divine Bali Bliss.com and other electronic and print media.