The challenge of sailing offshore, and the excitement and camaraderie that goes along with an ocean race, are why I have taken a navigator’s berth in nine Bermuda races. Four of those races have been Newport-Bermuda Races, but navigating the meanders and eddies of the Gulf Stream using celestial navigation keeps me coming back to the Marion-Bermuda Race on alternate years.
I first became proficient with celestial navigation while serving in the Coast Guard in the late 1970s, and since then I have used it to deliver yachts back and forth to the Caribbean (pre-GPS), taught dozens of classes ashore and at sea, and found Bermuda many times. Nonetheless, when my cousin Gregg Marston invited me to join a family crew for the 2015 Marion-Bermuda Race onboard his 1967-vintage 36ft Alden Mistral Ti, I knew I had to brush up on my skills, as it had been about 10 years since I last took my sextant out of its box. The crew consisted of Marston, his two sons, Chase and Jake, his brother-in-law Peter Stoops, and a close family friend John O’Meara. Collectively the crew had two dozen Bermuda races and lots of ocean sailing miles between them.
I spent weeks prepping for my navigator duties, calculating available stars and planets, studying Gulf Stream charts and weather forecasts, checking my sextant and watch for accuracy, and trying to remember what to bring in my sea bag. Final preparations for the June 19 start in Marion indicated a rough but fast ride. Ken McKinley of Locus Weather evaluated the weather forecasts, took into consideration the analysis from Jenifer Clarks’ Gulfstream forecasting service and recommended a course to the west of the rhumbline. This would best leverage a large meander in the stream and place us in position for the final dash to Bermuda.
Not really wanting to test the strong opposing winds and moderate current forecast for the Gulf Stream, we decided a course even farther west than that might pay off for us. Granted, we’d sacrifice the boost of that big meander, but we’d keep the boat sailing on her best angle and avoid the potentially steep head seas. As the third slowest-rated boat in the fleet, we knew that if we could just keep pace, our corrected time might give us a shot at a podium finish. That said, as navigator, I worried about getting good sights from the deck of a relatively small boat in the boisterous conditions that had been forecast. If we missed our routing plan due to poor navigation, well, no amount of Dark and Stormies in Bermuda would make up for that.
The first evening off Cuttyhunk I took a few sights of the crescent moon, two visible planets and a couple of stars and compared the Lines of Position (LOP) with the GPS. Finding that all agreed, I confidently turned off the GPS position display, and we were off to our first waypoint. After that began the steady work for me, with the seas building up through the weekend and the conditions getting pretty bouncy.
Sextant work is only one part of the job of a celestial navigator. Good navigation starts with good information, and that starts with the crew entering the relevant data into the logbook every hour. With that information the navigator can keep a diligent dead reckoning (DR) plot, allowing more accurate plotting of the celestial LOP. In fact, the DR plot is the baseline to which celestial LOPs are applied. A good DR plot, therefore, allows the navigator to confidently build running fixes by advancing LOPs, a common practice during the day when sun sights are the norm. The DR also keeps the navigator in the game during the night and in times of poor weather when sights are not available.
Beyond that, there are ways to leverage the mechanics of celestial navigation on the chart. The rhumbline course to Bermuda is roughly 165 degrees Magnetic, meaning that early morning and late afternoon sun sights (when the sun’s bearing is close to perpendicular to the course) generate LOPs that roughly parallel the course, thus providing good cross-track information. Sun sights took more toward midday (when the sun’s bearing is more due south), yield down-track information valuable for calculating rhumbline progress. A good round of star sights, on the other hand, provides a highly accurate fix “anchoring” the celestial navigator’s day in the morning and in the evening. I use a Celesticomp calculator to reduce the sights, the only way to go in my opinion.
I’ve found that it really pays to take a round of four to five sun shots at one time and plot all the LOPs. This technique, while more time consuming, makes bad sights more obvious when viewed alongside others that (hopefully) are accurate. The navigator has to interpret all of the celestial data, apply info from the log book, do some head scratching about predicted currents and weather, and then confidently (again, hopefully) recommend strategic race decisions.
Unfortunately, as we cleared the Continental Shelf and headed toward our first waypoint, I began having difficulty collecting enough data to accurately plot our position. The building seas, less than ideal horizons and my aging eyes were making star sights hard to come by, so I decided to rely completely on sun sights, and so began a lot of sun shots … about 75 of them in all.
Conditions were rough north of the Gulf Stream, with 12ft to 15ft seas and steady 20 to 30 knot south and southeast winds. This made for challenging (and wet) sight-taking, but I persevered. If the result didn’t look good, I went back out for another round to see if I could do better. The sextant also received several fresh water rinses in the galley sink after particularly wet times on deck.
Once I got into the rhythm of it, the sights came easier and the calculations made more sense. As we approached the stream, the plot showed we were, in fact, doing pretty well against our game plan, even if we seemed to be heading a bit farther to the west of our waypoint to enter the stream.
The conditions moderated as the wind veered to the southwest and we neared the stream, so we tacked to starboard and were able to sail pretty fast along the main axis of the stream for about 12 hours. My plot showed us hitting 10 knots over the bottom for half of one day, confirming the 2 to 3 knots of current boosting our 7 to 8 knots of boatspeed. We eventually shot out of the stream late on Sunday and headed to our final waypoint between two eddies, feeling pretty good about how we were doing. After that we had great sailing all the way into Bermuda, averaging 7.5 knots for the last 350 miles of the race. Pretty good for the old girl! One of those nights south of the stream was full of spectacular cloud-to-cloud lightning all around us, prompting O’Meara to grin and say from the helm, “It’s like sailing through a discotheque!”
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The GPS was turned back on 50 miles out from Bermuda (my last position was under five miles different from the GPS) and we sighted Bermuda early Wednesday morning. After a few tacks near the island, “The Mighty Ti” finished at about 0830 local time. Soon after we got to the dock at the Dinghy Club in Hamilton, we learned that we had won our class, the entire race, the celestial class and the Family trophy as well. As navigator on the winning boat, yours truly also won the Navigator’s Trophy, a reward for many years of shooting hundreds of sights and advancing DR’s along the rhumbline to Bermuda.
A Quick Look at Celestial Theory and Plotting
Celestial navigation solves a huge spherical triangle (the Celestial Triangle) for a specific time, with its points, sides, and angles defined by the position of the body, the nearest pole, and the position of the boat. (See Diagram #1.) This triangle can be represented both on the Terrestrial Sphere and on the Celestial Sphere with each point and line having a matching position on each sphere. As with any triangle, being able to define parts of it can help solve for the rest, and that is essentially what we do with celestial when we “reduce” a sight.
We’ll use the sun in our simplified description but the same theory holds for all celestial bodies. The navigator takes a sight with the sextant, measuring the sun’s height, or angle, above the horizon while recording an accurate time and also noting a DR position. Reducing the sight solves the triangle for that instant in time using a nearby “assumed” position of the boat, information about the position of the body derived from the Nautical Almanac (or preloaded into a computer or calculator) and some basic calculations. Ultimately this process yields the navigator with a bearing to the sun and a sextant angle from the “book.” After some manipulations to compare this data with what the navigator observed, an LOP can be drawn on the chart.
The plotting of the LOP is central to the navigator’s ability to make sense of all the calculations. To simplify the theory, imagine that the sun is sitting on top of a flagpole. The spot where this imaginary pole is planted in the ground is known as the Geographic Position (GP) of the sun. Standing at that spot a navigator would record a sextant angle of 90 degrees (the sun would be directly overhead). Move away from that spot and the sextant angle decreases, eventually reaching zero as the sun on top of its theoretical flagpole falls below the visible horizon.
Sextant angles can also be represented by a huge circle around the sun/flagpole with the GP at its center and every point along that circle yielding the same sextant angle. (See Diagram #2.) Think of a fleet of sailboats whose navigators all record the same sextant reading at the same time—they’d form a circle around the sun; our navigator must figure out which boat he is aboard. These Circles of Equal Altitude can be thousands of miles in diameter, so we cannot plot them in their entirety on our chart. But if we zoom way into a scale that fits our little nautical chart, we can imagine that the circle appears to be a straight line. That straight line is perpendicular to a radius of the circle drawn to the GP. The radius described is actually a bearing to the sun, and the straight line (representing our little portion of the huge circle) becomes the LOP.
Celestial sight reduction gives the navigator enough information to draw those two lines and by applying the DR information that he has of course carefully plotted he will be able to pick a spot along the LOP that corresponds to the boat’s actual position. It really is elegant in theory and simple in execution, even if the theoretical underpinnings can seem a bit obtuse at first.
Celestial Navigation tips
- Take a course. Having a teacher available when you have a brain cramp is very helpful.
- Celestial navigation doesn’t require a lot of math—just addition and subtraction—unless you want to fully understand the spherical trigonometry.
- Brush up on basic piloting skills (DR, tides and currents, compass correction, chart work, etc.). Without that background you will have a tough time with celestial navigation, so put down the GPS and (re)learn traditional piloting and charting.
- The ability to identify every star in the sky is not a prerequisite. Truth be told, you’ll probably use less than 10 stars in a typical voyage.
- Learn how to do the calculations longhand, but definitely, use a celestial calculator like the Celesticomp (my personal favorite). The drudgery of reducing a voyage worth of sights “by the books” can exhaust the navigator in the best of times.
- Buy a “real” sextant … a metal one. A quality instrument provides more pleasure, better accuracy, and will last for generations.
- Accurate time is critical to celestial navigation. You don’t need an expensive watch, just one that has predictable accuracy.
- Practice, practice, practice. Studies have shown that accuracy continues to improve even after thousands of sights.
- Celestial can be a primary method or an accurate backup: the U.S. Naval Academy and U.S. Coast Guard Academy have just reinstated a celestial requirement for cadets, an admission that, yes, the GPS system could fail.
- Embrace the art and skill of celestial navigation. While it is challenging and rewarding, it can be used anywhere in the world with the proper tools.
Tools of the Trade
A new metal sextant will set you back anything from a few hundred dollars to a few thousand; it will be cheaper to buy a good used or refurbished instrument. An entry-level plastic sextant can be found for around $250. Talk to an expert before deciding which one to buy. You’ll also need an accurate digital watch, as well as a nautical almanac, a set of sight reduction tables, a pad of universal plotting sheets, your favorite plotting tools and perhaps a Star Finder. A specialized celestial calculator will allow quick sight reduction. For general reference, “The Sextant Handbook” by Bauer is a classic. An investment of $500 will get you started, more if you opt for a high-quality sextant. For sextants and navigation tools, try Celestaire (celestaire.com), Landfall (landfallnavigation.com), Starpath (starpath.com), Davis Instruments (davisnet.com) and Weems & Plath (weems-plath.com).
When Andrew Howe is not racing to Bermuda or skiing in the New Hampshire mountains, he sails with his family in Maine aboard an Allied Seabreeze sloop