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Burch at the Helm

Lunars! For the celestial who has everything: A challenge, that when met, will put you in the company of Bowditch, Cook and Vancouver

ack when I had more you will be prepared for any of the technique in the traditional man- money and than various Doomsday scenarios (e.g. ner without computers has recently I do now, I took up the no more GPS, radio time signals, become convenient with a new sport of flying. In the computers or iPhones). In fact, with publication of the Stark Tables for process, an instructor a few special tables printed out and Clearing the Lunar Distance and Bconvinced me that to be a safe and stowed, you could navigate—with Finding Universal Time by versatile pilot, I should take train- sextant alone—to any point on Observations—Including a Con- ing in aerobatics. This led to some for the next 20 years, even if there venient Way to Sharpen Celestial exciting hours behind “the stick” of a were no more civilization at all. Skills While on Land. This Champion Citabria, strapped into a Granted, that may be overdoing it book has rejuvenated this procedure parachute with a cable at hand that in the back-up department, even for worldwide, and with it, celestial navi- would release the entire side of the a prudent mariner, but there is no gation in general. plane with a single pull. It was a dif- doubt that your routine cel nav will is a way to ferent kind of flying than I was used shine in the light of your new skills find your and to, and it made me a better pilot. as a “lunarian,” with skills that can using a sextant to measure the The aerobatics of celestial navi- be mastered sitting in a chair in your angular heights of celestial bodies gation is called “the lunar distance backyard, without a view of the sea above the . It has been used method for finding longitude with- horizon. Lunar skills are universally by mariners at sea and explorers on out time,” or “lunars” for short. And considered the hallmark of the best land for 300 years, and is still used now the instructor is saying that if celestial . as a dependable backup to modern you learn lunars, you will become electronic navigation. You cannot get a far better celestial navigator in THE REJUVENATION OF CEL NAV an Unlimited Ocean Masters license your routine work. On top of that, The opportunity to carry out this from the USCG without knowing

22 Blue Water Sailing • August 2010 routine celestial navigation. Routine celestial navigation relies upon accurate time (Universal Time) to find the longitude of a position (latitude does not require time). Ad- The circles the earth (360°) in about 30 days, so viewed at vanced celestial navigators, however, the same time each night, it moves eastward through the at can find longitude without knowing a rate of about 12°/day. The moon’s path runs through the stars of the time using the technique of Lu- the Zodiac. Drawing from Emergency Navigation by David Burch nar Distance. In this technique, the sextant is used to measure the angu- lar distance between the moon and another celestial body along its path. ed out by the early 1800s, but they BEYOND NORMAL Since this distance slowly changes were still very expensive, especially With good timekeeping practice, as the moon moves eastward though since one was not enough to guaran- we should not lose accurate time in the Zodiac , it can be tee the right time. If it is wrong, you normal conditions, especially since used to find the time of day that is don’t know it. Likewise, two are not we have accurate time from every needed to complete the longitude enough. To know the time accurate GPS satellite, and there are numer- determination. to the second, over a long voyage ous radio broadcasts of GMT, now There are several reasons this away from civilization, you need at called Universal Time (UT). But it is valuable technique has not been least three . This is still true not unheard of, and prudent sea- part of routine celestial navigation if you want to be independent of manship means considering things for over 100 years. First and fore- radios and GPS. beyond normal conditions. most, it is not needed as long as the I say “,” meaning a portable All electronics are vulnerable at navigator has accurate time, which , but I should say “chronom- sea. Watchbands are more vulner- is readily at hand these days. The eter.” A chronometer is just a watch able than watches in many cases, history of lunars is inseparable from that gains or loses time at a constant which can lead to the loss of a watch. the history of timekeeping at sea, rate. The actual magnitude of the Plus they take batteries. Do you because the achievements in astrono- rate does not matter, so long as it is know how long your watch battery my needed to predict the location of constant. With a known constant will last? Do you take spare batteries the moon accurate enough for lunars rate and date set, you can always when you go offshore? If your watch came about at almost the same time figure the correct time. By the mid- stops with a dead battery and you as the invention of accurate seago- to late-1800s, chronometers, though replace it offshore, what time do you ing watches—the mid 1700s. It is a still expensive, were in reach of set it back to? Does this turn your famous story, made popular in Dava most ship’s captains. Chronometers three chronometers into two? Sobel’s book Longitude—a boon to the remained relatively expensive up And, there is always Doomsday. public knowledge of navigation his- to the days of the Bulova Accutron Those of us who thought Doomsday tory, despite some poetic license and in the early 1960s, then the prices was somehow more remote after the struggle with details. But the invention started down. Now, essentially any fall of the Soviet Union are waking alone did not make it a practical solu- quartz watch is a chronometer, and up to smell the coffee. The world tion. It needed testing (Captain Cook three top-notch, waterproof models has not evolved as we might have did some of this), and most crucially, it are less than $100. But they still have guessed it would. Two days ago, one had to be proven that someone other to be tested, preferably over the full nuclear power literally threatened a than the inventor () temperature range expected. Put neighbor with total destruction after could manufacture them. them inside an electric blanket and torpedoing one of its ships and kill- The production and dependability then inside a fridge for a couple of ing 48 sailors. The concept of nuclear of the instruments was getting sort- as you monitor their rates. proliferation and its dire conse- www.bwsailing.com 23 nce r Dista Luna curacy is about the conventional procedure using +/-+ 0.1’ of arc. the horizon. Plus, it contains a self- Without much consistency check because it mea- practice or sures the ’s semi-diameter, which good instruc- can be looked up in the . tion, navigators This correction measurement is not might average taught in modern textbooks that do three or four not include lunars. that The other issue has been the chal- H1 H2 limit, or even lenge of analyzing the lunar distance a bit worse. To to get longitude once it has been be successful measured accurately. The govern- with lunars, ment tables that used to do this went however, you out of print in the early 1900s and it must practice is essentially impossible to use old until you can ones for modern sights. There are “Lunar distance” is the angle between the edge of the approach the computer programs and Internet moon and another celestial body along the Zodiac. The instrument sites that have computed the solu- sextant can reach out to almost 120°, though sights half this range or less are easier. The angular heights of limit routinely, tions for many years, but reliance on the bodies perpendicular to the horizon are used in the even using the a computer or an Internet service for analysis, but these values can be computed if an almanac sextant in the a back up procedure is completely in- is available. See www.historicalatlas.com/lunars for lunar awkward di- congruous. Thus, there has not been computations and data. Drawing from Celestial Naviga- agonal manner. a logical role for lunars outside of tion by David Burch Higher-powered academic and historic study beyond monocular a select group of sextant experts who quences are more and more a part of telescopes help with this. Precomput- use it to maintain their prowess. the daily news, not less. It is way too ing the lunar distance ahead of time That is, until now. early to write off Doom. is also helpful. There are navigators who do AN INGENIOUS APPLICATION WHAT YOU DON’T KNOW… lunars with plastic , but this The Stark Tables are a modern The main reason most navigators takes even more special care, and take on this venerable problem, but do not use lunars is because they do average results are not as good as as lunar expert George Huxtable, not need to; that is, if we rule out the with metal sextants. Put another FRIN, put it, “Captain Cook would even bigger reason—most naviga- way, it would make you even better have relished using the Stark Tables, tors are unaware that the technique if you could do them with plastic had they been available to him then.” exists because it was not covered in sextants, and in any event it is a way They are an ingenious application any books they used. to see how the whole process works of the same basic methods of the Navigators who are aware of without the investment of a metal 1700s, but easier to use. Doing all lunars and would like to learn them sextant. The author’s booklet How to the paperwork by hand, filling out have other challenges. First, the spe- Use Plastic Sextants (starpath.com) is custom forms, you can go from cial diagonal sextant sights are more required reading for this endeavor, a measured lunar distance to the difficult than normal cel nav sights, besides raising the general quality of correct time and your longitude in which are always measured straight all sextant sights, metal and plastic. about 15 minutes, without needing up from the horizon, and the results As an aside to celestial navigators, a calculator. You can measure the must be more accurate. This requires another great benefit is that you will lunar distance any time of night that learning to use the sextant to its very learn a new technique for finding is convenient, since you do not need limits. But this challenge is part of the sextant’s index correction (what to see the horizon. The altitudes of the reward. we call at Starpath the solar method). the bodies above the horizon (which The practical limit to sextant ac- This is much more accurate than cannot be seen in the middle of the

24 Blue Water Sailing • August 2010