NavList:

Roger Sinnott, a few days ago, you wrote:
"I think every navigator should know something about lunars, in case the unthinkable emergency arises."

And you mentioned the story of the whaleship Essex. If not the survivors of the Essex specifically, there were many other cases where time, money, and lives were lost due to uncertain longitude. Lunars were the solution! Certainly that was a valid argument 200 years ago, but it's worth noting that this value was declining already, even when the Essex was shipwrecked. Although "sea clocks" or "time keepers" or "chronometers" (as they were known after c.1810) were the better answer to the problem of keeping Greenwich time at sea, their extreme scarcity and correspondingly high price made them inaccessible in some backwaters of maritime culture --like New England in the early part of the 19th century. Lunars became quite popular in the New England whaling fleet and were an enabling technology for American dominance of the eastern half of the Pacific Ocean for decades in the 19th century. There are many references to lunars in the logbooks back then, and there's still plenty to be learned about the practice by sieving those resources.

The time for lunars was limited. After c.1835 they were primarily used as a check on a single, troublesome chronometer. Aboard the Charles W. Morgan (the last New England whaleship, preserved at Mystic Seaport) lunars were worked occasionally on the maiden voyage in the early 1840s. But after c.1850 they nearly disappear from the logbooks. It's an almost complete transition. The check on the chronometer in later decades was, not lunars, but yet another chronometer ...or two or three or more. Even a poorly-equipped ocean-going vessel late in the century would usually carry two chronometers to serve as tests against each other. Navigators had learned that the error that might be estimated by observing an ensemble of chronometers, as the time they displayed gradually drifted away from one another over weeks at sea, was just as good as an autonomous check on time derived from the Moon's position. Three chronometers beats a dozen lunars.

By 1883, Lecky in his "Wrinkles in Practical Navigation" was surely correct, and speaking from his own lifetime of experience, when he described lunars as being "as dead as Julius Caesar" and "never to be resurrectionized". We can forgive him for not imagining an entirely new way of employing lunar distance observations, not for time but for trajectory correction, on the Apollo missions to the Moon almost a century later. At sea, though, they were no longer of significant practical value. At the same time, it's also true that no navigational practice ever really dies out unless there's some vital information or broadcast data that ceases to be published, which was never strictly a problem for would-be lunarians, and small numbers of navigators continued to experiment with lunars and, yes, "play" with lunars in every decade through the 20th century and on to the present. 

Do we need lunars? Should a prudent celestial navigator keep them as a significant component in a suite of tools? No. To that I would say, definitely not. Lunars are fun. They're interesting and challenging. They help us refine our skills and test our sextants to the limit, but they serve no critical purpose. No one in the modern world loses Greenwich Time. As recently as 1995, not one celestial navigator in a hundred knew more about lunars than the name, and not one in ten thousand had ever done the work --even experimentally-- to use them in practice. Today those fractions are both perhaps bumped up by a factor of ten. It's hard to say though whether the total number of people who can do lunars is higher today than it was twenty years ago since the total number of navigators with functional skills in celestial navigation has surely declined. One thing we can count on: it does seem likely though that the majority of those who do learn to love lunars... eventually make their way here to NavList.

As far as I know, there's only one class offered in the theory, history, and practice of lunars anywhere in the world, and that's the two-day class that I created and teach at Mystic Seaport. It's offered this Spring in Mystic on the weekend of April 21-22. Details on my website (address below).

Frank Reed
Clockwork Mapping / ReedNavigation.com
Conanicut Island USA