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    Re: Lunars in history
    From: Frank Reed
    Date: 2021 Jul 7, 17:49 -0700

    Tom Harnish, you wrote:
    "As a backyard astronomer and as a sailor the topic sounded interesting and I was curious why Murchie, who taught and practiced navigation for years, could be so wrong."

    He was wrong because he only knew the "lore" of the history of navigation, not the actual history. Fortunately we have mountains of primary source evidence to work from to dispel the lore: thousands of logbooks and journals written by practical navigators with their own pens. I draw directly on old logbooks and similar resources when I teach my workshops on "Celestial Navigation in the Age of Sail" (covering the non-lunar parts) and "Lunars: Finding Longitude by Lunar Distances". It's like peering right over the navigators shoulders as they worked their sights in different decades of the 19th century. 

    You wrote:
    "I stumbled on an old article by Littlehales"

    You've used a dangerous word in any study of history -- "old" :). That article you found is from 1909 which was decades after lunars had become largely obsolete at sea. That's not very "old" in the context of centuries of astronomical navigation history. Littlehales was describing the status of lunars at this very late date because, at long last, the editors of the various nautical almanacs around the world had seen the light by this time, and they were in the process of dropping the lunar distance tables from their pages. The excuses for conservatism had fallen away... These tables of pre-computed lunar distances had been found in nautical almanacs since 1767. From 1767 to 1909 is a span of over 140 years. And German nautical almanacs continued to include the tables for another decade bringing the total to a century and a half. Did they print those tables for magicians?? 

    You quoted Littlehales:
    "At sea the observation of a lunar distance requires great accuracy and skill, especially if there be much vibration in the vessel; and it is found that hardly one navigator in two hundred has ever carried out the calculation of a longitude by the lunar-distance method in practice."

    Again, it must be emphasized that he is describing the situation decades after lunars had already ceased to be useful. By 1909 I would even argue that his 1-in-200 was probably an exaggeration. By that late date I would believe one in two thousand. As for great "accuracy" and "skill", it's always amazing to see navigators with only average sextant skills shoot their first lunars. After a few quick trials, a great many navigators (easily 50% among those I have trained in lunars) get results that are accurate to better than half a minute of arc if they're using an appropriate sextant. One thing you can be certain of though -- no navigator is ever happy with their lunar results. Every navigator craves just a little better.

    By the way, there's a subtle detail in this quote from Littlehales that emphasizes how late it is in the history of navigation. He refers to vessels with "much vibration"... The ships he's thinking of are also much more prone to rolling, which is also a hindrance to lunars --at least for a navigator who doesn't have a strong stomach! They are steamships, of course! In his era, nearly all ocean trade was aboard "vibrating" vessels with engines. Ships under sail did not "vibrate" per se. Sure, they would quake and rumble a little as they strike a wave. They would also, advantageously, tend to stay heeled either to port or starboard under the action of the wind, quite unlike rolling steamships.

    You continued:
    "Then I discovered Lecky and Allingham who famously wrote lunars were, by about 1850, "deader than Julius Caesar" and Lecky himself who's quoted as saying, "... [t]he writer of these pages, during a long experience at sea in all manner of vessels [since the 1850s] ..., has not fallen in with a dozen men who had themselves taken Lunars, or even had seen them taken."

    Just to clarify a detail here, Allingham was not involved in this. He took over editing Lecky's "Wrinkles" after the latter died (and maybe a few years earlier since I assume this was an orderly transfer of the crown). Lecky wrote that famous paragraph in which he said lunars are "as dead as Julius Caesar" and "never to be resurrectonised". I can quote it from memory because I've used that quote in my workshops, classes, and public presentations for seventeen years. And Lecky knew what he was talking about. He was speaking from his personal, practical experience with other British mariners in 1883. In fact, on well-equipped British vessels lunars were apparently over with by about 1835 (it's not a hard date). But it's important to note that they lasted another two decades or so on less well-equipped vessels, especially American sailing ships.

    By the way, I notice here that you say that Lecky "famously" wrote about lunars. So you're being a wee bit disingenuous then. If you're completely new to lunars, as you claim, then you wouldn't say that he "famously" wrote this, would you?

    You added:
    "I think you can see why I'm confused when you say the method was a common practice."

    You've run into a problem that confounds and confuses many people who approach the topic of lunars from the wrong end (the "end" of lunars is the wrong end!). If you read accounts from 1900 or so, everyone says they're useless, a pain in the neck, too much trouble for what they're worth. Lunars had been in the dustbin for navigators at sea for decades by 1900. Nothing ever really dies out in history, so there were still rare cases of lunars at sea, but sometime around 1850 or 1860, they were really no longer of practical value. They were also available for a few years in a semi-practical form (much more arduous computations) before the first British Nautical Almanac in 1767. So if we stretch a little on the tail end and pick up a few years at the beginning, we've got just about a hundred years --a full century during which lunars were widely used in at least some significant sector of the global maritime culture. I don't normally stretch it that far and call it "about 80 years". Lunars were in common use at seas for about eighty years.

    I almost always include a section on the "Long Decline" in my workshops and presentations on lunars, and there are some interesting features to that period. First of all, lunars were actively used in land exploration during those decades after they stopped being used at sea. There are some famous examples of this. In addition, mathematically-inclined navigators and specialists in navigation mathematics continued to write about them in journal articles, which often atract the attenion of academic researchers who think that the history of navigation will be found in jounral articles. Those specialists in mathematics were making a mistake that would last for over a century. Math-y folks were convinced that lunars had faded into disuse because the mathematical methods for "clearing" lunars were too difficult, beyond the capabilities of uneducated practical navigators. These people were wrong. There was some variety in the techniques available, and some (less popular!) methods were difficult, but the clearing tools widely used were easy --yes, genuinely easy. There was no call to invent new methods, and contrary to the imaginings of their authors that they had "finally solved the problem of lunars, making them easy and quick for the common mariner" (a common refrain), they didn't make them "easy and quick for the common mariner" because they already were for anyone who cared to try.

    You wrote:
    "I'm also confused by why you discount Newton's association."

    He had almost nothing to do with lunars. Without his inverse-square law of gravitation, there would have been no lunars tables in the nautical almanac, but they weren't his lunars or his lunar tables by a long stretch. Of course we still talk about "Newtonian physics" even in vast portions of physics that Isaac Newton himself never examined, but that's a well-understood shorthand in physics. It doesn't apply at all to the history of lunars.

    You added:
    "The helpful Stark Tables didn't exist in the 40s"

    That's peculiar, too. You said you didn't know about lunars, but now you're talking about the "helpful" tables self-published by Bruce Stark in the late 1990s. What makes you think they're helpful?

    And then:
    "and the Nautical Almanac stopped publishing lunar distance tables in the early 1900s so trying to use the method in the '40s would seem to require some kind of potent magic, just as Murchie suggests."

    Wow. You're gonna end up tying yourself in knots defending Murchie's bullshit, but we can discuss the extent of that under that earlier thread. I shifted this discussion to "Lunars in history" since all of this is fundamentally irrelevant to Murchie's original comment.

    Frank Reed
    Clockwork Mapping / ReedNavigation.com
    Conanicut Island USA

    PS: I also fixed your name in earlier posts and references to them. Thank you for letting me know. I was hoping you had a brother named "Tik" and the two of you were founders of a certain well-known social media outfit. :) 

       
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