NavList:

Thanks, Wolfgang! That's lots of useful detail.

You wrote that longitude "became a hot topic between Portugal and Spain in the early 16th century when Portuguese navigators reached the fabled Spice Island in 1512."

It's a fascinating thing, right? Papal bulls, "international" negotiations, and imaginary power founded on distances and hypothetical longitudes which could barely be measured... Fussing over the niceties of a diplomatic treaty seemingly dividing the world cleanly and surgically... on the eve of developments that would make that division mostly irrelevant and quaint (except of course, in South America). And yet even the Dutch who controlled much of Indonesia for centuries paid at least small "homage" to the treaties (Zaragoza and less directly Tordesillas) leaving the dividing line on New Guinea, nearly the modern border even today, rather close to the old plan.

You added:
"The Magellan voyage therefore not only had the aim of finding a west route to the Indies - thereby avoiding the Portuguese realm - but also to find out the position of the Spice Islands."

Was this explicitly stated in some sense? It's implied, of course, especially with retrospect, but was there some understanding that the Spice Islands could be up for grabs if Magellan et al. could prove their longitude was on the other side of the line? I have to wonder how much weight would have been given by those 16th century Spanish and Portuguese negotiators to such problematic attempts to measure longitude on the opposite side of the globe! Was it all just for show?

You continued:
"In the preparations for the voyage Francisco and Ruy Faleiro proposed the method that Andres de San Marin apparently used in his observations and calculations (it was also explained in Faleiro's "Tratado del Esphera y delarte del marear" published in 1535 and in appendix to Pigafetta's narrative of the voyage). A similar method was proposed by Anthony Linton in 1609 and probably used by William Baffin in 1612."

Fascinating. Thanks. Is there any modern account of the astronomical and mathematical details of the method they proposed (disclaimer: for all I know, this is all explained in the article by Gaspar ...still haven't read it!). I was aware of Baffin's attempt at lunars, and there were a few others. Apart from the problem with a theory of the Moon (which, if anyone had realized it, could have been bypassed by careful, regular --ideally relatively simultaneous-- observations of the Moon in the home longitude) and the lack of adequate instruments, in the examples I've seen there was also some considerable confusion over the problem of accurate local time, which is also critical to any astronomical longitude observations. Is there any moden account of Faleiro's methodology that deals with all of this?

You wrote:
"Nonetheless Andres de San Martin's measurements were not simply guesswork but an attempt to use astronomical knowledge in a stringent way."

Yes, I gathered that, and they're absolutely interesting footnotes, worthy of attention, in the history of navigation. Even though the experiments didn't work and could not have worked even with great attention to detail, they constitude "ground proof" that the method of lunars was understood in principle and ready to be applied in practice centuries before the details were all worked out.

And you added:
"And, by the way, as so often Wikipedia is wrong in historical detail (at least regarding the history of navigation): there is no evidance that Elcano owned books on astronomy. "

Yes, it's what I call (in my own musings) the "Low N" problem. Wikipedia's in-house teams probably have a nice long descriptive title for it and an acronym for it, too :). The "N" in my account is the number of authors/editors "actively maintaining" any given Wikipedia article. Many Wikipedia articles are excellent. Yet many have significant flaws and systematic biases. There is some critical level for N that I estimate to be between ten and one hundred contributing authors that usually results in a reliable, useful article, so long as those authors are not collectively all part of some distinct advocacy community. Good articles have big crowds of authors/editors who are mostly independent and frequently competitive. That usually works. If N is below that level, in the "Low N" regime, articles tend to suffer from the problems that led to the original poor reputation of Wikipedia dating back to its origins, now nearly two decades ago for some articles. Low quality articles have few contributors. They suffer from the "Low N" disease.

Wolfgang, do you have a list, even just an informal one "in your head", of pre-modern (let's say pre-1760) attempts at lunar-derived longitudes?

Frank Reed