NavList:

Modris, you wrote:
"It is really strange. There are enough evidence that J.Cook himself practiced lunar observations during the “Endeavour” voyage. And this was done also before 28. november, 1768."

But I think Green, the astronomer, was describing the state of the team's knowledge when he first came aboard, in the late summer of 1768. Even though the Nautical Almanac had been available from January 1767, he was surprised that it had not immediately converted every ocean-going mariner into a lunarian. But of course Cook was an eager and willing student and happy to learn from Green. There was plenty of time to learn the method on the voyage before even entering the Pacific, wasn't there? When Green penned this letter in November of 1768, I believe he was describing his impression a few months earlier. That's a consistent reading, isn't it?

Modris, you continued:
"And now about Lunars and Newfoundland. This is period before nautical almanac was published. Even assuming Cook practised Lunars, if he blindly relied on the results obtained from lunar observations, his maps would be much less accurate, because the accuracy of lunars is significantly lower than the accuracy of his survey methods. The reference points thus obtained are too inaccurate for dimensions of such an island as Newfoundland. If the reference points are in error of, say 1 degree, than all the coastline would be inaccurate.
To get more or less reliable reference points from Lunars, he would have to make hundreds of observations from one position (as it was typically done during his and other explorer’s expeditions) and calculate all these observations by the above mentioned long method. And even if he had done it, the results would be less accurate than methods he practiced."

Consider this... He didn't have to calculate a single one! He could have simply brought the observations home, if he had skill enough to make the observations properly (which I don't think he did before the Endeavour voyage, but just speaking hypothetically, there was no requirement to analyze them on-site). Also, he certainly did not need hundreds of observations. The way out of this is a method of using lunars for surveying/mapping/exploration which could have been practiced at a much earlier date, before the Nautical Almanac, before Mayer's all-important Moon tables, and before Maskelyne's own "British Mariners Guide"... certainly as early as 1750, but unfortunately the method was ignored in practice. If we have no reliable predictive model of the Moon's motion or if the model does not meet our standards, then we can use the Moon as our computer ...and work out the longitudes after all observations have been collected. This is not so different from the recent re-analysis of the lunar occultations made by Worsley during the "Endurance" voyage/shipwreck near Antarctica over a century after Cook [the analysis by NavList regulars Lars Bergman, Robin Stuart, and others]. The occultations of stars provided very good longitude based on an excellent but slightly stale lunar model. The plan, finally realized just a few years ago, was to compare the observations with the same or similar occultations made simultaneously at home. Small corrections can be applied based on the Moon's true motion that convert those "very good" longitudes into excellent longitudes.

How would this work with lunars? One observer travels to a distant part of the globe, maybe Newfoundland or possibly Polynesia. Lunars are shot at various locations, key islands or points on a larger landmass. Also required (and sometimes overlooked!) are high-quality observations for local apparent time (or local sidereal time; either will do) made simultaneously. Meanwhile, at home, observers are tasked to observe lunars at known locations (in and near Greenwich) each and every day at every possible hour when weather permits. Those latter observations are "cleared" to yield true or "geocentric" lunars. When the first observer returns from that distant corner of the globe, the lunars are worked to yield true distances, and those can be compared directly with the locally observed distances. GMT (or GAT) follows directly. And of course the rest, to get longitude, is easy. The difference between Greenwich time and local time is the longitude in time units. Convert to degrees (and even that, only if desired), and you're done. The Moon does the work -- it creates the exacting tables of lunar distances that we need to get the job done.

You concluded:
"And we must not forget that Cook was an expert in surveying the coasts. Methods he used are known and published "

Yes exactly! :) And note, too, that much of Newfoundland is well-suited for coastal surveying work. There are many wide bays and "notches" in the coast. One can "get in there" and see significant landmarks on widely spaced angular separations. And finally, let's not forget that latitude was easy, even then. Constructing a relatively detailed, accurate chart of the island of Newfoundland was not difficult, not in principle. It was, however, time-consuming work requiring painstaking attention to detail and proper methodology. The lack of a reliable overall longitude did not change the shape of the land, the complex "polygon" generated by the survey work, but it did change the final east-west position of that big polygon on the chart. Fortunately for later mariners, the overall longitude was not much in error.

Frank Reed