NavList:

I was really surprised to see my name among the authors of the recent posts in NavList, because I have not posted anything lately. Only after reading the top note, which was added by the host of NavList – Frank, it became clear that the reason of reposting this 4 years old message is the post made by Paul Quincey, which was an answer to my old post.

Dear Paul,

Thanks for your comments.

About 4 years ago I only started to study the early lunar clearing methods. Now I have more information than back then. Of course, now I am familiar with J. Harrison’s observations on board “Dolphin”.  I found the publications of all his observations during “Dolphin” vayage. I have recalculated one set using the Mariner’s Guide metodology.

I have found N. Maskelyne’s original lunar calculations in his notebooks, which are publicly available in the net. And I have recalculated (using the Mariner’s Guide method) several of Maskelynes observations with exclusive opportunity to compare almost every intermediate calculation step.

I have found also full lunar calculations  made on board HMS “Providence” in 1763 (this is also prealmanac era), and recalculated them in the same maner.

I highly appreciate the work of all these early lunar calculations and I share the respectful assessement of the astronomer W. Wales who wrote in 1788 about the observations made on board “Dolphin” :

"The lunar observations which were made on board the Dolphin, in her second voyage, under the command of Captain Wallis, were all made by Mr, Harrison, the Purser: they were also computed by him; and it is but justice to his merit to say that they have every apperance of being exceeding good ones. It is also much to his credit as an astronomer, that I have found but one error of any importance in all his computations, notwithstanding he had not the advantage of a Nautical Almanac, but had all the places of the sun and moon to compute from the tables. Computing these observations was, at that time, an arduous task in comparision of what it is now! The observations were made with a bras Hadley’s Sextant of 18 inches radius, supported on the back with edge bars, and made by the late Mr. Bird."

Modris F