NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Patrick Goold
Date: 2011 Mar 28, 11:33 -0400
Many thanks for this! I believe I am getting the picture. 1767 is the revolutionary moment, the first Maskelyne almanac and the tables requisite. Before that Maskelyne's method seems to have been beyond even a captain of the quality of Wallis. According to Beaglehole Wallis noted on 20 August 1766 that his purser had determined the exact position, including longitude, of King George's Island "taking the Distance of the Sun from the Moon and Working it according to Dr. Masculines Method which we did not understand." Cook in his voyages in the Grenville is latitude sailing, determining his longitude by dead reckoning. It is on the Endeavor that he learns the use of the almanac and tables. "By the last year of these Atlantic voyages, in 1767, the new Nautical Almanac appeared, making it practicable for mariners to determine longitude by lunar distance; a technique Cook was to learn in 1768, aboard Endeavour" (George Huxtable and Ian Jackson).
What makes Maskelyne's method impractical? It seems it could give good answers. Is it just the complexity of the calculations required? Did Maskelyne's 'computers' follow his method or some other?
Patrick
Patrick, you wrote:
"Looking for a nav guide contemporaneous with Cook, I found a copy Maskelyne's "British Mariner's Guide: Containing complete and easy instructions for the discovery of the longitude at sea and land". My question is, is Maskelyne's method similar to what Cook was using? The astronomer royal has not appeared so far in B's account except as a name. Did Cook know of his work and did he use it?"The "British Mariner's Guide" published in 1763 was a stopgap with quite long and elaborate calculations which, while feasible with great effort, were not really a practical solution, and Maskelyne knew it. He campaigned in the next few years to have the calculations greatly reduced for practical navigation at sea by doing most of the computations on land. He made his case and got his funds; the longitude would be found by tabulating lunar distances in a little book, pre-computed in Britain, for use all around the globe. THIS was the origin of the original "Nautical Almanac and Astronomical Ephemeris" which is the ancestor of our modern "Nautical Almanac".
The first Nautical Almanacs were published with data for the year 1767, and they were cranked out rather quickly by Maskelyne's team of computers (a "computer" was a person). When James Cook and Joseph Banks and the others left for the Pacific to observe the transit of Venus, they had the Nautical Almanac available for several years ahead. I don't remember if they had enough editions for the whole duration of that first voyage.
Cook's expedition also had the "Tables Requisite" which included all the other details for accomplishing the job including instructions on clearing lunar distances and working all the other calculations of nautical astronomy. You can find two editions of the Tables Requisite (made available by Google Books) under the "Resources" section right on the main NavList page. Here's the short link to this list of books (which I try to maintain): http://www.fer3.com/arc/navbooks2.html
-FER
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--
Dr. Patrick Goold
Department of Philosophy
Virginia Wesleyan College
Norfolk, VA 23502
757 455 3357
Charles Olson: "Love the World -- and stay inside it."
