NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Update of www.LunarDistance.com
From: Arthur Pearson
Date: 2003 Sep 25, 18:12 -0400
From: Arthur Pearson
Date: 2003 Sep 25, 18:12 -0400
Ladies and Gentlemen: After a long season of distractions, I have been able to update www.LD-DEADLINK-com with several items that have been posted to our discussion group or forwarded to me over the summer. I apologize for falling behind in keeping the site current. I hope those of you who may have been similarly distracted can catch up with some very interesting new material. Simply visit the site and go to the Site Map for a guide to the following new articles and links. David Thomson's 1824 tables for clearing the Lunar Distance. Jan Kalivoda continues with his historical perspective on the development of methods for clearing the distance. Jan presents an introduction to David Thomson and his highly regarded set of tables. He then presents with commentary a rigorous piece by George Huxtable on the math and theory behind them. The article is available at http://members.verizon.net/~vze3nfrm/LunarsFiles/Thomson.pdf. Bruce Stark's Tables in historical perspective. Jan Kalivoda applies his historical perspective on the methods used to clear the lunar distance to Bruce's 1997 tables. Jan concludes that "They don't repeat old solutions mechanically, but are significantly better than renowned works of the past, although they don't misuse the modern technical possibilities and go the fully traditional way of tabular and paper solution. It had to be an intellectual adventure to compose them and it is a delight to study them." Visit http://www.i-DEADLINK-com/lists/navigation/0307/0122.html and you may agree with Jan "that with these Tables, the history of Lunar Distances is consummated now and the long line of rigorous methods for clearing them ends successfully - only in our days." Contents of Maskelyne's 1766 Tables Requisite In 1766, Nevil Maskelyne produced the first publications that made it practical for mariners to apply the lunar distance method for finding longitude at sea. First was his Nautical Almanac and Astronomical Ephemeris which among other data included pre-calculated lunar distances to five well selected bodies for every three hour interval of Greenwich time. The companion piece to the Almanac was Maskelyne's Tables Requisite to be Used with the Nautical Ephemeris for Finding the Latitude and Longitude at Sea. This volume contained 30 tables needed for correction of observations and calculation of latitude and longitude. In addition, it contained an explanation of the tables and 13 problems that illustrated the solution to various navigational situations. Bruce Stark has a copy of the Tables Requisite and kindly posted a full listing of all the tables and problems listed in its table of contents. The listing offers a wonderful insight into the systematic and thorough approach taken by Maskelyne in his historic breakthrough in the quest for accurate longitude at sea. The contents are posted in two parts at: http://www.i-DEADLINK-com/lists/navigation/0306/0012.html (Tables) http://www.i-DEADLINK-com/lists/navigation/0306/0013.html (Explanation and Problems) A Lunar Distance Calculation, Sir Augustus Charles Gregory, North Australian Expedition, 1855-56 by Kieran Kelly. A detailed analysis of the extraordinary work of A. C. Gregory during his surveys of Australia. This 63 page article is a testament to the skill and professionalism of a remarkable explorer. The analysis of Gregory's lunars demonstrates the amazing precision attained by true masters of the technique during the period of it's greatest relevance to geographical exploration. The article is available at http://users.bigpond.net.au/kjkelly/gregorylunar/A%20Lunar%20Distance%20 Calculation%20v1.pdf. The author also has posted a website with descriptions of his recent visit to Gregory National Park with photos and sketch maps of an area explored by Gregory in 1856. Anyone who wants a glimpse of the stark landscape surveyed by this pioneer should visit http://users.bigpond.net.au/kjkelly/. Best wishes to all, I continue to enjoy the discussions this community of navigators and hope to contribute more regularly in the future. Regards, Arthur