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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

   

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