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Subject: Re: Lunar distances
From: Eric Haberfellner (ehaberfe@XXX.XXX)
Date: Sat Jan 26 2002 - 01:38:06 EST
I am not an expert on Lunars, but I believe that Lechter gives a complete
solution. He states:
"In discovering a way to solve it [GMT by lunar distance] using only the
Nautical Almanac and the ordinary sight reduction tables I had on board
(H.O. 214), I experienced one of the great intellectual triumphs of my life.
On the 25th day of the passage, with 500 miles to go, I was able to prove
beyond all doubt that my clock was correct, within one minute of GMT, so my
longitude was gound within 30 miles or so - ample precision for the upcoming
landfall"
This was in 1963. Did the Nautical Almanac still have Lunar distance tables
at that time? I will have to dig into this material to figure out what
information he actually uses from the Nautical Almanac. I don't have time
right now.
He has some equations, and gives complete examples.
Eric Haberfellner
-----Original Message-----
From: Navigation Mailing List
[mailto:NAVIGATION-L@XXX.XXX]On Behalf Of Chuck Griffiths
Sent: Friday, January 25, 2002 12:09 PM
To: NAVIGATION-L@XXX.XXX
Subject: Re: Lunar distances
george@XXX.XXX wrote:
...There's no escaping the fact that lunar distances are a complex business.
If
there existed accessible textbooks on the subject, I could have simply
referred the reader to those. The only modern one I am familiar with is
C.H.Cotter, "A History of Nautical Astronomy" (London, 1968), which is very
hard to find.
If any reader knows of other useful textbooks on lunars, please say. Eric
Haberfellner tells me of "Self-Contained Celestial Navigation with H.O.
208" by John S. Letcher, Jr., published by International Marine Publishing
Company in 1977.
He says- "This book (to my suprise) has a chapter on "Time by Lunar
Distance" and a chapter on "Time by Lunar Lines of Position". This would
make it one of the few "modern" books that deals with this subject."...
Which brings to mind the following:
I'm curious whether anyone has an old enough edition of Bowditch to still
have
tables for clearing lunar distances. I believe that the tables and
explanations
were included until the mid-60's. What did these tables provide solutions
for?
My related question: Has anyone cataloged the tables and articles that have
been
removed from Bowditch over the years? I have to say, the 1995 edition,
compared
to the 1977 edition, seems to have left out a lot of good information e.g.,
correct plotting of high angle sights and the history of sight reduction
techniques. If you start adding up just the few things that I'm aware of
that
have been taken out over the years - tables for clearing lunar distances,
Ageton's tables, better explanations spherical trig, it seems like a
collection
of the "lost" Bowditch articles and tables would be a pretty nice reference
to
own.
Chuck Griffiths
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