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George;
There is a passing reference to the faults in the Nautical Almanac etc in:-
"The Almanacs, Yesterday, Today and Tomorrow by Seidelmann.PM et. al."
which is item 60 in the index of "The Journal of the Institute of
Navigation" disk. I believe you have a copy of this.

Clive.



----- Original Message -----
From: "George Huxtable" 
To: 
Sent: Monday, March 03, 2008 10:59 AM
Subject: [NavList 4573] Flinders' Survey of Australia.


>
> I've just been reading "The Voyage of the Investigator", by K A Austin,
> written in 1964. This is the story of Matthew Flinders' cicumnavigation
> and
> survey of the continent of Australia from 1801 to 1803.
>
> It's rather short on the technical detail that I like to go for, but
> nevertheless a good account of an important voyage, by a skilled and
> enterprising (if unfortunate) navigator.
>
> Flinders died at only 40, in 1814, and the last few years of his life were
> spent in writing "A Voyage to Terra Australis", in two volumes and a folio
> Atlas, which appeared in the year he died.
>
> On page 202, Austin writes-
>
> "A major setback occurred when the lunar tables that had been used during
> the voyage were found tohave been erroneous. As a result, all observations
> made for longitude had to be corrected, and all charts altered
> accordingly.
> This revision took up most of 1813".
>
> [Unfortunately, no reference is given for that interesting bit of
> information. Perhaps it's mentioned within the journal itself, which I
> haven't read. Can anyone tell me if an accessible digitised version of
> Flinders' "A Voyage to Terra Australis" exists? All I have is an edition
> (2000) by Tim Flannery, titled "Terra Australis", purporting to be of
> Flinders' book, but so thoroughly filleted that little remains.]
>
> It's a bit of a surprise, in that Austin also tells us, on page 44, that
> the
> Board of Longitude provided Investigator with "astronomical telescopes and
> five timekeepers". The chronometers of that era were not always robust,
> and
> it's likely that not all the five remained in action over the whole two
> years.
>
> However, the problem with chronometers in those days (and later) was their
> gradual drift. Fine for on ocean voyage of a couple of months, but
> providing
> unacceptably degraded longitudes when used over much longer periods than
> that, unless some known headland, with known longitude, had been sighted
> en
> route. Flinders had left civilisation (if Port Jackson, later known as
> Sydney, could be described that way) in May 1802,. From what Austin tells
> us, it appears that from then on he must have relied on his lunars to find
> any drift. That was exactly what Cook had had to do in his second voyage,
> using an early chronometer, 30 years before. Neither Cook nor Flinders
> could
> expect to do any better than the precision of the lunar predictions in
> their
> current Almanacs.
>
> I have read comments elsewhere about inaccuracies in the Nautical Almanac,
> which appears not to have progressed much in prediction accuracy since its
> inception in 1767, and grown complacent about it. I wonder how big were
> those almanac errors in 1801-03, and who or what had brought them to light
> by 1813? It's an interesting thought, that if those discovered Almanac
> errors were large enough to call for significant corrections to Flinders'
> observed longitudes, they were affecting every other lunar navigator,
> elsewhere in the World, in exactly the same way.
>
> George.
>
> contact George Huxtable at george@huxtable.u-net.com
> or at +44 1865 820222 (from UK, 01865 820222)
> or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
>
>
> >
>
>
>
> --
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>



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