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    Re: Flinders' Survey of Australia.
    From: Clive Sutherland
    Date: 2008 Mar 3, 15:47 -0000

    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.
    ----- Original Message -----
    From: "George Huxtable" 
    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.
    > >
    > --
    > No virus found in this incoming message.
    > Checked by AVG Free Edition.
    > Version: 7.5.516 / Virus Database: 269.21.3/1306 - Release Date:
    > 01/03/2008 17:41
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