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Dear List,

I doubt that George will be satisfied with this, but it is as close as I
could come in the time I allotted.

Here is a link that describes in great detail the origin and history of the
"Nautical Day" as conceived by the British based on Cook's voyages. It may,
or may not be the answer looked for.

http://www.aandc.org/research/nautical_time_and_date.html

Source:  P.O. Box 125, Picton, Ontario, K0K 2T0, Canada
      Phone 1 613 476 1177 -  Fax 1 613 476 7598


I would like to add my own.

The seagoing Navigator's day begins about 20 min before the commencement of
AM Nautical Twilight, and ends maybe 20 min, after the end of evening
Nautical Twilight. After both periods he may spend 1/2 to 1 hr reducing and
plotting his round of sights to arrive at his FIX.

Please remember, I said it was my own concept of a Nautical Day.

Joel Jacobs


----- Original Message -----
From: "George Huxtable" 
To: 
Sent: Friday, February 06, 2004 3:01 PM
Subject: The Nautical Day


> I've recently been reading "The Arctic Whaling Journals of William
Scoresby
> the Younger, vol 1." ed. C. Ian Jackson, pub. The Hakluyt Society 2003.
> This covers his first three voyages as master, in 1811, 1812, and 1813.
> Scoresby made 12 such voyages, and it is intended that future volumes will
> cover the rest.
>
> Scoresby was involved in the "Greenland Whaling", which took place each
> year to the East of Greenland, near to the Western coast of Spitzbergen.
>
> While in port, and when making his way out to sea, Scoresby's journal was
> written up according to the calendar day, as we're all familiar with,
> starting at ending at midnight.
>
> Most of us are aware that until the 1920s, time in the Nautical Almanac
was
> in terms of the Astronomical Day, which started at the noon of the
calendar
> day having the same date. The Astronomical Day was therefore 12 hours
after
> the corresponding calendar day.
>
> However, as soon as Scoresby had got to sea, he started to write his
> journal (which was effectively his log) according to a different timescale
> altogether, the Nautical Day. This started and ended at the noon PRECEDING
> the calendar day with the same date.
>
> I had heard of the Nautical Day before, but the only reference to it I
have
> been able to find is in Bowditch vol 2 (1981) in which he says-
>
> "Nautical Day- Until January 1, 1925, a day that began at noon, 12  hours
> earlier than the calendar day, or 24 hours earlier than the astronomical
> day of the same date."
>
> I had dismissed the Nautical Day as something of an early American
> aberration, but Scoresby has shown me that view was wrong.
>
> So why on Earth would mariners use yet another timescale, differing from
> both civil time and astronomical time? Were some almanacs, perhaps,
printed
> with Nautical Time as their argument? How prevalent was this use of
> Nautical Time, how far back did it go, when in practice did it end? Was it
> common within the whaling community generally?
>
> In the 18th century voyages of exploration I have read, I don't remember
> seeing any references to Nautical Time at all. So it doesn't seem to have
> been part of the exploring navigator's baggage, in the half-century
> preceding Scoresby.
>
> Can anyone offer any light on this matter, or provide any references that
> mention it?
>
> George.
>
> ================================================================
> contact George Huxtable by email at george@huxtable.u-net.com, by phone at
> 01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy
> Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
> ================================================================
>

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