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The reality is that in todays Navy they are ringing the bells when noon
for their time zone is indicated on the GPS receiver. The watch has
already been relieved, (no later than 1145) and even though by
regulation the navigator or quartermaster is supposed to be observing
LAN (if the weather permits) it probably isn't happening on the majority
of ships.

-----Original Message-----
From: Navigation Mailing List
[mailto:NAVIGATION-L@LISTSERV.WEBKAHUNA.COM] On Behalf Of George
Huxtable
Sent: Sunday, December 07, 2003 19:33
To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM
Subject: Re: Master & Commander

Bruce Stark quotes the following statement from a friend-

"By this time the Navigator is observing the track of the sun.  At his
signal, the OOD instructs the Bo's'n's Mate of the Watch to strike 8
bells.
Thus an exact noon is noted by the ringing of the ship's bell and it is
dead accurate with a well trained bridge watch.  Sometimes this takes a
bit
of doing, but rather quickly they all get on to it and we can all set
our
wrist watches accurately."

I would like to take issue with the "exact" and "accurately" aspects of
this statement. Time may be determined that way accurately enough for
change-of-watch, but NOT for navigational purposes. No matter how
well-trained a bridge watch is, there's no way to determine the
moment-of-noon, to within several minutes, by observing at or near noon,
for (at least) two reasons.

1. The Sun is rising so slowly, near noon, then remaining stationary
with
imperceptible motion, then falling so slowly, that it just isn't humanly
possible to determine the moment-of-noon with any accuracy. Only by
determining an altitude before noon, then the same after noon, and
splitting the time-difference, can any accuracy be obtained.

2. Even then, that's only the moment of maximum altitude, not the moment
of
local apparent noon, which occurs at the time of meridian passage.
Between
the two, even on a sailing vessel, there can be a discrepancy of 5
minutes
or so, depending on the Northerly or Southerly component of the speed of
the vessel.

Sorry to reiterate what's been said several times before on this list,
by
me and by others.

In other respects, the message was of great interest, and I hope Bruce
can
persuade its author to join our list.

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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