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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Fw: Lat. and Lon at LAN
From: Dick Savage
Date: 2004 Jan 7, 23:05 -0800
From: Dick Savage
Date: 2004 Jan 7, 23:05 -0800
----- Original Message -----
From: Dick Savage
Sent: Wednesday, January 07, 2004 11:03 PM
Subject: Fw: Lat. and Lon at LAN
----- Original Message -----
From: Dick Savage
Sent: Wednesday, January 07, 2004 10:57 PM
Subject: Lat. and Lon at LAN
This is a slick trick to use in certain conditions
to find your lat. and long. on a moveing vessel at sea.Although the resulting
long. won't be as accurate as the lat. taken at LAN it does have its' uses for
reduceing a fix at LAN instead of just a Lat at LAN.It's a decent technique when
conditions are such after LAN that no sights can be taken.It can be used in
conjuction with a running fix from a previos LOP to improve the results of the
LAN sight.
This is posted mainly to show those unaware or
interested and its' accuracy or dependability can be debated ad nuesium but it
is a good way to find a pos. when conditions in the real world conspire against
you.
Use the techniques associated with finding zt of
LAN and takeing the noon sight.If the sight taker timed the noon sight within a
few secounds of LAN(the Sun appears to hang for 20-30 sec at LAN but still moves
in that time frame to greater than 180* or less than 360*)the sight taker has
the vessel's longitude.When reduceing the sight to find Lat. at LAN go into the
N.A. find the whole degree,min. and sec. of the GHA of the Sun at LAN.At LAN the
Sun is 180 or 360* depending on the dec. of the Sun and hemisphere the vessel is
in.The GHA of the Sun within a few secounds of time from LAN will equal the
vessel's longitude.
So if conditions are such that you then or in the
future need a fix and not just a lat. line and can't obtain one this will give a
passable result.
Doug
