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From: Peter Fogg (no email)
Date: Fri Sep 05 2003 - 18:47:32 EDT
----- Original Message -----
From: "George Huxtable"
To those of us who have
> done all that introductory stuff, years ago, some of the fine-points and
> abstruse-topics and historical-questions are of great interest, and the
> Nav-L list is our method of communicating with each other about it. Would
> Peter Fogg deny us that?
No. And I enjoy them myself. Don't miss the point.
As for the Azimuth Tables, there are instructions in the book to be followed
to deal with the potential problems when the bearing is close to 90 or 270
degrees. A common sense approach, remembering that the whole idea is to
keep things simple on-board, is to give the tables a miss and use another
method (provided) in these rare enough cases. There is no need to make a
mountain out of a molehill. To say they are 'VERY bad' is a gross
exaggeration, at the VERY worse they might be only slightly naughty.
When taking sights the hand bearing compass is around my neck, and the
compass bearing of the star or planet noted with the other data (I might
need the corrected [true] bearing or azimuth to find out which body it is,
through the Prediction and Identification Tables). This corrected compass
bearing is accurate enough to use for plotting a sight, being out by a
degree or two makes little enough difference to the LOPs, and thus the fix,
in most cases. So the Azimuth Tables or the Weir Diagrams are mainly useful
as a checking tool.
Working the other way, knowing the azimuth accurately, is useful to check
for compass deviation, the particular effects of each individual boat that
alter the compass reading.
The advantages, in most cases, of having simple 'look up' tables immediately
providing an azimuth accurate enough for the purpose more than outweighs
any theoretical shortcoming they may have in some extreme example.
So with a common sense and practical approach one can approach the Azimuth
Tables with calm and confidence. Its a bit of a non-issue.
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