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Subject: On finding azimuth
From: Peter Fogg (ffive@XXX.XXX)
Date: Sat May 03 2003 - 19:42:59 EDT
When I'm taking sights part of the equipment is the hand bearing compass
around my neck on its lanyard, and part of the procedure is noting the
compass bearing of the body.
*The first great advantage of doing this is that the corrected bearing
is accurate enough to be used as an azimuth for plotting purposes, but
there are others
* It helps to learn the night sky, as I am still slowly doing
* It means observations in the near future can be planned in advance,
you know just where to look
*When conditions are less than ideal and a body is quickly observed
without reference to its constellation (eg through a gap in the clouds)
knowing its azimuth is essential for identification
[This argument works in reverse - once you are sure of the body (and the
time) there are a variety of means available to calculate the azimuth]
*The azimuth is needed to enter the diagram which indicates the slope -
the rate of apparent rise or fall of the body against which multiple
observations of the same body can be compared
*By comparing the compass bearing with the later calculated azimuth the
difference indicates the local error - compass variation and deviation
for that bearing. Taking away the known variation from the difference
leaves the local deviation - again, it may only be accurate for that
bearing. When I sail on other people's boats its about the only
practical way to calculate the deviation.
Can anyone think of any others?
Anyhow, knowing the azimuth is the least of the challenge of PRACTICAL
on-board celestial navigation.
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