wrote in message
...
On Tue, 16 Nov 2004 11:34:01 +1300, "Mark" wrote:

Your post raises an interesting topic. The relation between the sun, a
compass and an analogue watch (or clock) is an equation. If you have any
two
of these three items, the third can be determined.

For example, if you can see the sun, and you are wearing an analogue
watch,
you can determine true North. Or, if you have a compass, and you can see
the
sun, you can determine what time it is.

This is far from exact, based on the equation of time, which
is not reflected on the watch. Local solar time, mean solar time and
zone time are all different from each other.


Yes, you're right, its far from exact. If you want it to be exact then
you'll need the compass after all. Oh, and if you want true North then
you'll need to know the magnetic variation at your current location. And to
help you know your current location, you'll need the compass.... etc. I
suppose I was outlining a rule of thumb, perhaps to be used in an emergency
situation, or simply as an exercise to demonstrate such relationships
between the three.


Remember, that it is a watch or clock that is used to determine longitude
also. First, you set your watch to midday exactly as the sun reaches the
highest point in the sky (Note: your watch is now set to sidereal time
and
not mean time).

Actually it's set to solar time. A solar day does not
correspond exactly to a sidereal day, so solar and siderial 00:00
drift with respect to each other.


Again, thanks for the correction. Better not rely on me if you get lost!

Anyway, after re-reading all of this, I realised I have drifted off-course
and off-topic. Now, back to the radio....

Mark.
Auckland, New Zealand, which is located at 36 degrees, 52 minutes South, 174
degrees, 52 minutes East. And the magnetic variation is currently around 19
degrees, 30 minutes East.