"Marty" wrote in message
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Wilbur Hubbard wrote:
"Charles Momsen" wrote in message
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"Bart" wrote in message
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On Oct 23, 9:48 pm, "Charles Momsen" wrote:
"Bart" wrote in message

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Aside from the Sun, when heavenly body is most
useful for determining your latitude? [1 pt]
The earth, then Polaris.
For the Northern Hemisphere, Polaris is quite
useful. How much does it vary from true
North?

It depends on the time of year.


Bwahahahhahahahahhahahahhahahahhah! Time of year has nothing to do with
where Polaris is seen in the sky. The Earth's axis of rotation is only
different with respect to the sun making for seasons, not to the plane of
the ecliptic. Duh! Now, had you said something about it depends upon in
which epoch you might have had a point because of something called
precession of the Earth's rotational axis.

I hope this helps.

http://image.gsfc.nasa.gov/poetry/ask/q1795.html


Well Neal, strictly speaking Charles is correct,, it is caused by parallax
error. Or more correctly, geocentric parallax, for Polaris it's about
0.007",,, not likely that you'd be able to measure it while at sea.


Ref: http://www.alcyone.de/SIT/mainstars/SIT000816.htm

Hope this helps.

Cheers
Martin


So, you are saying the parallax is seven thousandths of an arc second
depending upon where in her orbit around the sun the Earth happens to be
(time of year)? I'll give you that but that parallax is too small to make
any difference when shooting a Polaris angle. So, my contention that saying
it depends upon the time of year is dumb remains true. Momsen must be
getting senile in his dotage.

Wilbur Hubbard