Evan Gatehouse wrote:

Anybody have any experience using a Northern Hemisphere compass as far south
as say New Zealand? I *know* you're supposed to have a s. hemisphere
compass in an ideal world, but I'm wondering how much the card deflects i.e.
is it still useable, even if tilted.


First I ever heard of such a thing.

I can't believe it matters. A compass is a compass.

Now, if you want to talk about sundials, I can tell you there is a
difference. My birdbath was bought as a yard ornament. The wife
thought it was "cute", with a little sailboat in the middle, the
sail being the, waddaya call it, that casts a shadow on the sundial
markings around the brim.

It is made in Australia, I think, or Malaysia. The numbers are
reversed so that if the sail's shadow falls at 12:00 noon, then a
hour later, if falls on 11:00. Other than that, it keeps excellant
reciprocal time.

Now, that makes sense, since around here, there is much commotion
regarding getting horses in front of carts, etc, that sort of thing.

The pedestrians never notice, but it does set the tone for the yard.
We have 3 large trees, a white pine, a balsam fir, and a blue spruce
all crowded together fighting for space by the driveway, with a
bench huddled amongst them, a good place to ruminate while enjoying
the scent and early morning sun with a cup of tea. We call them the
Father, The holy Ghost, and the Son. I guess it's no wonder that we
got, by chance at the garden department of Kent's, a southern
hemisphere sundial to set nearby.

I just seems to fit, somehow.

It matters, but a southern hemisphere compass? Yuk, yuk, yuk!

Terry K

"Terry Spragg" wrote in message
...
Evan Gatehouse wrote:


First I ever heard of such a thing.

I can't believe it matters. A compass is a compass.

It is because the Earth's magnetic field is not spherical. It dips in as
you get closer to the poles. Compass cards are not accurate unless they are
level. From about lat 35 to 40 on up to the poles the needle tends to dip
downward as it tries to align itself with the magnetic flux. Good compass
cards are balanced to counteract this dip. When a compass set up for the
Northern hemisphere is in the Southern hemisphere the counterweight
accentuates the dip and vise versa..

First I ever heard of such a thing.


lots of thing you never heard of before, terry.

I can't believe it matters.

believe

A compass is a compass.


**IF** you understand them, that is true. obviously, terry, you don't. a
magnetic card compass for the northern hemisphere is funcitionally different
from one for the southern hemisphere.

On 23 Oct 2004 02:32:30 GMT, (JAXAshby) wrote:

a
magnetic card compass for the northern hemisphere is funcitionally different
from one for the southern hemisphere.

I knew I should have played the lottery the day JAX finally got
something right and explained it without sounding like Forrest Gump.

Point made, JAX, now stand down before you strain something.

R.

rhys wrote:


On 23 Oct 2004 02:32:30 GMT, (JAXAshby) wrote:


a
magnetic card compass for the northern hemisphere is funcitionally different

from one for the southern hemisphere.

I knew I should have played the lottery the day JAX finally got
something right and explained it without sounding like Forrest Gump.

Point made, JAX, now stand down before you strain something.

R.

ok, ok, ok.

So, it's been a long time since dippy compasses were discussed in my
presence. Please pardon my forgetting a subject so long disused.

So, if your 5Kbuck compass needs heart surgurey to keep it levelled
up with a north weight instead of a south weight, why not use your
pocket silva and give it enough tilt so it doesn't bind? I've
tried it now, and it seems to work just fine with a bit of a twist
on. Mind, I'm a dippy northerner, but we're not that far north, I
guess, nor that dippy, unlike some extant.

I don't usually bother with Jakz so I had to seek out the comment
regarding weighted compass cards.

It seems to me the amount of dip in the compass reading might be
some indication that you're way north, or you are passing over the
magnetic pole or something.

If I go all that far north or south, I will remember this gem: "A
cheap hand compass can be used where a millonaire's compass cannot."
Appropriate gear for the mission, eh?

I would also bring alernative nav devices, like homing pigeons,
odour samples, wave pattern transform almanacs, depth sounder, even
RDF, LORAN, pylorous, sextant, charts, or GPS, I guess.

Mind, dipping compasses would only be needed at extreme latitudes.

Who'da thunk? I guess crossing the equator means a major compass
replacement every time you cross the line, eh? Is that what the
shellbacks do while the nymphs are getting transsubstantiated?

Does this mean I can't trust my compass card inclinometer any more?

Vapour, right?

Terry K

"Terry Spragg" wrote in message
....
It matters, but a southern hemisphere compass? Yuk, yuk, yuk!


Come on Terry, you're not supposed to make jaxie look smart.

Compasses do indeed need to be adjusted for the Southern Hemisphere. Here's the
Ritchie comment:
http://www.ritchienavigation.com/ser...albalance.html

here's the actual map of inclination (known to mariners as "dip")
http://www.ngdc.noaa.gov/seg/geomag/icons/wmm2000i.gif
As you can see, there's a serious difference between the USA and New Zealand - plenty
to make the card jam if not balance properly.

Everything you might want to know about the Earth's magnetism:
http://www.ngdc.noaa.gov/seg/geomag/geomag.shtml