Can a European compass be used in Australia?

M

Mark The Convict

Guest
#1
Generally speaking, can a compass that's calibrated for use in the Northern Hemisphere be used with reasonable accuracy in Australia? A net search has yielded much varied and unhelpful opinion. Although fairly competent in nav (except for that one time), I know nothing about this, because we didn't need to know it, so it wasn't taught.

I ask because I'm thinking of buying a Silva 54B, and object mightily to being gouged $250-$300 for a compass that's about 60 quid on Ebay UK. Obviously, I can't go to the Q Store and be told to '**** off, it's a starred item!', so I might as well be told to **** off here instead.:blowkiss:

Am not keen on GPS, largely because of Murphy's Law, battery replacement, signal strength, potential for damage etc. etc.

TIA,

Mark.
 

Travelgall

MIA
Kit Reviewer
#2
Wah.
No the needle is thrown off by being repelled by any cans of piss weak Australian Lager in the vicinity.
 
#3
Aren't hand compasses counterweighted for whichever hemisphere you happen to be in?

Which means they won't work in the wrong one.


Just found this
To determine direction, the compass uses a simple bar magnet with two poles. The bar magnet in the compass is mounted so that it can rotate freely and align itself automatically with the Earth's magnetic field.

However, magnetic compasses are subject to a problem called "magnetic dip" because the lines of flux of the Earth's magnetic field are not parallel to the Earth's surface (except at the magnetic equator). Since the compass needle aligns itself with the lines of flux, the north-seeking end of the needle tends to dip toward the Earth (in the Northern Hemisphere). This dip angle is caused by the vertical component of the Earth's magnetic field and increases from zero at the magnetic equator to almost 90 degrees near the magnetic pole. Many magnetic compasses (including those used in aviation) have a small weight on the south-pointing (again in the Northern Hemisphere) end of the needle to counteract this magnetic dip by using gravitational force. That is, a counterweight is added to the end of the compass needle which points away from the magnetic pole. This arrangement does, indeed, almost completely fix the dip problem and has been used on compasses for many years.
So the answer is no your compass won't work properly.
 

wedge_cadman

War Hero
Kit Reviewer
Book Reviewer
#4
There are northern-hemisphere and southern-hemisphere compasses. The magnetic field lines to which a compass needle aligns point into the earth at the north and south magnetic poles. So in the northern hemisphere, the north end of the needle is pulled downwards and so the south end is counter-weighted to balance the needle.
If you were to use a northern hemisphere compass in the southern hemisphere then the south end of the magnet is pulled downwards by the magnetic field and is also heavier, due to the counterweight, than the north end - resulting in a needle that catches and drags on the bottom of the compass housing when the compass is held horizontal.

Mostly nicked off the tinterweb
 
#5
Compass Technical Information - Document #313 - EZ Facts Safety Info - Lab Safety Supply

Compass Zones

In order to get accurate readings from a compass, the needle must be balanced in the vial so that it does not drag. Due to the components of the Earths magnetic field, a compass that works in the United States will drag or stick in Brazil. To remedy this problem, the compass industry has developed five compass zones (see zone map below). Here is a list of the major countries in each zone.
 
M

Mark The Convict

Guest
#6
Thanks everyone. Travelgall, the beer-like fluid is used for needle damping, being unfit for human consumption (except for a few excellent beers that I'm not going to tell you about)
 

Travelgall

MIA
Kit Reviewer
#7
I'm sorry but there's no difference in compasses for the Northern and Southern Hemispheres except a small weight on the needle that you're paying an extra $45AUD for the privelege. Otherwise ships would all have different compasses with the words North and South underneath them and captain Cook would have got lost shortly after passing Equatorial Guinea. What is different is the Magnetic Variation which is on your map which is used to adjust your compass. It could be argued that due to magnetic flux lines you could get a sticking needle due to the vertical dip, the solution to this is to hold the compass at an angle so it doesn't stick or buy a compass with an allowance for a fairly large vertical play in the needle.
 
M

Mark The Convict

Guest
#8
And what would happen when ships crossed the Equator? There'd be carnage! Plus there's that water-swirling-down-the-plughole thing (Cooper's and Malt Shovel Brewery are quite good)
 
#10
I'm sorry but there's no difference in compasses for the Northern and Southern Hemispheres except a small weight on the needle that you're paying an extra $45AUD for the privelege. Otherwise ships would all have different compasses with the words North and South underneath them and captain Cook would have got lost shortly after passing Equatorial Guinea. What is different is the Magnetic Variation which is on your map which is used to adjust your compass. It could be argued that due to magnetic flux lines you could get a sticking needle due to the vertical dip, the solution to this is to hold the compass at an angle so it doesn't stick or buy a compass with an allowance for a fairly large vertical play in the needle.
A ships compass is a somewhat different construction than a handheld silva.

And what makes you think that Captain Cook et al had any idea where they were?
Columbus and India springs to mind here :)
 

Ravers

LE
Kit Reviewer
Book Reviewer
#16
When you cross the equator for the first time, Neptune comes and fucks you up with some bears. They force feed you chilli sauce and beer until you spew, then you get dunked in a pool of slimey shit.

That's more or less what happened to me anyway, I can't remember all the details, I was pretty smashed at the time. I don't recall if it had any effect on my compass.
 
M

Mark The Convict

Guest
#17
'Geomagnetic reversal', eh? In that case, I can navigate by the glow of burning cities (an established concept here, before anyone alleges otherwise)
 
#18
If you live down there buy a local compass...

If you are just visiting your normal compass will work, you just have to be careful with it. Certainly the 'deep' compasses such as issue prismatics don't suffer the drag problem to the same degree as teh shallow 'silva's.
 
#19
Strange 'cos when I was in the Antipodes and went to the Q stores for a compass, I was given a standard Brit Army marching compass complete with UK NSN. It worked so well that I forgot to hand it in and it is still working well in the northern hemisphere.
 
#20
You should have tried harder at school.If you'd commissioned as an officer you'd be able to let your chaps worry about such trivial matters while you concentrate on being fabulous and dashing.
 

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