11 Apr 2008 14:05:12

Hi-Soft

Compass calibration ?

How important is it to have a compass calibrated to the Southern Hemisphere ( for mainly diving locally in Asut )...as opossed to one calibrated to the Northern hemisphere ? I've heard you just need to angle the later slightly when using it, as the "pole" is pulled downward causing it to stick sometimes... Like is it not that much of a drama ? cheers, BC

11 Apr 2008 08:51:37

marcin dobrucki

Re: Compass calibration ?

Hi-Soft wrote: > How important is it to have a compass calibrated to the Southern Hemisphere > ( for mainly diving locally in Asut )...as opossed to one calibrated to the > Northern hemisphere ? > > I've heard you just need to angle the later slightly when using it, as the > "pole" is pulled downward causing it to stick sometimes... > > Like is it not that much of a drama ? Depends. The magnetic declination varies widely around the world, if you do long swims, it might well put you a good deal off-course. I would guess you are not diving anywhere close enough to the magnetic poles for compas inclication to be a problem. But perhaps I still missed something? /m

11 Apr 2008 12:38:05

Al Wells

Re: Compass calibration ?

In article <47fee379$0$1233$5a62ac22@per-qv1-newsreader- 01.iinet.net.au >, bjcanham-nospam-@hotmail.com says... > How important is it to have a compass calibrated to the Southern Hemisphere > ( for mainly diving locally in Asut )...as opossed to one calibrated to the > Northern hemisphere ? > > I've heard you just need to angle the later slightly when using it, as the > "pole" is pulled downward causing it to stick sometimes... > > Like is it not that much of a drama ? Compasses are made for 5 different magnetic zones. There is a downward force from the magnetic poles, and a compass that is used between a pole and the equator will have some dip on one end. The other end of the needle is counterweighted to compensate for this. A compass made for zone 1 (the US) will tilt about 8 degrees down on the southern end in Australia (zone 5). The southern end may drag on the bottom or the northern end may drag on the top. It's best to get a compass for the zone you're in. I would buy the right compass instead of trying to save a few dollars by ordering one from the US or Europe, unless you can order a zone 5. I've used a Zone 1 compass in Zone 2 with no problem, but I have no experience with my compass in zone 5. In diving, we're not usually trying to correct to true north; we just want some sort of repeatable reference. There are global compasses available, but I haven't seen them in diving.

11 Apr 2008 14:32:55

Hi-Soft

Re: Compass calibration ?

"Al Wells" <al.wells@gmail.com > wrote in message news:MPG.2269258e37341bbc989a2a@news.verizon.net... > In article <47fee379$0$1233$5a62ac22@per-qv1-newsreader- > 01.iinet.net.au>, bjcanham-nospam-@hotmail.com says... >> How important is it to have a compass calibrated to the Southern >> Hemisphere >> ( for mainly diving locally in Asut )...as opossed to one calibrated to >> the >> Northern hemisphere ? >> >> I've heard you just need to angle the later slightly when using it, as >> the >> "pole" is pulled downward causing it to stick sometimes... >> >> Like is it not that much of a drama ? > > Compasses are made for 5 different magnetic zones. There is a downward > force from the magnetic poles, and a compass that is used between a pole > and the equator will have some dip on one end. The other end of the > needle is counterweighted to compensate for this. A compass made for > zone 1 (the US) will tilt about 8 degrees down on the southern end in > Australia (zone 5). The southern end may drag on the bottom or the > northern end may drag on the top. > > It's best to get a compass for the zone you're in. I would buy the right > compass instead of trying to save a few dollars by ordering one from the > US or Europe, unless you can order a zone 5. I've used a Zone 1 compass > in Zone 2 with no problem, but I have no experience with my compass in > zone 5. > > In diving, we're not usually trying to correct to true north; we just > want some sort of repeatable reference. > > There are global compasses available, but I haven't seen them in diving. Yeah, I figured as much re the distances, and constant reference point...so it probably won't be that big a deal either way... just that some places mention they have northern or southern claibrated option, and some just have the Northern...will try to get the correct type if possible..