Suunto SK-7 Compass

[Daryl Morse]

I got a Suunto SK-7 compass for Christmas (from my wish list). I've got a couple of questions about it.

Since I bought the compass in North America, it's calibrated for Region 1, which is North America. Does anyone know how well it will work in Region 5, which is Australia? I dive there when I go on business trips.

There is a small rubber "nib" in a hole at the end of the strap. What's it for? The strap won't go through the loop unless the "nib" is removed. Am I missing something?

 

[Uncle Pug]

the nib is there to keep the strap from going though the loop. remove it if you want the strap to go through the loop.

 

[Daryl Morse]

the nib is there to keep the strap from going though the loop. remove it if you want the strap to go through the loop.

I figured that part out. What I don't get is why wouldn't you want the strap to go through the loop? Am I missing something really obvious?

 

[Uncle Pug]

I'm not sure what Suunto's rationale was... but for a drysuit using dryglove rings I've left the strap loose but still on the arm during storage. The nub kept it from falling off and with the strap wide open I can put my arm in and afterwards cinch the strap up... even with drygloves on.

That said... I removed the nub for some reason... and now I can't find my compass.

 

[FloppyFoot]

I've got the same compass, but I didn't know it was 'calibrated'. Most compasses just point to magnetic north. You have to know the magnetic declination (degrees from magnetic north to true north) in order to make corrections. Realistically, with a hand bearing compass like the SK-7, it's not precise enough for the difference to true north to make much of a difference. Your compass should work fine almost anywhere.

PS Anyone notice that the tsumani in December moved the north pole by 1"?

 

[miketsp]

I got a Suunto SK-7 compass for Christmas (from my wish list). I've got a couple of questions about it.

Since I bought the compass in North America, it's calibrated for Region 1, which is North America. Does anyone know how well it will work in Region 5, which is Australia? I dive there when I go on business trips.

There is a small rubber "nib" in a hole at the end of the strap. What's it for? The strap won't go through the loop unless the "nib" is removed. Am I missing something?

The compasses for different regions simply have a counterweight in the right place to account for the fact that the compass needle will try to accompany the lines of force. So if you change hemisphere the needle will point into the ground and you have to incline the compass to allow it to turn freely. The reading will still be correct, it just makes it a pain to use.
I have a couple of northern hemisphere compasses and I currently dive in the southern hemisphere.

Compensation for local declination does not alter.

 

[miketsp]

Just another piece of information. Some manufacturers of compasses, unfortunately only for non-diving use so far, are now manufacturing multi-region compasses. These are manufactured using a circular magnet connected to a pivoting needle.

 

[miketsp]

I've got the same compass, but I didn't know it was 'calibrated'. Most compasses just point to magnetic north. You have to know the magnetic declination (degrees from magnetic north to true north) in order to make corrections. Realistically, with a hand bearing compass like the SK-7, it's not precise enough for the difference to true north to make much of a difference. Your compass should work fine almost anywhere.

PS Anyone notice that the tsumani in December moved the north pole by 1"?

Compasses are not "calibrated" by region but weight compensated for dip. See my post above.
I can't agree with you about declination being negligable. Where I am it's over 20degrees. That's certainly too much to neglect if you're planning a dive on a nautical chart.

As for the north pole moving, we're overdue for a complete inversion. Core samples from ocean bottoms clearly indicate that the north pole and the south pole switch places on average every 300000-400000 years and it's been around 700000 years since the last switch. How about waking up one morning and finding that your compass now points south?

Of course it's not that fast but I remember reading a New York Times article some time ago saying that there are indications that what could be the next inversion started slowly about 150 years ago and is now accelerating. The consequences would be drastic.

 

[Meng_Tze]

I believe that Suunto states that the SK-7 can accomodate up to 30 degrees tilt. This should be ample margin for a region 1 compass used in region 5?

I have a 'gobal' mapping/survey compass (bouth this global version because the needle house is quite thin and when surveying, I need a more accurate rose) and a SK-7. When simply finning around both are pretty much on par (barring declination)

Hope this helps

 

[miketsp]

I believe that Suunto states that the SK-7 can accomodate up to 30 degrees tilt. This should be ample margin for a region 1 compass used in region 5?

Region 1 to Region 5 is worst case, totally northern hemisphere to totally southern hemisphere. 30 degrees of tilt without locking may just about do but it will be a pain to read the compass. Remember that the counter-weight which worked to offset the dip in Region 1 will now contribute to the dip in Region 5.