Suunto SK-7 Compass

[Daryl Morse]

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.

OK, I think I finally understand. Remove the nub, thread the strap through the loop, replace the nub. Now the compass won't fall off even if it comes undone. DOH!

 

[Daryl Morse]

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.

Is Region 1 to Region 5 worst case? Take a look at the map: http://www.suuntousa.com/declination.htm. It appears that the declination for Vancouver is 20E and for the Sydney area, it's around 10-15E. Maybe that won't cause a problem.

Or is the issue of declination completely separate from counter-weighting? Suunto talks about that as well: http://www.suuntousa.com/needle.htm. I think I'll send an email to Suunto for clarification. I don't think the SK-7 compass has a "global needle".

 

[miketsp]

Is Region 1 to Region 5 worst case? Take a look at the map: http://www.suuntousa.com/declination.htm. It appears that the declination for Vancouver is 20E and for the Sydney area, it's around 10-15E. Maybe that won't cause a problem.

Or is the issue of declination completely separate from counter-weighting? Suunto talks about that as well: http://www.suuntousa.com/needle.htm. I think I'll send an email to Suunto for clarification. I don't think the SK-7 compass has a "global needle".

Declination has nothing to do with dip.

Declination is caused because the location of the magnetic pole does not correspond exactly to the real geographical north pole, so depending on where you are on the globe there is a sideways error.

Dip is because the lines of magnetic force are parallel to the earth's surface near the equator and go down into the globe at a steeper angle as you get nearer the magnetic poles. Imagine you were standing exactly on top of the magnetic north pole. If you had a light compass needle it would try to point down into the ground.
So the counter-weight is to bring the needle back horizontal.

 

[Daryl Morse]

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.

I brought the compass to Australia just to see how it would behave. It doesn't work properly. Here in Fremantle where I'm currently staying, the indicator is inclined by about 30 degrees. For all practical purposes, it's unusable.