im wanting to buy a glabally balanced compass, ive recently got a silva voyager, but think ive been unlucky with air bubbles (in 2 of), can anyone recommend a good base plate one- - it has to work in tropical asia at least. ta!
I've got a Recta DT420G which has a little screw in the base plate to change magnetic declination. The screwdriver, so to speak, is a small metal piece supplied with it, which you can attach to the lanyard. It seems a good quality, solid, quiick reacting compass. Not used it abroad, so I can't coment on the accuracy, but I have fiddled with the decination settings and they seem to work simply.
I'm not sure I would really want to trust micro navigation to my decination setting though, so I might be tempted to use add/subtract mentally to get around the problem.
Paul, you haven't been unlucky with the Voyagers - they break easily. As one squeezes the capsule to preset the declination (why?), it's too easy to burst the capsule and allow oil out/air in.
I know this as I've just done it. Bought the wretched thing especially (as my favourite Suunto M-9 sticks like a sticky thing in Suid Effrika) and just been fiddling about with it. Squeeze - hiss - oh look at the bubble - oh poo, smell the turps. Flying out Saturday, so there's no time to replace it.
Whatever possessed me to try to preset the declination? It's not that difficult to add or subtract 23 after all!
Interesting. If I've understood correctly, the OP was concerned about compasses working in both the Northern and Southern hemispheres, where the magnetic inclinations are different - wikipedia says:
Because the Earth's magnetic field's inclination and intensity vary at different latitudes, compasses are often balanced during manufacture. Most manufacturers balance their compass needles for one of five zones, ranging from zone 1, covering most of the <a href="http://en.wikipedia.org/wiki/Northern_Hemisphere" title="Northern Hemisphere">Northern Hemisphere</a>, to zone 5 covering <a href="http://en.wikipedia.org/wiki/Australia" title="Australia">Australia</a> and the southern oceans. This balancing prevents excessive dipping of one end of the needle which can cause the compass card to stick and give false readings.
When I sailed in NZ, my UK handheld compass wasn't happy and kept trying to touch the baseplate, so I bought a local one, which doesnt like the UK, so these at least were intended for different inclinations.
Yeah, that's the theory but like I said above I didn't find any problems using my bottom of the range Silva 7 in practice. Just tilt it slightly maybe. Ofcourse you mostly just follow the little orange triangles tramping in NZ so I only had to get it out a couple of times off track.
To a lesser extent, Judy, yes. Most walking compasses are needle compasses, however, not card compasses, so the effect is less noticeable. Indeed, as Steve says, a bottom of the range baseplate needle compass will work OK (with tilting). Having a bubble to chase doesn't help though (
Alternatively, if one prefers a sighting compass, a military Pyser-SGI prismatic or Commenga lensatic should work as the bowls are (allegedly) deep enough to accommodate the dip/inclination. Using a slim card compass, eg, a Suunto M-9 or Silva Type 54, however, usually results in the card clipping the capsule and sticking as with marine hand-helds and hand bearing compasses. With any sighting compass, tipping isn't really an option as this will often tilt the aiming mark too.
My point, as also found by the OP, is that the Silva Voyager global series uses an adjustable declination facility that requires one to hold the capsule firmly between finger and thumb whilst turning the bezel. Squeeze too hard and one pops the seam around the base of the capsule, braking the integrity of the seal and introducing a bubble.
As a general rule, therefore, folks, resist the urge to squeeze a Silva compass capsule )
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