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post #51 of 55 Old 07-21-2007
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sailaway21 said,
“The only time we can sail a "magnetic" course is when deviation is zero. Otherwise, we have no instrument that actually tells us our "magnetic" course,”

Does a fluxgate compass indicate magnetic north or is it also affected by deviation?
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post #52 of 55 Old 07-21-2007
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Now there you've got me Robert, because I am not familiar with the fluxgate compass and it's operation. What little knowledge I have of it would indicate that it would be effected by deviation but less than the standard compass as the fluxgate generates it's own magnetic field. I await others corrections, clarifications, or just plain "phooey" on the matter.


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Last edited by sailaway21; 07-21-2007 at 09:14 AM.
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post #53 of 55 Old 07-21-2007
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Sailaway...fluxgates are easily "deviated" by metal objects.
They can be compensated for deviation (and local variation in some cases) by the calibration process which involves sailing in a circle. But NEW metal objects put close the the fluxgate or any magnetic material and make them just as unreliable as a standard compass in similar circumstances.

A great article that is just a little dated on the various compass systems can be found at:
http://www.cruisingworld.com/article...=396&catID=568
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post #54 of 55 Old 07-22-2007
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Very interesting but it can be somewhat confusing. I find it easiest to simply remember that magnetic north is offset from the true north pole. The offset is the variation. This together with any compass deviation will alter the compass course from the true course. Then any adjustment becomes automatic as I can see why it occurs and what it must be.
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post #55 of 55 Old 07-22-2007
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Here is the deal. Since the magnetic north pole and the geographical one are not co located we face a situation called magnetic variation. There are lines drawn on a chart that have either easterly or westerly variation. Now the reading on your compass as you see it is your magnetic heading but you need in most cases to apply the variation. West you add and east you subtract to get your magnetic course. For example you want to steer a 090 course and your line takes you through a area of 21West variation you would steer a magnetic heading of 111 degrees. Remember east is least and west is best. Hope that helps.



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