True Virtue Makes Dull Company!
Right on Sea Que!
The inherent errors in a magnetic compass are Variation and Deviation (no jokes folks, it's a technical term!).
Variation is the difference between true north (where Santa lives,and yes I have seen it) and this big blob of iron which lives up in the Queen Elizabeth islands. This blob moves a little bit every day to the west. For expmple, when Jesus walked the earth (or water or whatever) magnetic north was in Scandinavia!
Today our variation is about 16 degrees west in NH. In Florida magnetic and true north line up and there is no variation!
Deviation changes like crazy depending on your boat's heading. It is the change in your compass reading caused by metal in your boat, like engines and anchors, etc. When you are heading north the engine is directly behind you and may not influence the compass. When you are heading east or west it is perpendicular to the magnetic influence of the pole and pulls your compass either left or right. To compensate for this you should make up a "Deviation table" which can be used to mathematically correct the compass for each heading. OK for the Queen Mary but really not necessary here on the Lake.
Now pull out your Bizer or Duncan and take a look at the "Compass Rose". It is not the name of a boat owned by a Yachting wannabee but a depiction of a compass on your chart. It is full of information.
New question: What information is on the compass rose?
Misty Blue
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