NavList:

This post is directed toward Jeremy who is planning to remove 7 degrees of deviation from his ship's magnetic compass.

The following is the procedure as I remember doing it.

Prior to starting the quadrantal spheres and flinders bar are tapped with a hammer to knockout any permanent magnetism in the soft iron.

1. Head North by gyro (000). Raise or lower athwart ship magnets until the compass reads the correct magnetic heading.

2. Head East by gyro (090). Raise or lower fore and aft magnets until the compass reads the correct magnetic heading.

3. Head South East by gyro (135). Move the quadrantal spheres together symmetrically inboard or outboard until the compass reads the correct magnetic heading.

4. Head South by gyro (180). Raise or lower athwart ship magnets to remove half of the deviation.

5. Head West by gyro (270). Raise or lower fore and aft magnets to remove half of the deviation.

6. Head North West by gyro (315). Move the quadrantal spheres together symmetrically inboard or outboard to remove half of the deviation.

7. Swing the compass to record the remaining deviation.

Compass magnets remove permanent magnetism. Quadrantal spheres and flinders bar remove induced magnetism.

Greg Rudzinski
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