How to compensate a compass:
You will need a second compass to be used as the reference for your
steering compass; a hand bearing compass is often the most convenient,
provided it is interference-free. The north-south labelled screw on the
compass corrects the north-south heading; the east/west screw corrects
the east-west heading (see figure E).
- Run your boat under power along a northerly course as indicated by
your hand bearing compass and adjust your steering compass by turning
the north-south screw either way, until the steering compass also points
north.
- Repeat the procedure, running the boat on an eastern course, adjusting
your steering compass by turning the east-west adjusting screw until the
steering compass points east.
- Run the boat on a southern course reducing the deviation by half.
- Run the boat on a western course reducing the deviation by half.
Note: Upon completing the compensation procedure, it is important to plot
a new deviation curve.
4.
Lighting
Our compasses with lighting include in series a 12V bulb and two wires
twisted around each other to avoid interfering with the magnetic field.
Compasses equipped with 2 x 12V bulbs can be used on 24 V power,
when the provided bulbs are mounted in series (see figure D).
5.
Utilisation
You can now use your compass. It must be read from the front (see figure
A : Front Reading / B : Double Readig / C : Back Reading), with the lubber
line (1) indicating your boat’s heading. Some compasses have lubber lines
(2) on either side to enable accurate readings whatever the angle.
Keep in mind that even the proximity of a simple screwdriver may cause
important deviation and give you a bad course reading.
To calculate your course, use the following formula TH = MH + V + D
TH : true heading (determined on the marine chart)
MH : magnetic heading (indicated by the lubber line (1))
D : deviation (see paragraph 2)
V : variation (shown on marine chart).
