You've got to do a compass swing to determine the effects of the ships
magnetic interference.

Quite a few steps and you need a means to determine the magnetic heading of
the ship usign an external reference, preferable but is probably beyond the
means of most of us. Alternative is a GPS set to magnetic reading or if you
have local magnetic variations, then you can use the true North and apply
the variation.

In the following steps, try to be as close to the cardinal points as
possible.

1. Point ship North, take compass reading. Take reference reading. Note
error. If compass underreads, error is negative.
2. Point East, note reading. Take reference. Note error again.
3. Point South, note reading. Take reference. Note error.
4. Now, calculate North-South compensation. Sum both error and divide by
2.
5. Point North or South (easier to keep the South you are in)
6. Ajust the N-S screw to change reading by the results.
Example,
North your compass reads 003 deg, your external ref is 359deg ,
error is +4deg,
South compass reading 185deg, external ref is 180deg. error is 5deg
Step 4 calculation gives (4+5)/2=4.5 degrees.
Point South, first reading 185deg (assuming you managed to get the
same heading), adjust N-S screw until you get 180.5deg (185deg - 4.5deg)
7. Note new South reading and external reference reading. Calculate new
error.
8. Point West, repeat readings.
9. Calculate correction like in step 4.
10. Point West. Adjust E-W screw like in step 6 and example.
11. Note new West reading and external reference reading. Calculate new
error.
12. Point North, take compass and external ref reading.
13. Point East, take readings
14. Calculate index error, sum all 4 errors and divide by 4.
15. Physically rotate compass mounting to corrent for the error calculate
in step 14.
16. Now go through all the 4 cardinal headings, preferably 8 (the 45 deg
positions) and note compass readings and tabluate a Steer-by card.
17. You should get reading that are slightly out by 1 or 2 deg when you
tabulate the steer-by card and set you heading to those readings and you
will get the actuals.
Example: If the Steer-by card says 46deg for NE, it means you are
actually pointing 45deg when the compass is reading 46deg

Hope this helps.

Tan PS


"Jürgen Spelter" wrote in message
...
Hi,

I bought a dutch steal steel shipband I want to install a new compass.
Has anybody a tip how to adjust compass deviation?

regards

Juergen