Deviation is specific to the vessel. The effects that certain metals, or electronics
have on your compass. Deviation can change with the heading of the vessel. You can create a Deviation table for your vessel by steering
through a variety of courses, or swinging the vessel.. There are good methods for doing this already in print. Try Chapmans.
COMPASS ERRORS | VARIATION | DEVIATION
Variation changes with Location, and the time..Annual changes. Your chart should give you the variation for the area in question.
Some people refer to Deviation when talking about the dipping of the compass at higher, lower latitudes......I believe you are talking about a deviation table for the ships compass.