Brass Compass Shiny Wooden Base for ship useVessel owners and masters each have responsibilities for ensuring that magnetic compasses are maintained in good working order, adjusted and a table or curve of residual deviations is available.The performance of the compass should be monitored and, for a vessel more than 100GT, deviations recorded in a compass deviation book at regular intervals, ideally at least once every watch and also shortly after a large alteration of course.