Beginning with the basics of magnetism, the author discusses how to ap compass error (variation, deviation, misalignment, lazy and frozen compass, intermittent deviation) to find the true course and how to measure error by taking bearings, inland and offshore. For celestial bearings, the book includes two tools: a Compasss Corrector for bearings on the sun; and a Skyclock for bearings on Polaris. There are step-by-step instructions on how to swing ship, set up deviation tables and adjust compasses, regardless of size or type of vessel.