Compass has a half-life of only about 12 years, so a compass that contains 120 mCi of tritium when new will contain only 60 when it is 12 years old, 30 when it is 24 years old, and so on. Consequently, the illumination of the display will fade. Mariners' compasses can have two or more magnets permanently attached to a compass card, which moves freely on a pivot. A "lubber line", which can be a marking on the compass bowl or a small fixed needle, indicates the ship's heading on the compass card. Traditionally the card is divided into thirty-two points
Azimuth compass an azimuth compass designed by Gowin Knight to Joseph Banks for the voyage of HMS "Resolution" commanded by Captain James Cook in 1772. The instrument cost ₤80.0.0. On 6 February 1808 the American sealer "Topaz", commanded by Captain Mayhew Folger, arrived at Pitcairn Island to take on fresh water. There he found thirty five survivors of the Mutiny on the Bounty led by John Adams, who gave Folger the HMS "Bounty"'s azimuth compass and chronometer. Azimuth compass An azimuth compass (or azimuthal compass) is a nautical instrument used to measure the magnetic azimuth, the angle of the arc on the