Even with all our electronics, sextants – dating to 1759 – are making a comeback. The Navy, for example, has reinstituted its celestial navigation and sextant training because of fears about jammed GPS satellite signals. Whether you’re on a warship or a 65-foot blue-water cruiser, if you lose your electronics, for whatever reason, in the middle of the ocean, it certainly would help to have at least a working knowledge of celestial and a sextant. As Davis Instruments points out, with a wristwatch, a copy of The Nautical Almanac and a chart, you could find your way back home using…