when i was racing offshore sailboats from new england to bermuda in the 1970s-80s we used such a sextant to navigate. i haven't followed the offshore racing circuit for years but i am quite sure boats using GPS still receive a significant negative handicap. these are amazing tools and are still in use today. any captain or navigator sailing the oceans should be proficient in their use because, aside from keeping old traditions alive, in the event of failures in the electrical system on board the only way to know where you are and what compass course to take is to by using a sextant together with a precise clock, knowledge of the stars, sun and moon and charts and tables. it is not hard to learn but it takes practice to become proficient. my father passed his sextant to me and i recently passed it proudly on to my son.