On 21 November 1915 Sir Ernest Shackleton’s vessel Endurance was crushed by ice in the Weddell Sea and sank at a position given as 68°39¢30²S 52°26¢30²W. Close examination of the sextant sights recorded in Captain Frank Worsley’s original logbooks showed, however, that the location of the wreck would be offset from this position. The navigational methods and calculations that Worsley used to fix the position will be discussed as well as the reanalysis of the observations using modern techniques. Lunar occultation timings, performed in the southern winter of 1915 to rate the chronometers for longitude, were reduced using JPL ephemerides for the Moon and Hipparcos star positions and yield results that are significantly different from those obtained from tables in the Nautical Almanac of the time. Various factors are at play but when taken together they predicted that the wreck should lie to the south and likely to the east of the recorded position.
