I’ve been watching Chasing Shackleton, a 3-part documentary about a group of men who recreated the epic 16-day, 800-mile journey of Sir Ernest Shackleton and five other men in a small boat through one of the roughest stretches of ocean from Elephant Island to South Georgia Island to summon a rescue mission for the rest of their crew they had left behind. The men in the documentary used a similar small boat and clothing/technology of the time, including a sextant and clock for navigation. It’s a testament to skill (and probably a good bit of luck) that anyone - either Shackleton’s group, or the modern recreators - was able to hit South Georgia Island instead of being blown right past it into thousands of miles of empty ocean.
So how much luck was involved? More specifically: how precisely can one navigate using a sextant and a clock while perched on a small boat that’s being tossed on big waves? The Wikipedia page for the sextant describes the accuracy limits of the sextant itself, but what about the mechanical clock that they were using for timekeeping (I’m aware that accurate clocks have historically been a challenge for determining longitude)? And what about the unsteadiness of such a small boat? How much might that have affected sextant readings?