A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Ed Popko
Date: 2018 Dec 21, 06:48 -0800
"Navigation of the Shackleton Expedition on the Weddell Sea pack ice" is really a nice paper. It's a rare and clear example of how lunar ocultations were used to find GMT. It's great to see how-it-was-actually-done. The glossary is a big help to anyone learning lunars techniques. It's also fortunate that there is a relevant surviving photo. Some were rescued from the sinking ship and I guess it was just luck that this one was in the batch. The very high quality images of notebook pages and their transcriptions are very nice. I'm surprised how well the notebook calculations are anotated and that the handwriting is good with minimum 'erasures' (over writing). You are also reminded how important rating chronometers were. Easy to forget this when today's $15 doller quarts wristwatch loses only a second or two each month.
This paper brings to mind Captain George De Long's ill-fated Jeannette Expedition of 1879. De Long became ice-locked while searching for the mythical 'Open Polar Sea' believed to be near the Chukchi Sea above Alaska. He was not taking lunars as they had many chronometers aboard but he did used celestial shots to track how the ice pack and their crushed ship drifted. The news was all bad - they were drifting further north and away from sources of help. It did motivate them, however, to abandon-ice and use their lifeboats to sail south west to the coast of Russia.
Nice job Lars and Robin!