NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Transcription of Worsley's Log
From: George Huxtable
Date: 2009 Mar 20, 23:13 -0000
From: George Huxtable
Date: 2009 Mar 20, 23:13 -0000
Thanks to Henry Halboth for confirming Worsley's calculations of the local time of his morning Sun observation at Elephant Island, before he set off on the boat journey to South Georgia. It confirms our own calculations too. There's complete agreement between us all, confirming Worsley's use of Norie's method 1, fot time-at-place, and the exactness of his calculations. A look at Brad's transcription, for 24 April, in - http://www.fer3.com/arc/imgx/f7-The-Log.pdf and comparison with Henry's numbers, will make that clear We're most grateful for Henry for adding to our confidence in that way. However, the relevant location was not, quite, at Cape Belsham, but at Camp Wild, a couple of miles to the East. That was the beach from which Worsley made his morning Sun altitude. Cape Belsham came in later, because it was a prominent headland which would remain identifiably in sight from some way off, after departure. It's splitting hairs, of course, to distinguish between two locations so closely spaced. but we are trying to tie down Worsley's chronometer errors as closely as we can. Worsley wasn't able to observe his latitude by a noon Sun sight, so had to take the best value he could for Camp Wild, presumably from a chart, and his log tells us that he presumed a value of S61� 04'. Unfortunately, because the morning observaion was made within 3 hours of local noon, the resulting chronometer error was rather sensitive to the correctness of that assumed latitude. It also depended on the correctness of the assumed longitude of Wild Camp, which Worsley took to be W 54� 19' 45", according to the log. Using modern charting (29104), Brad has found, with hindsight, that Worsley's position was at, or near, South 61 degrees 6 minutes and 15 seconds, Longitude West 54 degrees 52 minutes 12 seconds; see Navlist [7664]. With that assumption, he has recalculated the actual chronometer error to be 13 minutes 21.2 seconds, rather than the Worsley assumption of 11 minutes 55 seconds. That timing discrepancy of 86 seconds would stay with him for the duration of the boat journey. If anyone, such as Henry, is interested enough, and kind enough, to check over those numbers, Brad and I would be grateful. ===================== Things are falling into place nicely now. We're grateful for an off-list email from occasional Navlist poster Lars Bergman. He has helped us to interpret the otherwise-runic character string "N68E14 5.2.13.0=23' " as, successively, course, distance, dlat, departure, and dlong, the quantities that come straight from a traverse table calculation. George. contact George Huxtable, at george@hux.me.uk or at +44 1865 820222 (from UK, 01865 820222) or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---