NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: No Lunars Era
From: George Huxtable
Date: 2004 Dec 6, 20:33 +0000
From: George Huxtable
Date: 2004 Dec 6, 20:33 +0000
Frank Reed wrote- >From the 18th and 19th century logbooks I've studied (only a sample of the >thousands out there), I've noticed a pattern. Lunars (lunar distance sights) >were never a primary method of navigation for American commercial vessels. >There was no "lunars era" comparable to the "chronometer era". Rather the >primary > method of determining longitude until the 1830s or so was dead reckoning, as >it had been for centuries. Around 1830, the primary method began to switch >over to chronometers. During the early period of lunars, from c.1770 to >c.1830, lunars were used as an occasional check on the dead reckoning. In >their >logbooks, navigators only occasionally updated their dead reckoning with >results >from their lunars observations. Rather, they continued their dead reckoning >until they were able to take a new departure from a point of land with >results of lunars listed marginally. The "mindset" was centered on the dead >reckoning. After c.1830 (and it is a decades long process of transition), the >primary longitude listed in the logbooks become "long by chrono" with >occasional >checks by lunars. and Henry Halboth added- "It would be of interest to consider whether all navigation calculations actually done aboard any particular vessel, aside from a notation of position, was actually spread out on the pages of the log book, as opposed to being calculated on scraps of paper or in a separate workbook which remained the possession of the individual." I think Henry has a worthwhile point here. Right from the earliest days of lunars, in the 1760s, printed pro-formas existed to systematise the calculations involved in a lunar. For example, Robert Bishop's form, dated 1768, can be seen copied into Howse's biography of Nevil Maskelyne (also in "The Quest for Longitude"). Later, around 1812, the English whaler William Scoresby the younger was using such forms, presumably pulled from a pad produced by Norie, which used a Mendoza method. Such observations would be taken at a particularly perilous point in his annual return journey South to Whitby, from the whale-fishery between Geenland and Spitzbergen, when it was essential to pass to one side or the other of the unlit skerries that surrounded Shetland. I think we need to recognise that otherwise well-found vessels were continuing to make ocean passages, well into the mid-1800s, without lunars or chronometers, still adhering to the old methods of latitude-sailing to find their way around the globe. George. ================================================================ contact George Huxtable by email at george@huxtable.u-net.com, by phone at 01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. ================================================================