NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: How Many Chronometers?
From: Frank Reed
Date: 2009 May 10, 23:31 -0700
From: Frank Reed
Date: 2009 May 10, 23:31 -0700
Robert Eno, you wrote: "Determining your longitude and/or time via lunar distances for example, is only as accurate as the observer and his sextant and with so many variables (temperature, observer error, instrument error, refraction etc.) is it realistic for one to expect that he can determine chronometer error by this means? Unless your chronometer is out by hours." Even using lunars, historically it was not unusual to discover that the chronometer had gone bad. Here's a detailed historical example from 1849 which I wrote up for the list a few years ago: http://www.fer3.com/arc/m2.aspx?y=200507&i=024812 It's a great story, too. In the early 19th century, it was common practice to treat a difference between lunar longitude and chronometer longitude of less than 30' of longitude as "undecidable" --maybe the chronomer is off, maybe the lunar observation was off. But above that level of error, it was common to trust the lunar. As you know well, 30' of longitude would be an error of two minutes of time on the chronometer. -FER --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---