NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Calibrating a sextant scale
From: Frank Reed
Date: 2007 Dec 02, 23:30 -0500
From: Frank Reed
Date: 2007 Dec 02, 23:30 -0500
Dan Allen, you wrote (regarding calibrating by measuring angles between lighthouses that add up to some known angle, 360 degrees for starters): "where did you do this? Perhaps a few such locations could be given on the list so we could go try this out..." I do this near Eastern Point in Groton, Connecticut at the mouth of the Thames River. I have to trespass a little to get the spot I like, but there's also some opportunities for checking some angles at Stonington Point --where you and a group of us shot lunar distances back in September, 2004. By the way, for those familiar with the English river of the same name, the Thames in Connecticut is pronounced to rhyme with Names. I've often wondered whether the English River was pronounced that way neary 400 years ago when the Connecticut estuary was named. This Thames separates Groton and New London, Connecticut. New London was once a thriving whaling port, then a small general port, but it died in the late 20th century. The Groton side of the Thames is home to the US Sub Base (barely saved from closure a couple of years ago), the USS Nautilus museum (first nuclear-powered sub), as well as the "Electric Boat" division of General Dynamics which still builds new nuclear submarines. All of this is about five miles west of Mystic, Noank, and Mystic Seaport. You also wrote: "PS - I see a new appendix in a future edition of Bowditch: a list of locations where sextant errors can be measured!" Well, maybe in some other book for sextant enthusiasts. I've been thinking of other possibilities. Bays and sounds are the best bet. I wonder if there's a good spot in San Francisco Bay. I've also wondered about the possibility of observing from the top of a small hill in relatively flat country, but if the objects are out of the horizon by half a degree or more, the error is too large. I did come up with another possibility: how about a nice dry lake bed? There are plenty that are flat as a pancake for miles. Set up posts around the radius of a circle at roughly equal angles, and voila, a sextant calibration observatory! Do you know if one would need special permission to go out onto the flats west of Great Salt Lake and drive posts into the ground? Or any of the So Cal lakebeds? -FER --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---