NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Atherton's Heliostat
From: Gary LaPook
Date: 2010 Sep 13, 22:26 -0700
From: Gary LaPook
Date: 2010 Sep 13, 22:26 -0700
The article in Cruising World states that Atherton demonstrated his heliostat on board a full-rigged tea clipper off Tenerife. This was actually aboard the Royal Clipper last October on the transatlantic crossing from Lisbon to Barbados with a stop at Tenerife. I was there. I saw Atherton's device set up on a small tripod on deck, the device is about six inches across. I asked him what it did. He said that it was used to measure the altitude of the sun for navigation and that it used a pendulous mass to stabilize it and establish the level position. I couldn't see how it could be read to a precision of less than a full degree so it didn't appear to be very useful for navigation. He seemed like a nice old guy so I didn't tell him that pendulous levels don't work on shipboard due to accelerations, of course as a physicist he should have known that himself. I believe the way it works (although I did not study it very carefully since it looked like a non-starter to me so I might be wrong) is that the scale, like a protractor, is mounted on a base which contains a small mirror and this whole thing is leveled as a pendulum in gimbals. Since the angle of reflection equals the angle of incidence, the reflected sunlight will shine on the scale at the same angle that the sun light hit the mirror and is read against the protractor scale. This would work if you could ensure that the mirror was horizontal which you can't on a ship and the scale was only marked in degrees and there was no way to read it to a greater precision. So that's what I saw aboard the Royal Clipper. gl On 9/13/2010 5:56 AM, WF Jones wrote: > On page 31 in the September issue of "Cruising World" magazine is a > brief announcement entitled "Sun Sights: Easier Than the Sextant". It > is not clear to me how this device works. Some list members in the UK > may know of the inventor, Ted Atherton, a physicist who resides in > Wigan, England. My internet searches came back without a single > connect. Thanks in advance for sharing information and thoughts about > this device. > > > Regards, > Frank Jones > Rochester, NY > > > >