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    Re: Atherton's Heliostat
    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
    >
    >
    >
    >
    
    
    
    
    

       
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