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Brooke,

If you knew where you were, the elevation of the sun would suffice for
determining the time, and 1 second accuracy could be achieved with a
marine sextant and suitable horizon.  Accuracy would be higher when the
azimuth of the sun was closer to east or west than north or south.

Fred Hebard

On Sunday, Aug 10, 2003, at 01:52 US/Eastern, Brooke Clarke wrote:

> Hi Richard:
>
> I think you can get 15 seconds accuracy at any time the Sun is
> shining.  There are a number of heliochronometers that do it.  But
> it's not a static sundial, that's to say you need to turn dials, etc.
> In the extreame case you could use a surveyous transit/theodolite to
> shoot the az and el of the Sun and using data for the current year
> know exactly the time to about a second.  See:
> http://www.cadastral.com/
>
> I did not file down the tacks.  The heads are a little less than 1/8"
> diameter and were seated so only a tiny fraction of an inch was
> sticking up.  You can feel the head with you fingers.  No problem to
> walk on them bare foot.
>
> Have Fun,
>
> Brooke Clarke, N6GCE
>
> Richard M. Pisko wrote:
>
> On Sat, 9 Aug 2003 13:37:34 -0700, Brooke Clarke wrote:
>
>
>
> I made one of these by placing a metal plate at the lower end of a
> South
> facing skylight and using a 3x5 card with a number of concentric
> ellipses and a small hole at their center.  I just tracked the Sun's
> image with the card and at exactly noon stopped and drive a small brad
> nail into the hardwood floor.  After many years there would be more
> than
> one nail for the same date because as we go through the 4 years of the
> leap year cycle the timing is a little different.
>
>
>
> Thank you.  Got it now ... not all the details, but the general idea
> ... and will visit your referenced sites.  I read too much into your
> comment, and was thinking of 15 second accuracy at any daylight hour.
> A bit difficult, I thought.   :-)
>
> Did you sand the (copper or steel?) brads flush?
>
>
> --
> Richard ...
>
>
>
>
>

   

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