Hi Ken,
One of the most beautiful (IMHO) is the Schmoyer dial which
incorporates the EOT in the gnomon. You can see a picture of the dial at:
http://www.precisionsundials.com/schmoyer.htm
best wishes,
Peter
On 4/02/2013 6:32 AM, Ken Baldwin wrote:
Hello,
I'm a new list member, and have a beginner question:
Are there examples of sundials whose sole (or primary) purpose is to
compute the Equation of Time for the current date?
- I know that this information is often provided as a graph in the
furniture, but why should I have to know the date and perform the
look-up manually? Can't I use the position of the sun to do the
computation for me?
- I know that the EOT correction can be incorporated into the layout of
(some) hour lines, but I'm more interested in having dials which show
true solar time. I'd like a separate device dedicated to computing the EOT.
- I know that I can construct an analemmic noon mark to show the EOT for
that day, since it's simply the east-west component of the analemma, but
I'd like a design that can be read at any daylight hour.
It seems to me that it should be possible to build such a dial, since
the EOT is a function of date, and date lines can be read from many
sundials. In principle, I can just re-label the date lines with
corresponding EOT values and interpolate.
I hope that makes sense. But since I haven't seen anything like that in
introductory sundial books, I must be missing something... Is it that
the shadow length can't be read accurately enough to get a reasonably
precise EOT estimate? Or is it just too hard to make a readable layout,
given that solar altitude is ambiguous between two dates, and that the
component of the EOT due to the eccentricity of the earth's orbit is out
of phase with the equinoxes and solstices?
Thanks in advance,
Ken Baldwin
Corvallis, OR USA
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