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Hi Tracy,
You say " I may make lines that radiate from the center
out to the hour marks anyway." Please don't.
The hour marks are on the ellipse. The shadow falling on,
say, the 10 o'clock mark comes from a different direction depending on the time
of year. By standing on the correct date mark, you compensate for that. But
radiating lines have to radiate from somewhere, and that somewhere would be
wrong except on a couple of dates. Radiating lines would not help read the time
accurately, in fact they would mislead.
That's why I asked how big the dial was. For a given
latitude, the size of the dial is fixed once you've decided on the length of the
date scale (or vice versa). A ten foot long date scale inevitably needs a big
dial. I find a three foot date scale quite long enough in England.
A lot of people seem to think you must stand facing north
on an analemmatic sundial. In fact, it's better to stand with your back to the
sun, as your shadow will be more symmetrical and it is also easier to look up,
mentally extending your shadow out to the dial ellipse, or to hold both arms up
to make your shadow longer.
Best wishes
Chris
----- Original Message -----
Sent: Friday, October 27, 2006 6:52
AM
Subject: Re: date scale
Hi Roger
Thanks for the info. I have HUGE rocks for the summer,
spring/fall, and winter sunrises that lie just outside the sundial ellipse.
However, after reading through the seasonal markers section of your website I
now realize what the seasonal markers are. I placed the rocks so that the
"line" from the sundial to the horizon, where the sun rises, passes through
the center of the sundial! Oops! I am beginning to see now why this type of
sundial is in an elliptical shape - I never fully understood that. I also have
the seasonal sunrises marked further out on our property as well as the N-S
and E-W lines. But they all line up with the center of the sundial. I am
definitely going to add the "real" seasonal markers to the sundial. I have
been working on this sundial project for quite sometime. I started a long time
ago, and kept moving the location using portable hour marks. My shadow in the
summer just about reaches the hour marks. I may make lines that radiate from
the center out to the hour marks anyway. I really enjoy making this sundial.
It is fascinating to me. I love learning new things about these sundials -
some of it is over my head though and takes time to figure out. I
appreciate you all and the great information I have been getting. Thank you
again.
Tracy
p.s. I have not seen the Shaha Lake analemmatic
sundial....yet.
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