RE: civil time and polar dials

[Albert Franco]

 

It seems that as Roger said it would make the base slanted at a cockeyed angle.  And intuitively I'm not sure the hour lines would stay in the proper alignment with the shadow planes.  The west side would start to rise and it seems that the shadow planes of each hour would cut through the face/base plate at a different angle for where ever you stop rotation.

 

I'm thinking of figures two and three on this website:

 

http://home.iae.nl/users/ferdv/shadow1.htm

 

My thought is the only dials which can be adjusted in this way are dials whose gnomon points directly at the celestial north pole AND whose base/face plate is perpendicular to all shadow planes.  Only then will rotation allow the hour lines on the face to keep the proper angles and alignment throughout rotation.  The only dials I can think of that fit this description are equatorial dials, but I am newer to this than most people on this list.

 

Any corrections or feedback?

 

Albert Franco

35N  95W

 

 

Roger Bailey <[EMAIL PROTECTED]> wrote:

Hello Ed,

One caution on this rotation technique. As Edley states you rotate the
entire dial around the polar axis. After rotation the horizontal dial plate
will no longer be horizontal. This is the problem with these tilt or
rotation corrections. The resulting dial may show civil time but it looks
odd.

Roger Bailey
Walking Shadow Designs
N 48.6 W 123.4



-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Behalf Of Edley McKnight
Sent: January 14, 2004 10:27 AM
To: sundial@rrz.uni-koeln.de
Subject: Re: civil time and polar dials


Hi Ed,

As far as I know, any dial with a gnomon parallel to the earth's axis
may be corrected for EOT, Longitude and Daylight Savings Time by
rotating the entire dial around that axis. Since they are all based onthe projection of an equatorial dial.

Hope this helps!

Edley


> Hello All.
>
> As a beginner to the fascinating study of gnomonics, let me say first
of all
> that it was especially rewarding to discover that a list such as this
exists,
> whereby novices such as myself may consult with professionals and folks of
all
> levels on matters of our mutual interests in dialing. So thanks in advance
to
> any who might be able to answer my question.
>
> On a properly designed and aligned polar dial, is it possible to adjust
for
> EOT and longitude correction by rotating the dialplate along the axis of
its
> gnomon, or is this type of correction only effective on equiangular dials,
such
> as the equatorial? Will this technique work on horizontal dials as well?
>
> Again, my thanks in advance for guidance with my simplistic question.
>
> Ed Olander
>
>
>
>
> ------------------------------------------------------------
> http://Game.37.com/ <--- Free Games
> http://newJoke.com/ <--- J O K E S ! ! !
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