Hi Jim and others,
With regard to the GLOBE sundial. A type of sundial that could
also be call a globe sundial looks like a ball (a stone globe). The
gnomon is a thin plate that is hinged at the axis points of the ball (at
the north and south pole points of the globe) The axis of the globe is
made to be parallel with the axis of the earth. To read the time the
gnomon is turned until the shadow of the gnomon on the globe is the
smallest. The gnomon will now be over the correct hour line. The hour
lines are marked on the globe every 15 deg. The gnomon also had a
pointed section that is pointed towards the sun (to obtain the smallest
shadow on the globe).
This may not be the type of sundial that your friend wants to build but
I thought that your friend may be interested to know of this type of
globe sundial.
Roderick Wall.
On Feb 18, 9:33am, Jim Lattis wrote:
> Subject: "globe" dial
> Forgive me for issuing this query in place of doing
> my own research, but time presses....
>
> An artist friend wants to make a sundial of a particular design,
> which he describes as a "globe sundial designed by Thomas Jefferson".
> the rough sketch he sent me suggests that the dial face is
> carved on a spherical surface. he has no information about
> the gnomon. is this some kind of variation on a hemispherium?
>
> if anyone recognizes this design and can direct me to a source
> i may be able to make sure he doesn't waste time cutting
> stone before we have a clear idea of the concept.
>
> thanks very much. -jim lattis
>
> --
> Jim Lattis [EMAIL PROTECTED] "What's so
amazing that
> Director, UW Space Place voice: 608-263-0360 keeps us
stargazing, and
> U. of Wisconsin-Madison fax: 608-263-0361 what do we think we
might
> http://www.sal.wisc.edu/~lattis see?" -Kermit t.
Frog
>
>-- End of excerpt from Jim Lattis
--
_______________________________
Roderick Wall
E-mail: [EMAIL PROTECTED]
Melbourne Australia.
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