Hi Brad,
My message re your interest in hemicyclia should have made it clear that it was
Fer De Vries’s original work on the construction of a Hemispherium that he
placed on his website and which was republished after his death by Frans Maes
and then placed on his own website for us to read today. My sincere apologies
to Frans!
Patrick
From: Patrick Powers
Sent: Sunday, October 22, 2017 12:40 PM
To: Brad Thayer ; sundial@uni-koeln.de
Subject: Re: Hemicyclium correction
Hi Brad
Further to your interest in an hemicyclium you might like to know of this link
to the former webpages of the late Frans Maes who set out his instructions for
“Construction of Hemispherium” some time ago and which is based on several
earlier documents – all referenced. You might find it useful – or at least
interesting!
http://www.fransmaes.nl/zonnewijzers/downloads/hemisph.htm
Good luck
Patrick
From: Brad Thayer
Sent: Monday, October 16, 2017 1:48 PM
To: sundial@uni-koeln.de
Subject: Hemicyclium correction
I am looking to make a hemicyclium-type sundial (half-hemisphere) in a metal
working class. What little I can find on them says they are inaccurate,
without being very clear on the problem. It appears to me the only issue is it
needs to be tilted so that the gnomon aligns with the Earth’s rotation axis;
thus the half-bowl faces south and the gnomon points south, but the end of the
gnomon that attaches to the bowl points north. Am I missing anything? I am
also looking to use an analemma-shaped gnomon to cast the shadow on the bowl,
and at least month lines for the solar elevation. The bowl will also have a
rod and bracket on the bottom to allow it to be rotated for daylight-savings
time and for local longitude corrections.
Thanks in advance -- Brad
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