Re: Hemicyclium correction

2017-10-23 Thread Michael Ossipoff
In the Hemicyclium discussion, the OP mentioned having 6-inch copper
tubing. So, though it was a bit off-topic, I suggested that the tubing
could be used for an additional, quicker, project, to make a south
windowsill sundial--a Circumference-Aprerture Cylindrical Equatorial Dial.

But, when I said that the axial dimension of the cylinder has to be at
least 0.4335 times the diameter, I neglected the fact that there are south
declinations as well as north declinations. (...funny, because we're in
south declination now) So, with the circumference aperture in the middle of
the cylinder, the cylinder's axial dimension has to be at least twice
0.4335, which is about 0.867 times the diameter.

But my suggestion for marking points of the declination-lines for each hour
was correct:

At any hour-line, the axial displacement of a declination-line from the
equinox-line is equal to the tangent of the declination times the direct
distance between the circumference aperture and the intersection of that
hour-line with the equinox-line

That amounts to:

(Tan dec)(R*2Sin(h) ).

...where h is the number hours from 12 noon.where R is the cylinderr's
radius.

Obviously more neatly written:

(Tan dec)(DSin(h) ).

...where D is the diameter of the cylinder.
-

But a cone would be better than a cylinder, because it opens toward the
north, the direction from which it would be observed--making it readable
from a wider-range of directions, and making the inside surface more
readable in generral. The use of a cone just slightly more complicates the
declination-lines, but that would take this post even more off-topic.
--

I mentioned that I'd read of a drinking-cup with a hole in it being used as
a cylindrical sundial. Of course if it were a Cylindrical Equatorial,
orienting it just by estimation wouldn't give very accurate results. (A
Cylindrical Equatorial is supposed to be a *mounted* dial, not a portable
dial).

But actually, maybe they were talking about a Cylindrical *Altitude* Dial.
But, though that avoids the direction-estimation, the drinking-cup would
need a way of hanging it in the right orientation, and so it wouldn't be
much like an ordinary drinking-cup. ...and the line-marking would be
complicated by the non-cylindrical shape of the cup.

Michael Ossipoff

On Mon, Oct 16, 2017 at 8:48 AM, Brad Thayer 
wrote:

> 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
>
> ---
> https://lists.uni-koeln.de/mailman/listinfo/sundial
>
>
>
---
https://lists.uni-koeln.de/mailman/listinfo/sundial



Re: Hemicyclium correction

2017-10-23 Thread Dan-George Uza
I find the video below extremely instructive!

https://youtu.be/0hs6QqwJIhs

The sundial is marked in old temporary (or seasonal) hours. Changing them
to modern hours does not make much sense to me.

For it to become a hemicyclium I guess you just have to leave out the
unused part of the half-sphere.

Dan Uza


On Sun, Oct 22, 2017 at 2:40 PM, Patrick Powers <
patrick_pow...@compuserve.com> wrote:

> 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
>
> --
> ---
> https://lists.uni-koeln.de/mailman/listinfo/sundial
>
>
> ---
> https://lists.uni-koeln.de/mailman/listinfo/sundial
>
>
>
---
https://lists.uni-koeln.de/mailman/listinfo/sundial



Re: Hemicyclium correction

2017-10-23 Thread Maes, F.W.
Hi Patrick,

Thanks for pointing this out. Fortunately, I am still alive and sometimes
kicking a bit ...

I put the link to Fer de Vries' article temporarily on my own website as it
was the quickest and easiest way to answer a query by someone on this list.
By now, the (same) article is also available on the website of the Dutch
Sundial Society.

Best regards,
Frans Maes


Virusvrij.
www.avg.com

<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>

On Sun, Oct 22, 2017 at 7:36 PM, Patrick Powers <
patrick_pow...@compuserve.com> wrote:

> 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
>
> --
> ---
> https://lists.uni-koeln.de/mailman/listinfo/sundial
>
>
> ---
> https://lists.uni-koeln.de/mailman/listinfo/sundial
>
>
>
---
https://lists.uni-koeln.de/mailman/listinfo/sundial