Hi Gordon and mirror folk,
I just thought that someone might know the oil they use to cover the
mercury with so that it could be experimented with in the ceiling
sundial situation in order to have a safer flat, level mirror. But
thanks for the info, that is interesting. I've visited both
Fred,
A place to start should be:
www.monticello.org/press/sundial.html
Best,
Bill Maddux
Received the following today. Can anyone help Scott Vincent? Reply to
[EMAIL PROTECTED]
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Dear Mr. Sawyer:
Can you direct me to the artisan who reproduced
Thanks, Fer. Apologies all round, and especially to
Anselmo. I now think his proposal would work after all. But only in
the winter months. At noon at the equinox the reflected beam would be
vertically above the mirror. During the summer months the beam would be
reflected south of the
Hi John,
I agree that some leveling surface like your idea of a mercury pool
with the mirror on it would easily give a very level mirror for the
traditional ceiling dial.
Again, using a container large enough that the area for the mirror is
free of meniscus is a good idea.
Since we were
Dear Diallists,
I have been researching the history of two vertical sundials on the
south-eastern buttress
of the 17th c. chapel at Wadham College, Oxford and wonder if any of you
have come
across any reference to them. The College authorities are interested in
restoring them.
All that remains
hello every body, in an ancient book called roret de l'horloger
rhabilleur a simple method is described for obtaining the meridian inside a
room with a window facing south.
First, you have to determine the meridian outside on the principle of a
horizontal dial allowing reading of the solar noon
John Carmichael suggested floating the mirror in mercury to level it, and
then Dave Bell pointed out that the clean surface of the mercury could be
the mirror.
Since mercury is a bit of a problem to work with, could a dish of water
serve instead? In John's case, he just needs the mirror to be
John Carmichael contributed:
But something tells
me that even this method could be riddled with errors. (i.e.. what if you
give ZW2000 the wrong information because your measurement of the ceiling
height was 2 mm. off? Or, will the glass cover on the floating mirror
refract the sunspot?)
I
I thought I might share a simple drawing (URL below) that illustrates
Anselmo's idea. In the drawing the Sun is on the Equator so the angle
of the Solar rays onto the respective surfaces (polar dial plate and
ceiling) is 90deg. However, it can be seen that this relation holds
throughout
Hi John,
There are several limitations to concider but the
principle still is true.
The problems you mention occur at
latitudessmaller then47 degrees.
The max. altitude of the sun h = 90 - phi + 23.5
degrees.
The inclination of the mirror i = 0.5
phi
We search for the latitude where
Hello Tony:
Starting a couple of days ago my monitor has gone into the power saver mode at
random times and the only way to recover is to reboot.
The screen is black and the power light changed from green to yellow. The
problem only occurs during browsing and most frequently during operations
More information on mercury liquid mirror telescopes.
Mercury mirror with Mylar film overlay
http://www.abc.net.au/science/k2/moments/s64751.htm
On one web page automobile motor oil was suggested in lieu of mercury. I
have not been able to find the overlay liquid used by the Canadian
Hi Luke,
I copied your drawing and I am glad you made a drawing for a latitude
lower then 47 degrees.
I added in red the sun's beam at noon at summer solstice and you may see
that the beam is reflected in the wrong direction as John wrote.
The grey line between is the normal to the mirror's
Hello Fer,
I made the drawing for my Lat (approx. 36 degs.) and was able to notice
that for my location a complete coverage couldn't be obtained but I
hadn't gone further to find where (or if) this limitation disappears, so
thank you for doing so. The image you sent says it all, this has
On Sun, 6 Jan 2002, fer j. de vries wrote:
The max. altitude of the sun h = 90 - phi + 23.5 degrees.
This reminded me of something I saw recently, that was a bit of a puzzle:
I live at 37.3N latitude. This puts the mean plane of the Ecliptic at
something like 52.7 degrees elevation. Near the
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