Is there a name for the day on which the earliest sunset occurs? I know it
varies with latitude unlike the solstice.
Cheers,
John
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https://lists.uni-koeln.de/mailman/listinfo/sundial
Kevin,
I'm assuming you are not in North America as another important
happening is that there is a Total Lunar Eclipse on this Winter
Solstice. The last time this happened was 1638. More detail can be
found at http://science.nasa.gov/science-news/science-at-nasa/2010/17dec_solsticeeclipse/
I just received this email and thought I would forward it to the group.
I was on the tour mentioned but we covered a lot of ground and saw a
lot of sundials that day.
Cheers,
John
Begin forwarded message:
From: [EMAIL PROTECTED]
Date: August 18, 2008 6:59:54 PM CDT
To:
Greg,
Almost a month from now at the Autumnal equinox, Sept 23 this year I
believe, the sun will be on the celestial equator but the first quarter
moon (90 degrees from the Sun) will be 23.5 degrees plus minus about 5
deg from the celestial equator and thus below the horizon and will rise
With all the discussion of discs and holes I thought members might be
interested in some photos I took of tests we made when we were deciding
on the Gnomon for the Swensen Sundial. I have put them up on the web
page http://www.uwrf.edu/sundial/design2.html . I had hoped to have
them up a week
I liked your solution to the nodus problem as applied to the Swenson dial.
In reading about the dial on its web-site, I saw that great care was taken in
accurate placement of the dial's lines.
Could you please tell me how the declination of the wall was determined? I
think that if this
Theoretically it's correct that the projection of a circular disc on
to a flat surface parallel to the disc will be a circle.
Unfortunately the sun's apparent size results in the disc becoming
very blurred when you get a couple of hours off of local noon.
Luckily when we were building the
As a follow on from the Calendar questions from Frank Evans a few
weeks ago, there's something that's been niggling me for a while.
Someone on the list is bound to know the answer.
46 BC is widely reported to have had 2 extra months, and to have
been 445 days long, to make things ready for
I have an electrical question. My display table at Oxford will be a stained
glass sundial assembly table and I want to be able to use my soldering iron
and glass grinder that are both 120 volts.
The last time I went to England, I brought the wrong power converter. They
sell five or six
University System so , starting Fri, 4:30 PM until sometime Sun or
Mon, expect no new pictures from the Swensen webcam.
-
On my G4 Mac, I don't see any popup windows using either Netscape
7.01 or Internet Explorer 5.1. I do have JavaScript enabled.
-
reading his first email correctly. I was guilty, as Profs. often are,
of thinking the question was something we have heard many times and
answering that and not what was asked. I also had made a quick
incorrect calculation in my head and as the answer was the same as
Willy's used that. To
Thank you Piero and John.
But after your answers my problem remains.
1.
The equation of time can explain no more than about 31 minutes. The difference
I descirbe is 21 hours and 10 minutes.
2.
I describe a difference between two parts of the elliptical orbit of the earth
which are
The spring equinox was about at 3-20-2002 18:50 UT
Midsummer is about at 6-21-2002 13:10 UT
The autumn equinox is about at 9-23-2002 04:40 UT
The difference between the time from spring equinox to midsummer on one
hand and the time from midsummer to autumn equinox on the other hand is
Art Carlson
Wrote:
(snip)..
Given the key word
heliacal rising, I have been able to find the definition and some
discussions on the Net. I find it surprising that this could be, as
John Sheperd said, pinned down to a single day. Wouldn't this
depend on the brightness of the star and the
Unless he's an Astronomer his watch will be running on Solar Time and so it
will be noon standard time and the sun will in the same place except for
the equation of time correction.
If, however, the watch is running on Sidereal Time, which only Astronomers
use, after six months he will be off 12
I'm happy to report that the Swensen WebCam
http://www.uwrf.edu/sundial/Webcam.html is up and running again. I still
have to get in and adjust the camera mount and zoom but pictures are being
taken again. We missed Beltane but the Summer Solstice is still to come:-)
Cheers,
John
Just a note on Robert Terwilliger email, I have generated hundreds of plots
and plot files:
(snip)
1) Huge file size.
This is no doubt caused by producing a representation of an analemma or
other object that includes a large number of points. Not only will this
create a huge file, but it
In reply to John Davis:
I have a question/challenge to all you sundial designers: what is the most
accurate design for a Standard Time dial?
My vote is of course for a dial with the EOT built into the hour lines to
give the annalema shapes such as used in the Swensen Sun dial at :
As a Physicist who grew up in England I learnt both systems. When I came to
the USA with its decimal monetary system (England was still on the old 240
pennies to the Pound) I learnt an often un appreciated virtue of the
British System. The first time I went to tutor an inner city kid he asked
me
Some of you may have noticed the Swensen Sundial Web Cam at
http://www.uwrf.edu/sundial/Webcam.html has been down longer than normal.
The trouble is we've recently undergone a massive Network upgrade plus
several major hacker attacks which are all handled by the same person. The
server that
Sod's Law or Murphy's Law is still in operation.
As soon as I decided it was about time to say something about the web cam
being down I am informed its back up! You can see its a nice sunny day at
River Falls at http://www.uwrf.edu/sundial/Webcam.html even though its
below 0 degrees F.
Cheers,
John Carmichael wrote:
My new Celestial Products moon calendar says that there will be a total
lunar eclipse at 4:41 UT on January 21 (the evening of Jan. 20th in North
America).
We have already discussed on the list the fact that moonlight should
indicate the correct time on a sundial during
Concerning [EMAIL PROTECTED] and [EMAIL PROTECTED] comments on christmas
and the start of the Year my information is as follows:
When Julius Caesar reformed the calendar in 46 BC the traditional dates for
tthe Vernal equinox was infact March 25th and the Winter Solstice December
25th. In his
A quick answer to Arthur Carlson question,
Ranger George seemed to think that the expectations that the Earth was
smaller greatly inhibited the discovery of the actual size. The ancient
Greeks had believed in a rather small value, and who could question their
authority? It was also an important
Further to Roy Anthony's note on laying out a large dial.
His method is similar to the one used for the Swenson dial which is 30 by
60 feet. An arm with a scale attached was pivioted at the base of the
gnomon. This was the origin of the original x-y set of points defining the
dial lines.
My favorite way to show eclipses and sunspots is with a reflective pin hole
camera. A small mirror, preferably front surface, about .25 to .5 inches in
diameter mounted on a camera tripod. The light from the sun is reflected
through a window into a darkened room onto a white wall or screen. Its
Dieter Fredra wrote:
About a year ago I heard about an Internetproject. The goal was to use
webcams to display actual pictures of several sundials from all over the
world. The idea behind was to give a help in order to better understand
the concept of time at the same time, sundials shows
Dave,
I'm looking for ideas on field-aligning a polar mount for cameras and/or
small telescopes. I will be travelling to Europe this August for the total
solar eclipse (see - sundials won't work!), and will be bringing along a
portable tracking camera mount.
My first reaction is why all the
Slawomir K. Grzechnik wrote:
2. Paris meridian, or rather opposition to Greenwhich Meridian, was still
seriously raised on international conferences before the First World War.
French lost the Prime Meridan finally but won meters, liters and kilograms,
very useful BTW, not yet in the US. In
Thanks to Tom Semadeni for his kind words:
Thanks to Chris, for the clever graphical explanation showing especially the
discontinuities which support his recommendation to look at John Shepherd's
work on the beautifully designed and executed Richard D. Swensen Sundial
at the
University of
Here is a copy of the letter I sent to Rory, who contacted me through my
web page (http://www.uwrf.edu/sundial/), before the letter from Jack Aubert
was posted.
Cheers,
John
Rory,
I am sorry to have taken so long to reply but I have a couple of deadlines
to make.
Your question is an
Sorry to use up valuable band-space but I got an e-mail request for
information on the Swenson Sundial from Gary Frazier at Texas Instruments,
Dallas. My reply to his email address bounced.
The dimentions on the Sundial are:
Gnomon Length: 56.5 horizontal 79.7 ploar length. The area of the wall
Fellow Gnomonists,
I've just completed a major update of the Swensen Sundial page at:
http://www.uwrf.edu/sundial/welcome.html
I've included a lot more images and diagrams. Take a look and let me know
if you spot any problems.
Cheers,
John
Professor John P.G.Shepherd
Physics
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