https://www.brown.edu/news/2019-05-08/sundial
--
---
https://lists.uni-koeln.de/mailman/listinfo/sundial
Depending on your choice of rotation axes, only two rotations are
needed, one for the elevation of the pole and one around the gnomon for
longitude correction. These are the two that correspond to the actual
changes needed.
If you are using the three orthogonal x, y, and z axes, then three
Assuming that a dial should read only local solar time is a rather
limited view. While it might be of interest to the dial purist, it is
not particularly useful to the general population and often requires a
lot of explanation. And it makes us seem like an eccentric clique. The
dial produces a
Rotating the dial plate around a vertical axis is wrong because the
hours lines are not at constant angles.
Rotating the whole dial around the polar axis is the correct way to
adjust a local solar time dial to a different longitude, the time zone
center, for example.
Having a dial show the
Steve tells me that the lack of longitude correction instructions was
due to my choice of 'local solar time' as the time indication. When I
use 'UTC-5' I get the instructions.
---
On 2023-04-02 21:30, kool...@dickkoolish.com wrote:
I tried the app. I used 40, -75 and 45, -70. It just said to
I tried the app. I used 40, -75 and 45, -70. It just said to use a 5
degree wedge and said nothing about a longitude correction.
I communicated to Steve privately last week. I said that a longitude
correction was a rotation around the gnomon. Does anybody else believe
this? One of the books, I
Stenopiac image just means pinhole image.
While pinhole images can look fairly sharp, they can't match the
sharpness of a lens. The optimal pinhole for an 8x10 inch camera can
resolve about 5 lines per millimeter, which will look sharp as a contact
print. A good lens can resolve 100 lines per
You might look here and see if anything helps.
http://www.moonstick.com/
---
On 2020-02-04 09:48, David Benton wrote:
So I’ve been trying to find detailed information on Moondials and how
to make them. Unfortunately, I’ve not found much out there on the
subject.
Does anyone here in our
This might be of interest to dialists.
https://www.theguardian.com/science/2019/aug/30/compasses-to-point-true-north-for-first-time-in-360-years
---
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Didn't Eratosthenes show that the earth was round by measuring the
diameter?
- Original Message -
From: "Dan-George Uza"
To:"Sundial List"
Cc:
Sent:Mon, 17 Jun 2019 16:04:58 +0300
Subject:Can a sundial disprove Flat Earth?
Hello,
In my country there is this growing Flat Earth
A friend asks if the dates where the north and south going branches
of the analemma cross have a special name. Around mid-April and the
end of August.
---
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This was sent to me by a friend.
https://www.panorama.am/en/news/2019/02/23/Armenian-sundials/2076856
---
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This dial tells you that it is the solstice.
https://apod.nasa.gov/apod/ap170621.html
---
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18% gray is used because that was thought to be the average
reflectance of photographic subjects.
- Original Message -
From:
"Patrick Vyvyan"
To:
"John Lynes"
Cc:
"sundial list"
Sent:
Sun, 26 Feb 2017 13:01:10 -0300
Something else that happens twice a year is MIT Henge.
http://www.dickkoolish.com/rmk_page/mithenge.html
- Original Message -
From:
"Art Krenzel"
To:
"sundial@uni-koeln.de"
Cc:
Sent:
Wed, 18 Jan 2017 22:41:15 +
Subject:
Unusual
Of course the first analemma picture was taken by Dennis DiCicco.
http://twanight.org/newTWAN/photos.asp?ID=3001422
- Original Message -
From:
"Robert Terwilliger"
To:
Cc:
Sent:
Wed, 21 Dec 2016 08:43:28 -0500
Subject:
Astronomy Picture of
In Boston MA USA, today was Evacuation Day, which
celebrates the evacuation of British troops from
Boston during the Revolutionary War. :-)
https://en.wikipedia.org/wiki/Evacuation_Day_%28Massachusetts%29
---
There's a Wikipedia article about leap years.
https://en.wikipedia.org/wiki/Leap_year
>
> Frank,
>
> Why have you sent your wishes for a Happy Leap Year Day on February 24 ?
>
> Willy Leenders
> Hasselt in Flanders (Belgium)
---
The New York Public Library has put 187,000
pictures online. I don't know if there is a
top level text search, but if you pull up an,
image, there is a text search box at the top
of the page. So you can type in "sundial" and
see what images in the collection match.
Sorry, I forgot to include the link.
http://publicdomain.nypl.org/pd-visualization/
> The New York Public Library has put 187,000
> pictures online. I don't know if there is a
> top level text search, but if you pull up an,
> image, there is a text search box at the top
> of the page. So you
A student video showing how sunrise moves along the horizon.
https://www.youtube.com/watch?v=UzOkTjxhR3Q
---
https://lists.uni-koeln.de/mailman/listinfo/sundial
There was a recent discussion about moon phase
calculation.
Check out the slide rule and circular calculators at
http://www.moonstick.com/
---
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Here's an example of a dial with an equitorial band all around.
http://www.dickkoolish.com/rmk_page/sundials/phillips_andover.html
> On Mon, Sep 28, 2015 at 3:24 PM, Dan-George Uza
> wrote:
>
>> Hello,
>>
>> Tonight I saw the trailer for "The 100-Year-Old Man Who
"Turtles all the way down" of course. :-)
https://en.wikipedia.org/wiki/Turtles_all_the_way_down
> Beautiful dial and setting, Dick!
> But please explain for us:
> What's supporting all those turtles?!?
>
> Dave
>
> Sent from my iPhone
>
>> On Oct 1, 2015, at 3:53 AM, kool...@dickkoolish.com
> Mark Gingrich wrote:
> Indeed. And here's a curious bit of related trivia: If you
> start due east from *any* latitude and travel a great circle
> route -- i.e. "straight" -- a distance of one quarter of the
> Earth's circumference, you *always* end up on the equator.
>
> This also works from
At any point on the earth, there is one great circle that
is tangent to your latitude circle. That means that at that
infinitesimally small point, both circles point in the same
direction, i.e due east, but only at that point.
Also note that the plane that cuts the earth at any
latitude is
https://www.flickr.com/photos/suzanne-gibson/8377866276
Please help identify this architectural sundial and location recently
posted on Flickr.
https://www.flickr.com/photos/schraeglage-urbex/19116095082/in/explore-2015-06-24/
Larry Bohlayer
Sundial at the Very Large Array made from parts of an old
radio telescope.
http://news.stanford.edu/thedish/2013/10/02/worlds-first-radio-sundial-dedicated-in-memory-of-ron-bracewell/
---
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I saw the article today about some solstice alignments
at the Taj Mahal.
http://www.livescience.com/49660-taj-mahal-gardens-align-solstice-sun.html?google_editors_picks=true
---
https://lists.uni-koeln.de/mailman/listinfo/sundial
The declination of the sun around January 30th is
the same as on November 11th. So any alignments on
November 11th should also occur in late January.
For example, these are also the dates of MIT Henge,
where the setting sun shines down the 800 foot long
Infinite Corridor at MIT in Cambridge MA.
A simple rectangular projection where Longitude
is the X coordinate and Latitude is the Y coordinate
also has straight and perpendicular lines. And it
can go all the way to 90 North. Of course, longitude
is very distorted at the poles.
http://en.wikipedia.org/wiki/Equirectangular_projection
There are astronomy programs like Stellarium and
smartphone apps that give the azimuth of the sun
at a given time. That and a protractor will give
you true north.
I would also love to see sundials in schools. Not just an analemmatic
dials
but the multi dial as well.
This is why I am trying
Making sundials is easy compared to the
problem of writing software to keep track
of dates and times.
http://www.wimp.com/problemtimezones/
---
https://lists.uni-koeln.de/mailman/listinfo/sundial
A friend sent me a link to some information about a
large equitorial dial at the McCarthy Observatory in
New Milford, Connecticut. It does not seem to be in
the registry.
http://www.mccarthyobservatory.org/?page_id=163
http://www.mccarthyobservatory.org/?page_id=1197
The oblateness of the earth is about 1/298.
The Wikipedia page on the figure of the earth
is here: http://en.wikipedia.org/wiki/Figure_of_the_Earth
Here's another page on the shape of the earth:
http://en.wikipedia.org/wiki/Earth_radius
The WGS-84 ellipsoid gives the equitorial radius as
6378 km
While longitude lines are great circles, latitude
lines are small circles.
David Patte wrote:
Yes, at the point of intersection they are, but don't forget though that
lat and long are great circles, not straight lines.
Of course, there is no east or west at the poles.
This would be the starting azimuth of the great circle
route from your location to Mecca. Here's a web page
that does this: http://www.qiblalocator.com/
Douglas Vogt wrote:
Reminds me of someone a year or so ago who developed a method of
determining the east of Mecca for prayer purposes
There's another Paul Manship dial in Andover,
Massachusetts, USA.
http://www.dickkoolish.com/rmk_page/sundials/phillips_andover.html
Hi Mario,
Have a look at
http://www.1939nyworldsfair.com/worlds_fair/wf_tour/statues/fates_of_man.htm
for the amazing dial by Paul
There's another Paul Manship dial in Andover,
Massachusetts, USA.
http://www.dickkoolish.com/rmk_page/sundials/phillips_andover.html
Hi Mario,
Have a look at
http://www.1939nyworldsfair.com/worlds_fair/wf_tour/statues/fates_of_man.htm
for the amazing dial by Paul
Search Google Images for wrist sundial and you will see
this item and a bunch of others.
And there's always the Pocket Stonehenge:
http://www.ohgizmo.com/2006/06/19/stonehenge-pocket-watch/
Hi David,
That is a Fossil wrist sundial. The Fossil company, well known for their
watches, purses
Last November, Sara, Ken, Roger Sinnott and I visited
Wellesley College to check out the observatory and a
couple of sundials on the campus. The pictures are here:
http://www.dickkoolish.com/rmk_page/pictures_112312.html
Sara
Here are some pictures of the Paul Manship dial at the
Phillips Academy in Andover, Massachusetts, USA.
http://www.dickkoolish.com/rmk_page/sundials/phillips_andover.html
EXCELLENT!
From: sundial [mailto:sundial-boun...@uni-koeln.de] On Behalf Of Tony Moss
Sent: Monday, August 27, 2012
The commonly stated resolution of the eye is about
a minute of arc. The angular size of Venus during
the transit was just under a minute of arc, so it
would have been a difficult observation under any
circumstances. A minute of arc is about 1 inch at
100 yards, i.e. an American 25 cent piece at
This web page has some 3D pictures of the Venus transit
as well as some time-lapse sequences.
http://sweiller.free.fr/Venus/Venus-Transit.htm
---
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Here's an article from the Sky Telescope website
about the transit.
http://www.skyandtelescope.com/observing/home/Transits-of-Venus-Explained-152556885.html
Dear All,
As several have noted, there is a Transit of
Venus on Tuesday/Wednesday next week. For
those in the U.K. the 2012
Here's a New Yorker magazine cartoon about B.C.
http://www.condenaststore.com/-sp/There-I-go-still-writing-B-C-on-my-checks-New-Yorker-Cartoon-Prints_i8546253_.htm
---
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More information is here:
http://eclipse.gsfc.nasa.gov/OH/OH2011.html
I thought some of you might be interested in the upcoming lunar eclipse on
the 10th of this month. I've attached a diagram showing the regions of
visibility of the eclipse.
Brad
The problem is that the shape of the grid, as well as all the
geographic features depends on the map projection. See:
http://geology.isu.edu/geostac/Field_Exercise/topomaps/distortion.htm
To first order, you take a geographic object as a list
of lines between lat-lon points, use the map
I know some folks in the Antique Telescope Society who have
real, original Porter garden telescopes. Here's a photo
of two of them together:
http://www.dickkoolish.com/rmk_page/RMK_Pictures/D80-11-14-10/DSC_0147.jpg
Hello All,
Some of you may be interested in this if you have some spare
People might be interested in the book
The Sun in the Church by Heilbron.
It's about using meridian lines in
cathedrals for solar measurements.
http://www.math.nus.edu.sg/aslaksen/teaching/heilbron.html
Brent
If you measure the transit of a star (or any celestial body) through the
meridian
For eclipses to happen, the 'line of nodes' must be
aligned with the sun. This happens roughly every six months
and create the 'eclipse seasons' during which eclipses
are possible.
htmlHEADLINK rel=stylesheet type=text/css
href=/netmail/static/deg/css/wysiwyg-3933289048.css media=all
META
The equitorial drive of a telescope mount
also turns at the rate of the earths rotation
but in the opposite direction, so as to keep a
specific point in the sky in the telescopes
field of view. But you have different rates for
different kinds of objects and you have to
account for refraction.
The short answer is that any coordinate specification
has to be given in reference to a particular datum.
Here's the Wikipedia article on datums:
http://en.wikipedia.org/wiki/Datum_%28geodesy%29
Bravo, Tony Finch, for sharing this. I had no idea location was so
complex!
Thank you.
Mac
The date of earliest sunset depends on Latitude and is not
always Dec 14. See: http://www.idialstars.com/eass.htm
Dear Colleagues
In the depths of a freezing Northern winter, there's time to think about
days of special interest. There are six significant solar dates around
this time of
I've seen a United Parcel Service (UPS) TV
commercial that includes something which looks
like a possible sundial in the background.
Here is a shot off the TV screen. Sorry for
the poor picture quality.
http://www.dickkoolish.com/rmk_page/RMK_Pictures/Sundial_TV/DSC_0167.jpg
Try this experiment:
Draw a circle that represents the earth and
draw a vertical line through it for the
polar axis.
At 45 N latitude, draw the profile of a vertical
dial. At 45 S, draw the profile of a horizontal
dial. You will see that they are in the exact
same orientation with respect to
Here is one of the Porter sundials in Springfield VT.
http://www.dickkoolish.com/rmk_page/RMK_Pictures/S60-07-31-06/IMGP0754.JPG
Friends,
Is there a conventional name (like horizontal', equatorial', polar' and
so on) for the sundial constructed as shown below?
Am I right thinking that
The problem with all these arguments is that they
assume that all hours of the day are equally useful,
and they obviously are not. A sarcastic or funny
joke doesn't change the fact that most people today
have more waking hours after noon than before noon.
Hi
2010/3/16 Chuck Nafziger
Even if the myths are busted, some people
still like it. Most of our lives are not
symmetrical around noon, but are biased
to the afternoon and evenings, so having
more daylight then is a better match for our
daily activities. In Boston, the summer solstice
sunrise is at 5:08 AM. That's two
The position of the pole isn't constant anyway.
Here is the Wikipedia article on the Chandler wobble.
http://en.wikipedia.org/wiki/Chandler_wobble
And here is a photo of the Chandler tombstone in
Cambridge MA.
http://www.dickkoolish.com/rmk_page/RMK_Pictures/Astronomers640/SChandler.JPG
I also
There is a Java applet showing the effects of refraction
and flattening at:
http://www.jgiesen.de/refract/index.html
If it came from this list originally, I apologize in advance.
---
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Theater lighting gels are plastic sheets that
come in a large variety of colors and are inexpensive.
I don't know if they will stick to windows or would
work in a computer printer. Rosco is one of the major
brands.
---
There are a lot of navigation calculations at:
http://williams.best.vwh.net/avform.htm
It includes the distance and course between points.
---
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An original Porter Garden Telescope recently sold at the
Skinner auction in Boston.
http://www.dickkoolish.com/rmk_page/pictures_032207.html
There a couple of Porter sundials in the telescope making museum
at the Hartness House in Springfield VT.
Here is a sundial at Mt. Auburn Cemetery in
Cambridge MA, USA.
It's probably not a cremation container, but certainly
could be.
http://www.dickkoolish.com/rmk_page/sundials/payson_mtauburn.html
Hi all,
Was having a look at Google Patents using the key word sundial and =
found a number
Two moon phase calculators that do exist are at:
http://www.lunawheel.com/
http://www.moonstick.com/
Dear sundial friends,
To celebrate the solar eclipse tomorrow, I prepared a DeltaCad macro for
finding the MEAN MOON PHASES.
All callendar constructions use somehow corrections for
I put some pictures of the Kennedal Sky Pointer on a web page at
http://www.dickkoolish.com/rmk_page/pictures_032306.html.
Sky Publishing used to sell them. You can set the RA and Dec
of an object and the date and time and it will point to the
position in the sky. Or you can set the Dec and
day, the declination of the moon changes a lot every day,
since it goes through the cycle from maximum to minimum
declination every month, while the sun takes a whole year
to go through that cycle.
Yes, I knew that. And I heard as well that the moon's
extreme declinations vary from
On March 20, the declination of the sun is 0, so it rises
due east and sets due west. The moons declination on that
day is almost -26 degrees so it rises south of east.
The full moon rise this past Tuesday was almost due east.
Unlike the sun, whose declination changes just a bit every
day, the
See: http://www.mreclipse.com/Totality/TotalityCh11.html
This is from Fred Espenak at NASA.
http://www.mreclipse.com/Totality/TotalityCh11.html
-
http://pollux.nss.nima.mil/calc/degree.html
this page will compute the size of a degree of
latitude and longitude
-
I've been given an Aquitaine ring sundial. I'd like to
know how to compute one, but have been unable to
find information in my sundial book collection or
on any sundial web sites.
-
For pinhole imaging, the optimal diameter of a pinhole
is one where the pinhole is the same size as the
diffraction disk it produces.
There is a calculator at:
http://www.mrpinhole.com/calcpinh.php
and a lot of information at:
http://www.pinholeresource.com/pinhole.html
-
Amateur astronomers also deal with polar alignment when they have to
set up an equitorial mount. This is usually done with a low power
finder scope (6 to 8 power). If you can attach a finder scope to the
sundial, this would be much better than trying to align by eye.
Some finder scopes just
There's a pinhole camera photo of the Portland Oregon Union Station sundial
at: http://web.pdx.edu/%7Eharveyt/C1.html
Don Yeier, ex Vernonscope owner is having a scientific instruments auction
on Saturday, May 19, 2001, in Candor, New York (near Binghamton). In addition
to antique telescopes, binoculars, clocks, etc. the flyer says there is an
Augsberg equitorial dial and other sundials. Catalog is $20.00
The photo-3d list people maintain a different list sell-3d for
commercial postings.
Actually it is dark, but the lights are on. See the amazing photo at
http://antwrp.gsfc.nasa.gov/apod/image/0011/earthlights_dmsp_big.jpg
Daniel Wenger
We amateur astronomers call that 'Light Pollution'.
http://www.darksky.org/ida/index.html
There's a web page on rainbows and halos at:
http://ds.dial.pipex.com/lc/atoptics/phenom.htm
From the web page:
http://sunearth.gsfc.nasa.gov/eclipse/SEhelp/SEgeometry.html
Eclipse geometry is complicated by the fact that Earth's orbit around the Sun
is elliptical. As a result, the Sun's apparent semi-diameter varies from 944
arc-seconds at aphelion to 976 arc-seconds at perihelion.
Take a look at this sundial:
http://www.angelsandearthlythings.com/hp4500.html
I think it has problems. Am I correct?
Thomas Harvey posted a picture to the pinhole photography mailing list
of a sundial in Portland Oregon.
http://web.pdx.edu/~harveyt/USsundialPin.jpg
There's an 8 page article about sundials in the July/August issue
of Weatherwise magazine.
People on this list may be interested in the Moonstick
slide rule moon phase calculator.
www.moonstick.com
The cover of the June 2000 issue of Embedded Systems programming has
a sundial with the gnomon pointing in the wrong direction. I've already
emailed them about it.
It's on my web page at:
http://linux.bbn.com/~koolish
with the full scan in:
http://linux.bbn.com/~koolish
Isn't Beltane the other side of Candlemas?
I am looking forward to an authoritative answer based on solar declination.
Roger Bailey
Beltane explanation (and other cross-quarter days):
http://www.isleofavalon.co.uk/edu/g-bank/articles/beltane.html
The normal procedure when photographing the sun is to use
a neutral density filter of density 5.0, which reduces the
light by a factor of 100,000. So even of you took a picture
a week through this filter, it's nowhere near the exposure
needed to register the foreground image.
There is an article in the most recent edition of Sky and Telescope magazine
about photographing the analemma.
It describes how photos have been taken which show the movement of the sun.
They rely on time lapse (either 365 or 12 exposures over the course of a
year), with each exposure
The eye/brain is very good at seeing lines, and can see lines thinner
than the usual 1 arcminute given as the resolution of the eye.
20/20 vision is based on reading letters that are 5 arcminutes high
that have 1 arcminute features (line width and gaps). So this might
give you an idea of how big
The synodic month (full moon to full moon) averages 29.53 days, while
the anomalistic month (perigee to perigee) is 27.55 days, so the phases
drift with respect to perigee.
see: http://www.treasure-troves.com/astro/AnomalisticMonth.html
There's a great web site for eclipse info, both solar and lunar at:
http://sunearth.gsfc.nasa.gov/eclipse/eclipse.html
A page of solar filter sources is:
http://umbra.gsfc.nasa.gov/eclipse/970309/text/filter-sources.html
There's a page of books on atmospheric phonomena at:
http://www.treasure-troves.com/astro/AtmosphericPhenomena.html
One book that I like is:
Greenler, R., Rainbows, Halos, and Glories,
Cambridge University Press, 1980.
A paper recently put on the web about pinhole photography has a section
about something called a 'Pinspeck Camera' that might have the same
properties as the bead in the hole shadow sharpener.
See: http://www.pinhole.com/resources/articles/Young/index.html
and look down near the end of the
Patrick Powers wrote:
It is simply the pin hole camera effect again. Light passing through any
small aperture is focused . As the hole's size is changed the focusing
parameters are changed too. So with a fixed distance from hole to plate
there will be one size that works. A different size
I've put a picture of what I think is a sun tracking device on my web page at
linux.bbn.com/~koolish. If anybody has seen one or knows how it was used, let
me know. There are no markings on it.
A web search turned up glass spheres at:
http://www.angelsandearthlythings.com/s-sphere.html
Somebody was interested in the Sundicator. I've got one.
I scanned the Sundicator and put an image on my web page:
http://linux.bbn.com/~koolish
Click on the small image to get the big image (296K).
We are coming up to the day when sunset lines up with the Infinite Corridor
at MIT (Massachusetts Institute of Technology) in Cambridge, MA, USA.
I may try and observe it this year.
http://w3.mit.edu/afs/athena.mit.edu/org/p/planning/www/mithenge
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