Dear Fer,
Thank you for your message. Your procedure
is almost exactly like mine. I also start
with the equatorial plane (I missed that
step out in my message). I then:
1. Rotate by phi (to make the plane vertical)
2. Rotate by Azimuth (to face the plane in the
Dear All,
The beer-glass sundial spotted by Mike Cowham brought
on a panic attack. More strictly, it was his comment
that caused alarm...
The glass acts as the gnomon but the real horror ...
midday was at VI.
Maybe every reader should pour a glass of beer (or
something stronger) before
Dear John,
That is a great dial. I really must look
into this glass-based colouring that you
use. I can testify to its durability.
The six dials on the Gate of Honour at
Gonville and Caius College are made with
this technology and their colours look
almost as good as new after the better
part
Dear Tony,
You say...
I shall be staying near Brescia in Lombardia...
One thing you can do is to visit
http://www.sundialsatlas.eu
You then click on the map button at the top and,
by dragging the map and zooming, home in on Brescia.
Alas, there are no sundials shown in
Dear Reinhold,
Your news is good news...
The Italian sundial catalogue
announces 24 sundials for Brescia!
My news is bad news...
Alas, there are no sundials shown
in Brescia itself...
I think I should have punctuated my
remark differently and added a t:
Atlas: there are no sundials
Dear Fabio,
You mention some reflection sundials...
In the Convento di San Cristo you can find a
reflection sundial...
In Italy there are other four ancient reflection
sundials ... in the provincia ... of Bergamo, beside
the Brescia one.
... another one is in Palazzo Spada in Rome...
Dear John,
I'm asking you guys if you have seen any
relationship between owls and sundials.
I once tried very hard to establish such a
relationship but my best intentions were
not appreciated...
I had a client and I wanted to symbolise
sunrise and sunset on the proposed sundial.
I offered a
Dear John (and Willy, Aleks, Wolfgang, et al),
I have greatly enjoyed the all the answers
to your question about Owls and Sundials...
Willy Leenders tells us that the Dutch word
zonnewijzer really means wiser sun. How
many of us knew that?
Aleks has sent us a nice illustration of a
sundial
convincing, but there is
something horribly wrong with the
gnomon!
Last summer the Hughes Hall May Ball
supported the World Owl Trust and two
owls were present as guests.
Frank King
Cambridge, U.K.
---
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cast a straight-edge
shadow :-)
I suspect that the writers of this browser are
not NASS members!
As you rightly say:
Why this name was chosen is not clear.
Maybe someone should try using the browser!
Frank King
Cambridge, UK
---
https
a disappointment.
Either, at the critical moment on the
critical day, the sun isn't shining or
on a quite different day the sun happens
to be in the correct direction and spoils
the story.
Frank King
Cambridge, U.K.
---
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College
but this is proving challenging too. There weren't
many women's colleges in those days so I may have
to search each one in turn.
If anyone has any leads please let me know.
Frank King
Cambridge, UK
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Dear Fred,
As usual, your encyclopedic knowledge has
come up with a couple of nuggets!
http://tinyurl.com/2fpvfah
http://rfrost.people.si.umich.edu/courses/MatCult/content/bladerunner.pdf
These are fascinating and most helpful.
Very many thanks indeed.
Frank
Dear All,
Fred Sawyer notes a plea to President Obama
to have a sundial which was originally in
Hawaii, but is now in Maryland, returned to
its rightful place:
http://www.congress.org/congressorg/bio/userletter/?letter_id=6195591101cont
ent_dir=politicsol
If President Obama is successful,
Dear Wolfgang,
You have come up with some most interesting
references to Kathleen Wright (née Higgins).
At last we know her Oxford College, Lady
Margaret Hall.
I enjoyed your calculations that lead to her
being born in 1926...
Died 1 January 1999 aged 72, therefore...
Since she died on 1
Dear Woody,
This is indeed good news...
http://www.gcstudio.com/suncalc.html
is back working.
I too made much use of GC Studio and greatly
missed it while it was down. As Bill Gottesman
suggests, it must have been off-air for a year
or more.
This is the great snag about the Internet...
almost nothing about iPhone camera
technology and cannot give a convincing
explanation of the physics behind this
artifact.
There is also the surrounding elliptical
red background to explain. Could that be
an image of the hot front surface of the
lens?
Any thoughts?
Frank King
Cambridge, U.K
Dear Tony,
Just to lower the tone a bit more...
I have a colleague who comes from Copernicus's
home town of Torun. Whenever he is asked about
his ethnicity he always says I am a North Pole.
All the best
Frank
---
Dear Brent,
You correctly note...
It looks like the date must have changed at noon.
Indeed so. Interestingly, even with GMT (as used by
astronomers and navigators) the date used to change
at noon (which was referred to as 0h GMT). This was
the case until 1 January 1925, so not very long ago!
Dear Andrew (and Fer),
Many thanks for this reference...
http://www.aandc.org/research/nautical_time_and_date.html
That is a splendid article and shows just what pitfalls
one can fall into when attempting to force historical
data to fit the present way of thinking!
I share your thought...
Dear Roger,
As your reference to French Revolutionary Time
says:
The hundredth part of the hour is called
decimal minute; the hundredth part of the
minute is called decimal second.
With 10 hours in the day (one mean Earth rotation
with respect to the sun) this gives:
10x100x100 =
Dear Richard,
You refer to a Portuguese communal flag...
This is the only example I have seen of a
sundial on a flag (combining two of my
interests) - are there any others ?
You might look at the Portuguese National
Flag which has an armillary sphere as its
background. See:
Dear Frank,
You say:
I have not come across an altitude dial
resembling an analemmatic dial in that the
gnomon is moved with the seasons and the
time curve is a single ellipse.
One interpretation of what you seek is to
have a dial on a vertical wall where the
gnomon is horizontal (and
if they are built on a vertical wall.
Nevertheless, I think the sundial that Frank Evans
wants IS an Analemmatic Dial on a Vertical Wall.
He wants an elliptical hour ring and so on.
Perhaps he will tell us all soon!
Frank King
---
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what projection is used.
Can James Morrison comment please?
Frank King
Cambridge, UK.
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Dear Marcello,
Several members of this list have been discussing
the Brazilian National Flag privately. We would like
to know how accurate it is!
The best article I can find is in:
http://www.zenite.nu/04/0804.php
The key paragraph is:
Adotada em 19 de novembro de 1889, seu
Dear Marcelo,
Many thanks for your reply...
...the republic was officially proclaimed
(signed) at 8:30 am on 15 November 1889
That is very impressive. Most people I
know are hardly awake so early in the
morning.
Methinks it [sidereal time] is mentioned
in the legislation to avoid
Dear John,
I really enjoyed your analysis distinguishing the
standpoints of British and U.S. diallists when it
comes to longitude-corrected dials. I need to
send two replies. Here is the first...
In the U.K. most of us are indeed fairly close,
in time, to the Greenwich Meridian. I am about
26
Dear John,
Your inspiring message about longitude correction
prompts more thoughts from me. You say:
... most of our [US] Time Zones have wiggly
irregular boundaries that sometimes span
distances far greater than 15 degrees.
Everyone necessarily lives within 7.5 degrees of
a multiple of 15
Dear John,
That is a fascinating map...
http://www.travel.com.hk/region/timezone.htm
It bears out many of my prejudices and gripes!!
Alaska seems to be a whole time-zone wrong and
John Pickard's eloquent contribution draws
attention to the curious way that Australia
is carved up.
One
Dear John,
I looked into your interesting assertion about
the Equation of Time. You say:
On the average, it is only off [mean time]
by about seven minutes...
It isn't really appropriate to use the term
average here because we are not dealing with
random variables or errors. We are just
Dear John,
I sympathise...
I flunked statistics in college.
I never got the hang of statistics until I
was fingered to give a lecture course on
the subject and I have never looked back!
In dialling, I use statistics for error
analysis and also when trying to do things
which are impossible!
Dear Brent,
You have started an interesting train of
thought. You, and others who have replied
to you, should dig out the February 2011
issue of Scientific American and read the
article:
How Language Shapes Thought
This is subtitled:
The languages we speak affect our
Dear Jackie,
That is an interesting observation...
... I moved from London to Brighton...
In London it seemed usual to say it's on
the left of the street, but here on the
coast, far more people say it's on the
east side.
Next time I am in Brighton I shall test the
natives.
The natives
Dear Claude,
Those are fascinating pictures especially:
http://www.gallerydiabolus.com/gallery/upload/utisz/my%20sun%20and%20your%20s
un3.jpg
This is almost straight out of M.C. Escher!
You ask:
What's the declination of that wall?
That's a fun question. As with many Escher
drawings the
Dear Willy,
I am not very familiar with the Prague
clock and I am confused by the recent
messages. You say:
... the clock indicates now Central
European Time rather than solar time
as it once was...
This suggests something far more radical
than simply setting the clock for the
wrong
Dear Jim,
I am grateful to you, and to Willy and Geoff,
for various points of clarification. The key
point in your comment is:
A hand with a Sun figure rotates once in
a mean solar day...
This at once distances the clock from an
astrolabe where, properly set, you look at
true solar time
Dear Brent,
You ask a fascinating set of questions.
Has the leap year problem been solved with
solar calendars?
At one level, the problem is intractable. You
get defeated by the calendar bequeathed to us
by Pope Gregory XIII...
The problem is that the Gregorian calendar is
hardly an
Dear Brent,
Slight goof. In step 7 I meant to say:
7. Keep going until 12 noon on 29 February
next year. You will have drawn EXACTLY
366 little lines. [Note that 29 February
is 365 days AFTER 1 March the previous
year, not 366 days.]
You have 366 lines and 365 normal
Dear Andrew,
Thank you for your two messages, sent off-list but my
response may be of trifling interest to others...
It is true that 128 tropical years is very close
to 46751 days but when it comes to a real solar
calendar (one you can look at and say Oh, I see
that today is 9 March) I regard
Dear Brent,
I understand your excitement...
In my excitement I forgot that solstice
to solstice is not one year but only one
half of a year.
But is isn't :-(
The best you can say is that it is ABOUT
half a year. The Earth doesn't have a
circular orbit and the solstices don't
coincide with
Dear Roser,
Willy Leenders is quite right that...
PERIGEE is the point in the orbit of
the moon or a satellite at which it
is nearest to the earth.
BUT...
Strictly, this is when the centre of the
moon is nearest the centre of the Earth.
YOU are unlikely to be at the centre of
the
Dear Reinhold,
I see you are trying to provoke me...
Frank King will tell us perhaps a nice
sounding Latin expression?!
This is the worst day of the year for me,
truly...
Dies irae, dies illa...
The day of wrath, that day... :-)
Or, perhaps, you seek my thoughts on whoever
first
sundial when
you can stand up straight and look at your own shadow?
Frank King
Cambridge.
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Dear John
You write...
How in the world did your local Education
Authority reach the absurd conclusion
that interactive human analemmatics are
dangerous for children.
Have you never heard of the expression about
being afraid of your own shadow?
This is a well-known phobia which has to be
Dear John,
That looks to be a monumental achievement
in several senses!
http://www.flickr.com/photos/jlcarmichael
Judging by the photographs, you could have
set this up with any orientation you liked
so some questions:
1. Why did you choose to have it facing
south-west? [Do the
Dear John,
Many thanks for the follow-up. I now
have a heap more questions!!
In your drawing you have half-hour dots
and quarter-hour tick-marks. In the
photographs, I can't see the tick-marks.
Is that my poor eyesight or did these
get lost as a budget-saving measure?
Also in the drawing, you
are Fabio's alignment hours.
Frank King
Cambridge, UK
---
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that faces south and so on.
I have a final piece of advice...
If you really want to drill lots of holes
at awkward angles you are going to need
some kind of jig. I cannot think of a
good way to design this jig but I am sure
there are other list members who can help.
All the best
Frank King
Dear Kevin,
I was interested in your comments on EoT.
I agree that the kidney curve is not very
pretty. You would be happier if we could
go back to the year 1246 when the analemma
had mirror symmetry about its long axis.
This would tidy up the kidney a little!
You say...
...the master of all
Dear Chris,
As always, you prompt further thought...
Gears, although limited to an integral number
of teeth, are essentially analogue devices,
aren't they?
Er, not sure :-)
In earlier days, I spent many a happy hour
looking at clocks and counting teeth. That
felt like a digital experience
Dear Brent,
You note:
The people who live in the tropics have
another special event, when the sun is
directly over their latitude.
This is not quite true unless you go to
an enormous amount of trouble. If you
live in the tropics, what normally happens
is that the sun crosses to the south of
Dear Frank,
I enjoyed your message about determining your
position when the sun is close to overhead.
Your theory is sound and I certainly cannot
compete with your practical experience but
something bothers me...
You measure the sun's altitude assuming
it is within a few minutes of arc from
Dear John,
Yes, Eratosthenes was a great man who is
also noted for his sieve for extracting
prime numbers.
This may not be the right list for asking
about the performance of camels but I am
intrigued that it took a camel 50 days to
travel from Aswan to Alexandria.
The straight line distance is
Dear Brent,
I think your proposals should be examined by
the Organisation Overseeing Orbital Parameters
(OOOPs). They would note:
I might move the moon closer to the earth
to create better surf.
Indeed it would. Total eclipses would last
longer too.
Think of all the unfortunate people
Dear John,
You are not wandering too far off topic...
I used to train architectural students to
pace a metre accurately.
When I take a party on a local Sundial Walk
I always start off by congratulating them
on each bringing along their own sundials.
I ignore their blank looks and explain
Dear Frank,
I must read your reference...
I have a little book (A Manual of
Modern Navigation by S. M. Burton,
1941) with a chapter on the particular
case of very high altitudes.
The more I think about this, the more snags
I see. If I am very close to the sub-solar
point, and I try
Dear All,
We must assume that the tree casts shadows when
the sun shines! That keeps the topic relevant!
The topic was much discussed by 18th century
philosophers. The debate centred on the
Latin maxim Esse ist percipi to be is to be
perceived. If it isn't perceived then does it
exist?
Dear Roger,
This is all good fun. You note...
The underlying image of the sundial is clearly
for a 1755 sundial at 55°...
If you zoom in on the pelican version you can
see that the 55° turns into 53°. This squares
with the latitude of Eyam which is 53°20'.
On Patrick Powers's photograph
Dear Mike,
I see that Amazon are claiming that your book
A Dial in Your Poke about portable dials and
suchlike is currently unavailable. Can you
confirm this?
I am copying this to the SML in case anyone
else has wondered.
All the best
Frank
---
the world:
http://www.cacr.caltech.edu/futureofutc/preprints/18_AAS_11-668_Epilogue.pdf
Numerous contributors familiar to readers of
this mailing list sent in comments including:
Tony Finch
Rob Seaman
Patrick Powers
Frank King
and with enthusiasm!).
Enjoy your 2011 Christmas.
Now just what was it that was going on
2011 years ago?
Frank King
Cambridge, U.K.
---
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Dear John,
I like your story about the times quoted
by the Darwin control tower.
In some of my introductory talks about
sundials I mention Unequal Hours, Babylonian
Hours, Italian Hours and so on.
Just when the audience thinks this is offering
more choice than they can cope with, I explain
that
Dear Dave,
Hmmm. Hard to comment on this...
... Jesus was only 7 years old...
Given the absence of zero, 2011 years
ago takes us to 1BC. There is a little
uncertainty but current best estimates
of the date of birth seem to fall in the
range 6BC to 4BC which would make the age
between 3 and 5
.
Would any French, German or U.S. contributors
to this mailing list care to comment!!
Frank King
Cambridge U.K.
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Dear John,
You are right...
I think I recognise it as one of the
Connoisseur Sundials range.
Take a look at:
http://www.sundialsonline.co.uk/
You will see the very dial as the second
from the left. It is the same one right
down to the absence of screw heads!
But the bad (UK) news
Dynamic Time TD
GPS TimeGPS
Those who don't like UTC don't have to use it.
That's no reason for denying its use to those
who do want to use it.
Frank King
Cambridge, U.K.
---
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Dear Roger,
Sara's message merits serious study!
We here in Europe weren't totally asleep
in medieval times or even in the so-called
dark ages following the Fall of Rome.
[A fair proportion of Europe seems to be
falling asleep just now but that's not the
period you are referring to :-) ]
There
, while correct,
didn't sound right!
MORAL: when using Wikipedia be very careful;
read an entry in at least three languages
before making up your mind!
Frank King
Cambridge, U.K.
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Dear Roser,
You are right that checking Wikipedia entries
in several languages is interesting. They all
make mistakes!!
Spanish: this entry is correct to say that
24 February is the extra day but has little
to say about the Latin. Curiously it mentions
the Italian word but asserts that this is
Dear Ruben,
That is an interesting document and what you
say is strictly true but it requires thinking
backwards!!
The document says:
San Matias 24 febrero en los anos comunes,
y 25 en los bisiestos
This is right. The difficulty, as you say,
that we are in reverse mode!
Thus,
. I accept
that sundial visits to the Great Mosque
in Damascus just now are probably even
more challenging.
Tomorrow is the Calends of March and we
can all get back to normal after recent
calendrical excitements!
Frank King
Cambridge, U.K.
Dear Patrick,
Thank you for your message
at the poles.
Extending the theme somewhat, it is a little
less well known that during the 24-hour arctic
night you can have 24-hour moonshine.
Frank King
Cambridge, U.K.
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Dear Roger et al,
You are right that the BSS website is down
at the moment. This has been confirmed as
a problem with the server at the ISP and it
is not just the BSS site that is suffering.
My apologies to all who are inconvenienced.
It seems this is a challenging problem to fix.
Frank King
Dear Reinhold,
You write...
Create a wall of shame with lots
of funny comments...
Your story is full of drama. There is
good news...
...Herr Kriegler sei der beste Lehrer an
der Schule...
Then the bad news...
...da hatte dieser Satz die Wirkung eines
Stichs in ein Wespennest.
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 Transit will not
be as rewarding as that in 2004. This time
I shall be lucky to see the final stages
shortly after sunrise on Wednesday.
In 2004, several colleagues and
to allow for changes in
isostasy too, the ground will undoubtedly have
heaved or dipped over time.
Real life always asks tough questions!
Frank King
Cambridge, U.K.
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Circle a little surprising in
this special case :-)
Frank King
Cambridge, U.K.
---
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get 12 hours
on the south side in the southern hemisphere!
Alas, here it is raining so no sun at all, and in
half an hour I am leading 20 visiting academics on
a sundial walk walk:-(
Enjoy the sun if you have it!
Frank King
Cambridge, U.K
Dear Tony,
Google Images indeed represents a splendid
resource and you can find lots of good pics
of sundials and, if you wish, pictures of
noted celebrities too.
Try entering Tony Moss and you will see
that you have more impersonators than Elvis!
Still, the real thing is there around image
via a
500W lamp which I take into the classroom!
Frank King
Cambridge, U.K.
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Dear Jim,
Yes, this sounds like progress...
A more permissive gnomonic environment
may only be a few short steps away!
Indeed! We shall look back on all this as
The Dark Period of Gnomonic Prohibition!
All the best
Frank
---
Dear Jackie,
You ask...
...why it is round, not oval which one
would expect?
It's the camera angle. Try looking at
it from this direction:
http://www.flickr.com/photos/coughsplutter/7386827686/in/photostream/
If you want a round analemmatic sundial
you have to go to Naples:
Dear John,
Many congratulations. A truly amazing
project...
Owners of Tony Moss sundials are justifiably
proud of their instruments and like to show
them off. That said...
I strongly suspect that you are the first
owner to have constructed an entire railroad
for this purpose!!
More off-list.
) makes
a tangent to the ellipse. These are the
times when the direction reverses.
I wonder how many readers think that
I am kidding :-))
Life can get tough when you start thinking
about special cases!
Frank King
Cambridge, U.K.
---
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in diameter. Next
to John's Railway this would be 560 feet
in diameter. I await the subject line:
Man fails to climb 560' Sundial
Frank King
Cambridge, U.K.
---
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with other ancient Egyptian dials?
Frank King
Cambridge, UK
---
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Dear All,
Widely reported in U.K. news reports
today are the top five questions
that children ask their mothers:
1) Why is water wet?
2) Where does the sky end?
3) What are shadows made of?
4) Why is the sky blue?
5) How do fish breathe under water?
I am delighted to note that
Dear Gianni,
You give us a deligthful story.
I have a problem...
... the poles are singular points!
Yes, but these singular points do not
keep still!
...to keep always vertical without
any movement...
Unfortunately, polar wandering
means that Mr Thin would have to
keep moving to stay at
A state diagram
An argand diagram
The relationship -1 = e^(i.pi)
Frank King
Cambridge, UK
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I should, of course, have added:
Happy Birthday to Leonhard Euler
306 years old today and still going
strong!
It is a happy coincidence that he
should have been born on the day
that the Equation of Time changes
sign.
Frank King
Cambridge, UK
Dear John,
Tee hee...
The EoT might change sign on Euler's
306th birthday but I very much doubt
(without checking!) that the changeover
was the same on the date of his birth!
I did wonder about that and hoped no one
would query it!!!
According to the NOAA Solar Calculator,
the changeover
Dear Helmut,
It is good to have your confirmation that
the EoT changed sign on 15 April 1707.
John Davis made me nervous!
Of course, this wasn't 15 April here in
England, and the only outstanding worry
is that Basel was still on the Julian
Calendar. I know that different parts
of Switzerland
, now do it again and get
it right second time!
Frank King
Cambridge, U.K.
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Dear Roger,
I do enjoy your thought-provoking messages!
I have been thinking over your comments on
the globe dial:
I call sundials like this Terminator
sundials as they tell time by the
terminator line between the sunny
and dark sides.
So far, so good. An eloquent description
of how
Dear Frank,
I am fully with your assertion that...
Lime mortar is a material of importance
to diallists.
It is magic stuff but many builders today
do not appreciate it or even know how to
use it.
I have one micro-quibble with one of your
comments...
For repairs and pointing to stone dials
always
go at much the same time of
year the error should be
consistent!
That said, I think 10 seconds
is pretty good.
Frank
Frank King
Cambridge, U.K.
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of the great things about sundials
is that even the simplest problem gets
tougher once you look at it carefully!
Frank King
Cambridge, U.K.
---
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Dear Gianni,
As always, you are quite right, but there
is more to say...
In all the methods to calculate or
draw sundials, geometric or analytic,
the Sun is always considered punctiform,
and reduced to its center,
Yes to all that.
...and no account is taken of
refraction...
Yes AND
Dear All,
The BBC has got hold of an alarming
story at:
http://www.bbc.co.uk/news/uk-england-norfolk-26968617
This is clearly something designers
should pay attention to.
Frank King
Cambridge, U.K.
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