Talk:Sundial

From Wikipedia, the free encyclopedia
Jump to: navigation, search
WikiProject Time (Rated C-class)
WikiProject icon This article is within the scope of WikiProject Time, a collaborative effort to improve the coverage of Time on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
C-Class article C  This article has been rated as C-Class on the project's quality scale.
 ???  This article has not yet received a rating on the project's importance scale.
 
Wikipedia Version 1.0 Editorial Team / Vital
WikiProject icon This article has been reviewed by the Version 1.0 Editorial Team.
 
B-Class article B  This article has been rated as B-Class on the quality scale.
Taskforce icon
This article is a vital article.
edit·history·watch·refresh Stock post message.svg To-do list for Sundial:

Here are some tasks awaiting attention:
  • Expand: * Materials and construction: finding true North, stained glass, thermal expansion/invar
    • Curved styles: astroid and cycloid dials
    • Globe dials, such as Jefferson's
    • Discuss ancient types in more detail, esp. merkhet, chalice, Ahaz and antiborean
    • All forms of card dials, e.g., Capuchin dials
    • More on equatorial projection dials
    • Better discussion of altitude dials, esp. back-staff, shadow-length and ring dial
    • Devote whole section to the analemma and equation of time
    • Find good obelisk image
    • Find source(s) for Pocket Sundial; could start at Antiques Roadshow Archive, a pocket dial done at some point.
Priority 1 (top)
For more details on this topic, see Talk:Sundial/Archive 1.

content in reference section[edit]

reference number 12 is not a pointer to a reliable source - it is "content" which is better suited in the main article - i was going to mark the "content" contained in reference number 12 with a "citation needed" but don't seem able to do that - this looks like a way to insert content without any source reference - if you know how to deal with this issue - let me know Johnmahorney (talk) 19:54, 22 August 2012 (UTC)

A lot of articles have the title "References and footnotes" instead of just "References". This allows users to click on the numbers and see footnotes, where applicable, with no confusion. This article had just "references", so I've made the change. Incidentally, number 12 is not the only footnote in the list. DOwenWilliams (talk) 20:26, 22 August 2012 (UTC)

Moratorium on new upright images.[edit]

IMO the article is being swamped again with pretty but uninformative images. More so because they all have huge captions trying to explain and justify their inclusion, and many are far too tall. This is making the article unreadable, and the rendering abyssmal. Has anyone any suggestions other than some wholesale zapping. --ClemRutter (talk) 21:13, 21 April 2009 (UTC)

I've moved 8 images (which didn't need to be locked to a section) to a Gallery at the end, also floted the TOC, to allow more text at the top of the page, hope that looks a bit better  Ronhjones  (Talk) 22:14, 21 April 2009 (UTC)
Any moratorium on new images of sundials should only apply to images of northern-hemisphere sundials. The article has no image of a sundial from the southern hemisphere. This lack needs to be remedied so the article complies better with WP:NPOV. -- B.D.Mills  (T, C) 11:45, 12 February 2010 (UTC)
No. Two issues. The WP:NPOV is better handles by raising this in a new section- which I have done for you.--ClemRutter (talk) 13:33, 12 February 2010 (UTC)
After reconsideration, I agree. I'll also add to your section below.-- B.D.Mills  (T, C) 06:23, 23 February 2010 (UTC)

Lack of meaningful sundial photographs from Southern Hemisphere[edit]

The article has no image of a sundial from the southern hemisphere. This lack needs to be remedied so the article complies better with WP:NPOV. Could someone upload some images onto commons. --ClemRutter (talk) 13:33, 12 February 2010 (UTC)

Also, we need a few pictures of sundials that are located between the tropics of Cancer and Capricorn. In this region the sun can pass to the north or the south depending on the time of the year, and this places different constraints on the design of sundials as opposed to sundials in more temperate latitudes. -- B.D.Mills  (T, C) 06:27, 23 February 2010 (UTC)
There are very few sundials in the Southern Hemisphere because the rapid variation of the Equation of Time ruins their accuracy during the southern summer. DOwenWilliams (talk) 05:30, 6 December 2011 (UTC)

Mass dial / Scratch dial[edit]

BBC News article of 21 August 2009 discusses recent discovery of a Mass dial in Scotland - http://news.bbc.co.uk/2/hi/uk_news/scotland/edinburgh_and_east/8214948.stm .
6,000+ Google hits for "mass dial" - http://www.google.com/search?q=%22mass+dial%22 .
Apparently these are also called "Scratch dial".
Our article apparently doesn't mention either of these terms. We should add a mention of these, and make Mass dial and Scratch dial redirect here. -- 201.37.230.43 (talk) 13:17, 22 August 2009 (UTC)


Future of this article as it is presented (March 2010)[edit]

Hello everybody!

The subject of “Sundials” is a complex one, even for those who have more than a passing acquaintance with it. I'm not put off by complex things, but I know that they don't necessarily have to be difficult to understand. The simplicity comes from the way they are presented.

The comment at the head of the article page (May 2009) and several on this page are concerned with the article's presentation and its evolving unwieldiness. It's been some time since there was any activity to improve it overall, and the situation is worse. It's still too long to read and navigate comfortably. The same thing could be said for this Talk page.

If you're put off by it, forgive my preaching to the choir ... ... ...

I believe this article must fulfil two objectives:

  • To inform readers who wish to acquire knowledge about Sundials
  • To provide encouragement for those who wish to explore the subject in greater depth.

I don't believe that the article, in its present form, achieves either of these things. But not only because it is long.

It must be presented in the most appropriate way for its audience. That's the most important element of its design and can be achieved without compromising purpose. There are two different types of people who read this article:

  • Those who lack a prior knowledge and who want to gain a rudimentary grasp about a complex subject.
  • Those who have a grasp of the subject and want a fuller comprehension of different types of sundials, their history, construction and so on.

The article tries to be encyclopedic about the entire subject, but there’s no evidence that attention has been paid to the approach of either type of reader.

  • The article doesn't provide a good overview for novices. For example:
There are no diagrams (as distinct from photographs) showing the different parts of a sundial or the different types of dial.
There's no easy-to-read glossary. The Terminology section isn't one.
  • The article doesn't provide easy and appropriate access to the deeper elements of the subject.
The Contents frame is too long to read at one glance.
Different terms are explained repeatedly throughout (e.g. gnomon) or are explained when they arise in the article instead of in a Glossary.
Some of the simpler concepts (e.g. Human Shadow, Shepherds Dials) are described after more complex ones (e.g. formulae for different types of reclining dials).

There are other things that don't help:

Some of the images in the gallery would be more useful if they were relocated adjacent to the appropriate section.
Although there's a To-Do list, any work on them wouldn't necessarily make the article any less complex. An increase in content will most likely make it more complex. The same thing would happen if other articles were redirected here.

This Talk page is no different in its unwieldiness. There have been (and still are?) tangential issues that have arisen and only serve to further obfuscate the work of editors in maintaining and improving the article. There's a huge morass to wade through for anybody who wasn't/isn't directly involved. Likewise, it could be easier to keep track of the changes here. Rather than letting its complexity dictate to editors, editors should be able to keep it simple.

I also don't believe that any other existing articles should be redirected to this one unless they are duplicates.

I agree that this would be resolved if the article was divided into several, each dealing with a discrete element of the entire subject of Sundials. In that, it would be no different than, say, an article about Europe which links to separate articles about France, Germany, Italy, etc.

To make any changes, though, in a subject that has already proven to be emotive, there has to be a consensus - at least one of intent.

If there is a general agreement that separation is the way to go, I suggest that it’s not a job for one person, but for a group of individuals to agree how it should be separated and to write discrete articles, each one linked back&forth, of course, to a main (summary?) Sundial article.

Thoughts, anyone? Twistlethrop (talk) 09:07, 8 March 2010 (UTC)

Yes yes and no. Yes it is time to do a major re-edit. Since the last major edit I did, the article has become even more bloated- a wheelie bin for every fact relating to a sundial, noon mark and if we let them- garden gnomes. I am short of time at the moment and away from my reference books. So brief blunt commonts
  • Photographs are a hazard- too many illustrate little- the pretty ones have been left in the gallery- they need to be culled not inserted.
  • Aims of the article. I mainly agree but must add that a dial is primarily a mathmetic instrument and the geometry is paramount. If left unmonitored it becom es a collection of holiday snaps.
  • Terminology- is inconsistent in the sundial world- take style/gnomon. Yes cull the repetitions but check that the inline def for that pargraph isn't at odds with the meaning in the previous paragraph.
  • Yank out a whole section about pre-reformation time keeping methods- I was about to do this- just couldn't think what the new article should be called.
  • Sundials in France article- anyone is free to do it- but it won't help here. This article is not a tourist guide for looking at the pretty pretty. An article on the Art on vertical declining dial plates would be cool.
  • Articles on construction of dials that is for wikibooks.
  • We are not the first ones to have hit these problems- look at the reference books- then examine the changes between the second and third edition of Mayall and Mayall.
  • You are wrong on simplicity when it comes to shepherds dials- they look simple but mathematically you need the preceding concepts to understand them- the projection is hideously complex. They also are rare compared with preceding vertical decliner or garden dial. Fine, there are other ways to order the article.
  • SVGs explaining the geometry. Yes. Using existing ones, no- they must be mathematically correct- most aren't. Doing a derivative from Waugh or Mayall- even there the maths needs to be checked.
When I did the last major edit, I built up the article in my sandbox. I like your ideas, but can I suggest the next stage is that you draft a proposal in your sandbox, and then invite comment. This is a well policed article- but the number of content providers has been limited. You do need to put in a sizeable of editing before there is a finished package ready to go live.--ClemRutter (talk) 10:17, 8 March 2010 (UTC)
I have split the article today, spinning off History of Sundials. Even so, I have only lost 9000 bytes. I will do a ce and see if I can tx any more soon. --ClemRutter (talk) 22:55, 8 May 2010 (UTC)

Sun dial coaching center[edit]

There is a coaching center established in 1985 in Rajshahi, Bangladesh, called Sun Dial. Which is the best coaching center for higher level education in the whole town. —Preceding unsigned comment added by 180.234.30.194 (talk) 18:19, 1 September 2010 (UTC)

Pocket sundials[edit]

There's a image (currently unlnked) of a pocket sundial at http://en.wikipedia.org/wiki/File:Sundial_pocket_watch.JPG Might be worth adding to that section...

214.4.238.180 (talk) 21:14, 23 September 2010 (UTC)

Shadow clock[edit]

Shadow clock redirects here, but nowhere can an explanation of what they are (sp. as compared to a "regular" sundial) can be found... CielProfond (talk) 03:16, 2 November 2010 (UTC)

Questionable reference in "Sundials in the Southern Hemisphere"[edit]

I question the accuracy of this statement:

"Sundials are not as common in the Southern hemisphere as in the North. This is possibly because when Europeans arrived the mechanical clock was accurate enough for their purposes of time keeping and there was no need to erect sundials.[8]"

It points to "History of the Sundial" by Helga Nordhoff. The linked page is titled "Sundials in South Africa", and never extends the perceived (and somwhat questionable) lack of sundials in South Africa to the whole Southern Hemisphere. I think we can't possibly limit our information on the Southern Hemisphere to what goes on only in South Africa, am I right?

Also, both the freely-edited version as it is and the linked text fail to acknowledge the Southern Hemisphere's history before European arrival. Ancient civilizations are known for their vast knowledge of astronomy, so although I don't have any reference to base it, I'm pretty sure the use of sundials wasn't an exclusively-European phenomenon.

The linked text goes as far as to say:

"The general public in South Africa is very ignorant about the role sundials played in the history of time keeping and only a few people actually know how a sundial works.

One can easily notice how POV this sounds, and I have serious doubts about using any text from this source on this article. I'm not a frequent editor, so I'm choosing not to edit anything right now. Also, I don't know how can we verify if a source has Notoriety status or not, but I'd encourage fellow editors, possibly more experienced than I am, to look further on this reference number 8, Helga Nordhoff's History of the Sundial. Ebacci EN (talk) 10:55, 22 February 2011 (UTC)

I totally agree the original reference was linked to the information in the text, I will try to go back and find it. In terms of the rest be bold, if you do not I am happy to. Thanks for pointing this out I missed the original edit.Edmund Patrickconfer 20:35, 22 February 2011 (UTC)
On the point about southern hemispheres and sundials what is referenced is the lack of public time telling sundials as if "brought" over from the northern hemisphere. Most excellent books can reference indian, chinese, mesoamerican etc time measurements as well as iniut, but no imperical records have yet been found, researched and published on time keeping from Southern Hemisphere, which would be absolutely wonderful to see how they measured time, as we now do, and even if it was it linear! Edmund Patrickconfer 21:22, 22 February 2011 (UTC)
I concur.--ClemRutter (talk) 23:00, 22 February 2011 (UTC)

Sundials are usually used in summertime, bee sun generally shines more. During the southern summer, a sundial is a hopeless timepiece, compared with a clock, because the Equation of Time changes fast. During the northern summer, it changes much less, and can be ignored without much error. Therefore, for simple physical reasons, sundials are better suited for use in the Northern Hemisphere than the Southern.

Not only in South Africa are most people ignorant of sundials. In Chile, almost nobody has heard of them. I constructed one in Santiago a few years ago, which caused something of a sensation. It was photographed for the press. Of course, it was just a toy. Nobody tested its accuracy.

DOwenWilliams (talk) 05:25, 6 December 2011 (UTC)

This statement about the equation of time is nonsense. It is exactly the same on the Southern Hemisphere. Please read the article on the Equation of Time: there is nothing specific for the Northern Hemisphere. I removed the wrong paragraph.Csab (talk) 16:14, 27 July 2012 (UTC)

I put it back, since it is NOT wrong. The Equation of Time changes rapidly between November and February, This is true everywhere on the Earth. But in the Southern Hemisphere, it is summertime, and in the Northern Hemisphere it is winter. Between May and August, during the northern summer and southern winter, the Equation of Time changes far less. Since sundials are used mainly in summer, they are affected much more by the varying Equation of Time in the southern hemisphere than the northern.
Please look at the graph of the Equation of Time, accompanying the relavant text in this article. Also, re-read the Equation of Time article. (I wrote a lot of it.)
DOwenWilliams (talk) 22:01, 27 July 2012 (UTC)

Questionable statement in "Globe Dial" under "Unusual Sundials"[edit]

I question the statement that this style of sundial was popularized by Thomas Jefferson at Monticello.

It does not cite any sources to back the statement, and there's nothing about it either on Thomas Jefferson or Monticello.

I reckon this can be some sort of urban legend, but if so it should said so. Ebacci EN (talk) 11:19, 22 February 2011 (UTC)

Agree.--ClemRutter (talk) 23:01, 22 February 2011 (UTC)

Being bold[edit]

I see you have re-linked the reference to the book "The Story of Time", but I failed to find any source to reiterate that statement. I'll try to find the book but if you have a link, it would be much appreciated. It's not that I disagree with the "less common" statement, which I believe to be probably true. But on a quick search I could find evidence of pre-European sundials, and not just a few, in Ecuador, Mauritius and New Zealand - all oriented towards the South.

Also, the Thomas Jefferson reference remains without a source.

Acting as by your suggestions, I'm being bold and removing both controversial statements. I'll look for good sources in libraries that might corroborate or disprove such statements, but as it is now I believe some myths or misconceptions are being perpetuated (as I've seen many websites referencing this article, including the controversial statements).

I apologise if my actions were not taken in the correct manner. I'm more than willing to learn from my mistakes if you're kind enough to point them out for me. Ebacci EN (talk) 00:06, 28 August 2011 (UTC)

Analemmatic sundials[edit]

Please forgive this newbie (both to Wiki and the Sundial article) question. In section 7.2 the last sentence of the section states in part "... object's shadow to measure time, not only the hours, as in normal sundials, but also weeks and months." (emphasis added). How exactly does the shadow of the gnomon measure "weeks and months"? Jcflnj (talk) 13:01, 1 September 2011 (UTC)

Hours of sunlight[edit]

This is to Tyger27, who edited the article today. He said this:

"Unlike horizontal dials, a vertical dial cannot ever receive more than twelve hours of sunlight a day, no matter how many hours of daylight there are."

Actually, that's not true. In the northern tropics, a north-facing vertical dial receives sunlight from sunrise to sunset. Near the summer solstice, this can be substantially more than 12 hours per day. The same is true for a south-facing dial in the southern tropics.

I have Waugh's book, which you cited frequently. I don't see anywhere where he says that a vertical dial cannot receive more than 12 hours of sunlight per day.

DOwenWilliams (talk) 20:34, 13 June 2013 (UTC)

Unreferenced digital sundial[edit]

===Digital sundial===

Digital sundial: lifelike drawing showing clearly the cracks through which the light shines so that reading the time in digital figures is possible
Main article: Digital sundial
A digital sundial uses light and shadow to 'write' the time in numerals rather than marking time with position. One such design uses two parallel masks to screen sunlight into patterns appropriate for the time of day.[citation needed]

I have been alerted to this section by :nl:User:Willy Leenders uncommenting a portrait format graphic. It is unclear to me from the text whether these things exist or not. There is no citation. If they exist I want one! Even if they do exist I think the graphic needs to be cropped so it is in landscape format, and we need a clear explanation of what we are seeing. Following the link brings us to an article seems to contain a lot of unrelated maths. Any references, any thoughts. -- Clem Rutter (talk) 19:44, 10 July 2013 (UTC)

I think they may exist. Whether they do exist is a different question. One of the designs described in the text involves a narrow slit, through which sunlight passes, illuminating the ends of some optical fibres. As the sun moves across the sky, different fibres are illuminated. The fibres lead to a display of digits. For example, if the second minute digit is a 3, so the time is 1:13, 5:43, or whatever, the fibres that are illuminated lead to a digit 3. The other digits are treated similarly. So the display shows the time in digital format. Apparently, there is another design with two screens that somehow produce the same result. I haven't tried to understand it yet. DOwenWilliams (talk) 21:54, 13 July 2013 (UTC)
Ah! I see how the two-screens thing works. It's the one shown in the image. It works when back-lit, so the Sun is behind the display, as seen by the viewer. One screen is perforated with parallel slits. (You can see them by magnifying the image.) The other is similarly perforated, but the slits are shorter, showing the shapes of the digits. Light can pass through both screens only when the angles are right so the appropriate digit appears.
But I'm sceptical. The Sun takes about 2 minutes to cross its own diameter as it moves in the sky. This kind of display couldn't show the time to the exact minute. The digits would be blurred. So I'm inclined to suspect that this whole thing is a fantasy.
DOwenWilliams (talk) 22:23, 13 July 2013 (UTC)
I can almost swallow the description for the hours digit- but like you say it would take a two minutes transition from 3pm to 4pm- but there would need to twelve precision masks focusing on each pixel- but I cannot see how the minutes would work- for the tens, there would need to be a 6x12 masks and the units 10x6x12 masks all not interfering with each other. That and the need to vary each of them to compensate for the annual variation in the elevation of the sun. If we are talking about such finely draw grids- we have in effect set up a diffraction grating. I look forward to seeing one or to read the PhD thesis. -- Clem Rutter (talk) 23:09, 13 July 2013 (UTC)b
I don't pretent to follow the technicalities, but for the record I don't think anyone is claiming these things would be accurate to the minute, but rather to the nearest 5 minutes: see this patent (linked from the Digital sundial article), which talks about "a minute display showing, for example, the 12 five-minute intervals". GrindtXX (talk) 23:54, 13 July 2013 (UTC)
I've written patent specifications. They have to sound plausible, but they don't have to be truly realistic. I am increasingly convinced that nobody has made a functioning digital sundial that works by simple optics. Conceivably an electronic device that accurately senses the position of the sun in the sky then drives something like a LED display might be practical, and functional. But would it qualify as a sundial? No. Unless and until I see a real device, or at least a photograph of one, I'm going to remain sceptical. DOwenWilliams (talk) 01:41, 14 July 2013 (UTC)
Digital sundial: the sequence of pictures explains the working of de digitalsundial

The digital sundial exist!

See one model at the sundial garden of the Deutsches Museum in Munchen (Germany) http://www.deutsches-museum.de/en/exhibitions/natural-sciences/astronomy/astro-clocks/the-sundial-garden/

See another model in the Sundial Park in Genk (Belgium) nr. 8 at http://www.fransmaes.nl/genk/welcome-e.htm

The figure attached explains the wordking.

Please place the article back.

nl:User:Willy Leenders 17:35, 4 august 2013 (UTC)

I was in München up until 31st July- I could have gone and taken a better photo. And it was sunny! With the new material, I can go and add to the section- and improve it. Starting with a line that says that: -- the quest for a digital sundial started with a article in the Scientific American....-- Clem Rutter (talk) 08:43, 24 September 2013 (UTC).

inexpensive decorative sundials may have incorrect hour angles[edit]

Inexpensive sundials may well be inaccurate, but the reference to this is based on a single comment some 40 years ago. Since then, most of the manufacturers of sundials have long gone, replaced by others. Which may - or may not - be as accurate or as inaccurate. The reference was weak 40 years ago; it has zero bearing on the present, and should not be there. I have removed it, and my edit has been vandalized twice. Please DO NOT reverse my edit; but feel free to replace it with a new source if you have one. Thanks. Heenan73 (talk) 00:50, 21 September 2013 (UTC)

There's a difference between vandalism and reversion. Your edit was reverted twice, once by myself and once by someone else, because we considered your reasoning to be inadequate.
Professor Albert E. Waugh, of the University of Connecticut, was an expert on sundials. A brief quotation from his book on the subject carries more weight than a hundred quotations of other people. I have owned a copy of the book since soon after its publication. Whenever I want to know anything about sundials, I consult it.
Relatively recently, maybe ten years ago, my wife gave me a sundial as a birthday gift. It was, and still is, a decorative object, but I soon disovered that it is useless as a timepiece. The hour lines are spaced evenly around the dial, which is completely wrong for a real sundial, except one designed for use at one of the Earth's poles. I live closer to the Equator than the Pole. Here, this dial is useless. I wish my wife had read Waugh's book before buying this dial. She'd have saved some money, and maybe bought me something better.
The one-line warning, which User:Heenan73 insists on removing from Wikipedia, may prevent someone from making the same mistake as my wife did. It should not be deleted.
Incidentally, the warning was in the article for a long time without any citation to back it up. At some point, some editor with a liking for graffiti daubed "citation needed" on it, and it stayed in that form for a long while. Fairly recently, someone took the bait and added the citation of Waugh's book. Then Heenan73 decided this wasn't to his taste, and deleted the whole thing, including the warning. I think the warning should be replaced, with or without the citation.
DOwenWilliams (talk) 02:21, 21 September 2013 (UTC)
vandalism: do not call a person who edits once a vandal I asked a perfectly reasonable question and this is the reply. I buy a none functioning garden centre sundial at least once every two years for my introduction to sundials workshops for adults / young people and families to show them they they need to exercise care when purchasing one. The last one I bought near Cambridge has a angle of 38 something degrees as accurately as we could measure the lump of concrete. I am going to replace the line and later look for more references. Shame i cannot reference myself! Edmund Patrickconfer 08:23, 21 September 2013 (UTC)
A second reversion, even by a second person, of a perfectly valid edit, is vandalism - especially when zeroattempt is made to justify the act beyond the illogical claim that "not quite sure why not reliable here but is elsewhere." - I have no problem with the author or his work; my interest s in how it is used in Wikipedia. In this particular case, it is inappropriate. So I removed it. If you are concerned about peoples' shopping experience, there are other, better, ways to deal with this, than placing unsubstantiated words in wikipedia, made the look 'kosher' by an inappropritae reference. Heenan73 (talk) 10:46, 21 September 2013 (UTC)
but you see, out of the three editors trying to discuss this you are the only one that has the opinion ...of a perfectly valid edit. ...the illogical claim that not quite sure why not reliable here but is elsewhere... is based on the nineteen (19) other references from Waugh used in this article alone. Here is a man who produced a respected book on Sundials which is worthy of reference throughout the article and is recommended for further reading, but for some reason the fact that he states that some bought or commercially made sundials will not be accurate is not acceptable I found confusing, so I reinstated whilst asking what changes were needed. The language definitely needs a tweek and hopefully we are heading towards a common ground. Edmund Patrickconfer 13:16, 21 September 2013 (UTC)
Thank you, DOwenWilliams and Edmund for looking after this page while I have been on vacation (six km from public internet). I wrote the text, sourced from Waugh and Mayell and Mayell p53. Years later when references became more important I filled in the detail. I will restore the text as it is still valid and if Mr Heenan wishes to change the text it, He no doubt will just quote the a reference to a text that reads 'Since 1973, inaccurate cheap sundials have removed from the market in all parts of the world making Prof. Waughs concerns invalid.' However I think not. There is still a lively market for decorative brass dials, and painted ceramic dials in the street markets in Provence. The document Illustrating Shadows What not to buy written in 2007, but I preferred to use Prof. Waugh the known authority, The illustrating shadows pdf is CC-BY so could be transcluded; the author is stated to be a member of both the BSS (British Sundial Society) and the American one but they are not named. Perhaps Mr Heenen would prefer it -if both were included, and we could pen some information on the prevalent problems but I would prefer to spin this of into a separate article.-- Clem Rutter (talk) 19:15, 21 September 2013 (UTC)

For the third (4th?) time, I have no quarrel with Waugh or his work; I have little quarrel with the statement made. My problem is matching the two. While clearly a leading expert in the field, Waugh's comment on quality was a throwaway line in his book - effectively, no more than an opinion - and it is not appropriate to use that for a reference. It demeans wikipedia, and it also demeand Waugh's work. I see now that two other references have been added - fine by me, they are both pretty poor sources - but the reader can see that instantly, whereas the Waugh reference suggests a degree of rigor that does not exist. Instead of defending a poor reference, why not go out there and do some research; a fine article like this deserves better than citing one example of a bad sundial, generalized to dismiss all cheap sundials in the world, with no evidence. For all I know, the new generation of Chinese-made models may be perfectly engineered - unlikely in the extreme, but this article does not (reliably) tell me, does it? Editors should avoid the temptation to feel their work is perfect and set in stone; that defeats the whole purpose of wikipedia as a living resource. Heenan73 (talk) 09:27, 22 September 2013 (UTC)

To work well, a sundial must be made specifically for the latitude at which it will be used. Mass-produced dials that are sold in stores scattered over a substantial range of latitudes inevitably work poorly.
I do agree with your last sentence. DOwenWilliams (talk) 14:57, 22 September 2013 (UTC)
@Heenan, I admire your tenacity but you have missed the point. Can you think of any more suscinct way of expressing the fact, that dialists have been concerned about 'Mass-produced dials' we have references from Waugh, Mayall and Mayell and from 2007 from the BSS and ASS. The references and the sentiment stands- my prose is awful and can be improved. If we were into OR we could possible prove that it was the problem caused by Mass produced dials that Inspired Mayall and Mayall to write the Scientific American articles on which their book was based. No matter- can you advise on any corrections that are needed to the rest of the text to take this article to GA or FA. -- Clem Rutter (talk) 16:03, 22 September 2013 (UTC)
With respect, I haven't missed the point at all; but I suspect you have. The point is NOT sundials - the point is Wikipedia. I really, really, really am not arguing the point about sundial quality (how many times must I say this?) I am arguing about how you write and maintain a wikipedia page. Sundialists may well be concerned about quality (I'd hope so!!), but for a quality encyclopedia, that alone does not justify taking opinions (however widely shared) and stating them as referenced fact. Indeed, it is a little sad that with sundialists being aware of the problem for 40 years, no-one HAS written a quality article on the subject. Waugh's concern is a matter of record; what (apparently) is NOT a matter of record is whether he was right or not (though I am sure he was). It doesn't take tenacity, it just takes common sense; I am NOT a sundial expert (though I know a little). But I do know about references. And THAT really is the issue here. Don't fall into the wikipedia editors' ownership syndrome, where you assume not only superior knowledge, but ownership of the pages - that way the ruination of wikipedia lies. Heenan73 (talk) 15:39, 23 September 2013 (UTC)

Take a look at my User page, especially at the second story about citations. In reality, there is no such thing as an absolutely reliable reference. People make mistsakes. Opinions change. Theories become outdated, and so on. Factual accuracy is the main consideration. Whether anyone has written an account that satisfies Wikipedia's criteria for citeability is secondary. Always. DOwenWilliams (talk) 21:05, 23 September 2013 (UTC)

@Heenan, Fine-- just air your concerns on the talk page first- and you would find you are actually swimming in the same pond.-- Clem Rutter (talk) 08:35, 24 September 2013 (UTC)

Edit request[edit]

in the lede we learn that the "style" is the shadow creating edge of the gnomon and must be parallel to the Earth's axis. In the Introduction ( in its 2nd paragraph as of 9/21/2013) we learn the the gnomon is "aligned with the Earth's axis, or oriented in an altogether different direction determined by mathematics." This seems to be contradictory. Please fix.173.189.74.6 (talk) 18:08, 21 September 2013 (UTC)

OR flag in Southern Hemisphere section[edit]

There are a number of other reasons why one find fewer sundials in the Southern Hemisphere.

  • There are fewer people in the Southern Hemisphere.
  • The indigenous peoples of the Southern Hemisphere did not measure time to any degree of accuracy. By the time that the Southern Hemisphere was colonized, clocks and watches were in common use, making sundials redundant.
  • Construction of a sundial based on a flat plate is difficult in the tropics - the sun moves between the northern and southern skies with the season.

In view of this, I would suggest removing the paragraph that I have flagged as OR (unless a RS can be found). Martinvl (talk) 04:29, 14 October 2013 (UTC)

Clocks needed to be reset quite frequently, and sundials were the only available means for doing this. Also, there is no Pole Star in the Southern Hemisphere, which would make it more difficult to set up a sundial with its gnomon pointing to the South Celestial Pole. DOwenWilliams (talk) 04:37, 15 October 2013 (UTC)
There is a "rule of thumb" (literally) for finding south using the Southern Cross - see Crux#Use in navigation. (I have added this section in the last hour using a book on my bookshelf as a reference). When living in South Africa, I used this technique many times.
Mariners have developed techniques of finding midday with a good degree of accuracy without the use of sundials. These techniques were well known before there was any meaningful European settlement in the Southern Hemisphere. By the time such settlement had taken place, books of tables giving the equation of time were well established and were used in both the Northern and Southern Hemispheres.
I regard your argument as a red herring and stand by my original argument that there are fewer people in the Southern hemisphere - the major centres of population south of the Tropic of Capricorn being South Africa, (most of) Australia, New Zealand, Argentina, Paraguay, Uruguay, half of Peru and the south-western corner of Brazil - fewer than 200 million people. In contrast, the land north of the Tropic of Cancer is home to more than 10 time that number of people.
Martinvl (talk) 06:21, 15 October 2013 (UTC)

I don't dispute that there are a lot more people in the Northern Hemisphere than the Southern, one reason, of course, being that there's a lot more land in the North. But I don't see how this explains why the people who are in the South only rarely use sundials.

There's a big, fairly new, sundial in Buenos Aires, Argentina, which was made by a man who hads migrated from Spain. He said he had made it partly to remind himself of home, where, he said, there's a sundial on every street corner. Also, he wanted to show Argentinians what sundials look like, since there were very few of them in the country. (I did much the same, years ago, in Santiago, Chile. Sundials are so unknown there that there isn't a word for them in the Chilean dictionaries I looked at.)

Yes. It's possible to use the Southern Cross and other constellations to locate the South Celestial Pole in the sky. But it isn't as easy as just spotting the Pole Star.

DOwenWilliams (talk) 14:47, 15 October 2013 (UTC)

So far we have established that there are many reasons why there are fewer sundials in the Southern Hemisphere compared to the Northern Hemisphere. To single out just one, as happened in the article, is therefore incorrect. Moreover, the assumption that sundials are more use in summer than in winter is a gross assumption. In Johannesburg (where I lived for about seven years), a sundial would be more useful in winter than in summer because there is virtually no cloud cover in winter. (Cape Town is of course totally different). Martinvl (talk) 15:58, 15 October 2013 (UTC)
In the article, it says that "one reason" for sundials being little used in the Southern Hemisphere is the asymmetry of the Equation of Time. It does not say, or imply, that this is the only reason. In fact, it implies the opposite.
I would suggest that Johannesburg is unusual in having more sunshine in winter than summer. There are other places with the same trait, Costa Rica, for example, but they are rare. Generally, summer is a better time for sundials than winter.
DOwenWilliams (talk) 19:16, 15 October 2013 (UTC)


Reclining-declining dials[edit]

Awaiting input from ip-user.-- Clem Rutter (talk) 19:37, 29 November 2013 (UTC)

Warning: a lot of good faith recent input is with out references - and reads like a undergrad maths essay and so is un-intellible to the general reader- this week end I will be culling unreferenced materials and standardising the symbols on those defined by the British Sundial Society Glossary also found in the North American Sundial Society repository. Unreferenced interesting maths will be trasfered here for discussion.-- Clem Rutter (talk) 10:23, 28 March 2014 (UTC)

Universal equinoctial dial & Holbein's *The Ambassadors*[edit]

I just was looking at the Ambassador's article and its discussion of various timekeeping instruments, which brought me to this article.

It says here that it was invented in 1600, however, according to the Ambassadors discussion it would have had to have been invented by 1533 for it to be included in that painting.

I don't know how to resolve this kind of discrepancy according to wikipedian common practice, since both claims seem to be cited, but they definitely seem to be mutually incompatible.

Mdpacer (talk) 21:50, 7 July 2014 (UTC)

« Cadran bifilaire », Why ?[edit]

I don't know why this article is pointing on fr:Cadran bifilaire instead of fr:Cadran solaire. The Wikidata element is correct and the German Wikipedia gives the good element. Simon Villeneuve (talk) 13:31, 23 December 2014 (UTC)