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Latest comment: 12 years ago2 comments2 people in discussion
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)Reply
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)Reply
Latest comment: 14 years ago5 comments3 people in discussion
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)Reply
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)Reply
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)Reply
Latest comment: 12 years ago3 comments3 people in discussion
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)Reply
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)Reply
Latest comment: 14 years ago3 comments2 people in discussion
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.
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)Reply
Latest comment: 14 years ago1 comment1 person in discussion
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)Reply
Latest comment: 9 years ago8 comments6 people in discussion
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)Reply
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 Patrick – confer20:35, 22 February 2011 (UTC)Reply
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 Patrick – confer21:22, 22 February 2011 (UTC)Reply
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.
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)Reply
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.)
DOwen said that sundials are little used in the winter. No, sundials are used all year. Winter isn't always cloudy. In many regions, summer is cloudier than winter--where I reside, in Florida, for example.
The other suggestion, that European timekeeping arrived in the Southern Hemisphere after clocks and watches were well-established in use, probably has more merit.
Latest comment: 13 years ago1 comment1 person in discussion
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)Reply
Latest comment: 6 years ago2 comments2 people in discussion
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)Reply
Latest comment: 11 years ago1 comment1 person in discussion
Tyger27 had said:
"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."
Someone replied:
"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."
Yes, at the summer solstice, just barely south of the Tropic of Cancer, a north wall can get almost 13.6 hours of sunlight.
(your text resumes)
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.
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)Reply
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)Reply
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.
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)bReply
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)Reply
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)Reply
Digital sundial: the sequence of pictures explains the working of de digitalsundial
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).Reply
inexpensive decorative sundials may have incorrect hour angles
Latest comment: 9 years ago13 comments5 people in discussion
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)Reply
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.
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 Patrick – confer08:23, 21 September 2013 (UTC)Reply
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)Reply
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 Patrick – confer13:16, 21 September 2013 (UTC)Reply
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)Reply
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)Reply
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.
@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)Reply
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)Reply
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)Reply
I, too, wasn't sure if Waugh's and Mayall & Mayall's warning was still relevant in modern times. So I bought some inexpensive sundials on the Internet, hoping that one of them might be accurate. No such luck.
Waugh's and Mayall & Mayall's warnings about poor quality remain fully valid today. None of the sundials that I bought on the Internet had 5-minute accuracy--very substandard for stationary-mounted sundials.
It was astonishing. In the horizontal sundials, the hour-lines were never right for any latitude, including the one that corresponded to the gnomon's angle.
The armillary sundials did a little better, but the construction expense and difficulty is greater. None of the armillary sundials I boubht had 5-minute accuracy either. Though the marking of the hour-lines wasn't the problem, the equator-ring was out-of-round, or the gnomon wasn't centered in it, or wasn't perpendicular to it.
Don't get me wrong: Inexpensive Internet-purchased armillaries are great decorations. Unless you're into weldin, that might be the best that you can do, for an armillary. But they're not accurate sundials. I couldn't find any accurate inexpensive Internet sundials.
Someone wanted academic citations to verify the uniform low quality of mass-produced sundials :^) No, that isn't the sort of thing that academics will write about in journals. But Waugh, and Mayall & Mayall were widely-accepted authorities, and their inaccuracy-warning continues to be confirmed by purchasing-experience today. — Preceding unsigned comment added by 65.8.169.50 (talk) 13:25, 25 January 2015 (UTC)Reply
Latest comment: 11 years ago1 comment1 person in discussion
Someone wrote:
"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)"Reply
Yes, that statement in the article is inaccurate, and should be deleted. Some sundials use a gnomon parallel to the Earth's axis, but some use the shadow of a style-tip, or "nodus", in which case the style's orientation isn't important. And, the analematic and Lambert sundials use the shadow of a gnomon that must be either vertical, or at some other specified angle different from the Earth's axis.
Latest comment: 11 years ago6 comments2 people in discussion
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.
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)Reply
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.
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.
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)Reply
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.
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)Reply
Can I add something here? I know that we're not supposed to edit the talk-page, but I'd like to say more on this topic, the Reclining-Declining section.
As Clem pointed out, that section, and its formulas in particular, are unintelligible to the general reader, and are without reference or support.
But there's more: The section makes some very bold claims:
"In fact it is only in the last decade that agreement has been found on the correct hour angle formula for this type of dial. ... Previous formulae given by Rohr and Mayall are not correct."
In that paragraph, the section is saying that all reclinging-declining dials made before the last decade were made wrong, and that the right way to construct a reclining-declining dial was unknown until the last decade.
Wikipedia has a policy against unsupported presentaton of new theories, and surprising new unsupported claims.
With a problem such as the reclining-declining dial, there are various different ways to solve the problem. Different solutions often result in different but equivalent forumlas. Especially, different choice and definition of the variables results in different but equivalent formulas.
Therefore, when a new formula looks different from an earlier more traditional one, that doesn't mean that the earlier one is wrong.
But, more broadly, as Clem pointed out, formulas such as that section's reclining-declining formulas are unintelligible to the general reader, and therefore aren't helpful in the article.
In fact, those formulas are a construction-instruction. Some say that an encylcopedia shouldn't have any construction-instruction. I don't really agree with that, but a construction-instruction whose justification and motivation are far from obvious (as is the case for those formulas) isn't really helpful to the reader. ...doesn't confer any understanding of the problem. ...amounts to a cookbook-recipe whose justification is unknown to the reader.
We're encoursged to be bold and make, on our own, the changes that we propose. But I'm not going to delete or modify the passages that I refer to here. I only want to make these comments.
Latest comment: 10 years ago1 comment1 person in discussion
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.
That Bifilar-Sundials section of the wikipedia Sundial article, if it links to something, should link to something that is specificlly about bifilar sundials. "Cadran Solaire" just means "sundial". It makes sense for the Bifilar section to link to a reference about bifilar sundials--the Cadran Bifilair article.
The two bifilar references in the article were to an article in French, and an artice in German. You might want to consider, instead, for each article, linking to the url at which the articles are translated into English. How do you fnd it? Search google for "Cadran Bifilaire". The line for it in Google will have a click-place that says "Translate this to English". Click on that. Then copy the url from the address-window at the upper left of your screen. I'd do it, except that I'm not going to make a modification just so that it can be deleted.
For that reason, I won't make any more modifications to this article.
By the way, that automated translation of the French article is a lot more error-free than is the automated translation of the German article. Evidently the automated translation software does better at translating French into English, than it does at translaing German into English.
The wikipedia sundial's Bifilar Sundials section is seriously, preposterously, lacking. It doesn't explicitly say that one wire (or string) is higher than the other, or for what purpose. It doesn't say what the Bifilar sundial is supposed to accomplish. It doesn't say what is the purpose of the Bifliar sundial. I added that information: The intersection of the 2 wires' shadows moves around a certain point on the dial, at a uniform rate of 15 degrees per hour...as if it were an equatorial dial. In other words, it combines the unform rate, and consequent easy interpolation, of an equatorial dial, with the easy building and all-directions readability of a horizontal sundial.
I added all that information to the article. ...plus a few words about obvious disadvantage of the Bifilar dial.
Everything that I added about the Bifilar was deleted. ...because there were no citations? Look, that information about the uniform rate is given in the French article. I so stated, in added explanation. If you don't believe that, then view the English translation of the French article (View it by the method that I described above). I merely added, to the article, some basic necessary information that is in the French reference. That information belongs in the article--Without it, the reader would have no idea of what the Bifilar's purpose is.
Such basic, relevant information belongs in the article, not just at a linked-to reference. Anyway, as the article is now, anyone who doesn't read French or German will have no way of finding out what the bifilar sundial is, and for what purpose it's made as it is.
If I'm writing additions to the article only to have them delted, than there's no reason why I should do so.
Didn't see your comment before I started todays odyssey- if you would like to go back to Bifilar sundial you will see I have taken across the fr:text and anglified it. French likes lots of maths- English gets twitchy. I have taken out some of your comments as they seem trivial now and they weren't backed by a reference.
[/quote]
You took out my statement of the Bifilar's advantage. Most people are interested in relative advantages and disadvantages. That isn't trivial. Without the advantages and disadvantages being stated, we're offering an unexplained bare menu.
The Bifilar has the advantage of combining the Equatorial's uniform shadow-motion, and consequent ease of interpoltion, with the Horizontal Dial's ease of building, and all-directions readability.
[quote]
The German source is good fun to read- I would like to see his 1914 Leipzig work- it could be a useful article for referencing this page. I need you to check the Maths, and correct any silly mistakes- particularly I would like you to sort out the reference to the meridian-did they mean the meridian plane? Does the meridian article need changing too?
.
[endquote]
.
Regarding the meridian, yes they must have meant the meridian-plane. They meant that string F1 lines on the meridian plane.
But it would be clearer just to say that string F1 lies north-south.
I looked at the meridian article, and it seemed ok.
[quote]
.
Is the point O the same as point I ( I think not)
.
[endquote]
I agree. Point "I" will be different from point "O".
[quote]
.
and is the point O (origin of the line segments) orthogonally below the crossing of the wires.
.
[endquote]
.
Yes. The X,Y position of the crossing of the wires is the origin, "O", of the co-ordinate system.
But the point at which the hour lines intersect is point C, different from point O, the origin of the co-ordinate system, directly below the wires' intersection.
Point C is behind (north of) point O. Point C's y-coordinate is negative.
It is around point C, that the shadow-intesection moves at a uniform rate.
[quote]
.
I have the 2 illustration from his article to upload, I assume it is now PD. I would like to do a short example for a London dial(51deg 30) using a N-S wire at 10cm. Michael, why aren't you registered- then I can send you emails and wiki-ping?
.
[endquote]
.
I've just now registered. I don't yet know what wiki-ping is, and so, if a wiki-ping message is sent to me, would I know about it? Maybe, then, if you send one, you should notify me, so that I'll know to look for it.
By the way, I won't build a Bifilar dial, because I'd want the dial to be where it's visible to neighbors and passersby--But they wouldn't recognize the Bifilar as a sundial. Additionally, the Bifilar's disadvantage that I mentioned above argues against it, for a sundial displayed to neighbors and passersby. Besides, I prefer sundials whose construction is easily explained to people.
I'm new here, so forgive me if I'm not familiar with the procedures. What's wrong with just signing with four tilde (~) followed by my name? 65.8.169.50 (talk) 22:20, 8 February 2015 (UTC)Michael OssipoffReply
Latest comment: 9 years ago1 comment1 person in discussion
I've just now edited the Multi-Face Dial section. (and summarized the edits in the Edit-Summary field).
I clarified what the Polyhedral's advantage is, and also its disadvantage with respect to the Horizontal Dial.
The relative advantages and disadvantages of the various dials is something imporant to include.
The already-existing article-section had some discussion of sundial-orientation methods. That discussion needed to be filled-in more. It needed to be more complete.
But I fully realize that, especially in its current more complete form, that sundial-orientation (or alignment) discussion should be in a more general section of the article, rather than a section about one particular kind of sundial (the Polyhedral). ...maybe merged with alignment-discussion already in that other more general section.
The Multi-Face Dial section has a paragraph about faceted dials whose facets are on the inside of a hollow concave space, like that of a Hemispherium or Hemicyclium--a hollow that is roughly cylindrical or spherically concave, except that it's faceted instead.
Such dials must be quite rare. And it's questionable whether they'd have any advantage over a genuinely cylindrical or spherical dial-face. Certainly they have a big disadvantage compared to the usual, convex, faceted dial, the Polyhedral: The Polyhedral can be read (during the right time of day) from any direction, even if the dial is above the person reading it. A concave-faceted dial would have no such advantage. It would merely complicate cylindrical or spherical dial-face sundials, for no purpose or gain.
Because of their rarity, and because they apparently have no advantage (can anyone name an advantage for them?), I suggest that that paragraph be deleted from the article.
Latest comment: 9 years ago3 comments2 people in discussion
It would be alright for the article to be long, if it were more systematic and orderly.
1. Sundials in which the style (shadow-casting edge) consisting of the edge of a hole or slit positioned at the circumference of a cylinder (instead of being at the cylinder's axis) casts a shadow or light-spot on the inner surface of the cylinder:
...a) The article didn't clarify that the cylinder is positioned with its axis parallel to the Earth's axis.
...b) The article should say something about the use and usefulness of such a sundial...the motivation, purpose, advantages ( & disadvantages) or value of the style being on the cylinder's circumference rather than at its axis. In fact, the article's description of cylindrical or conical surface sundials mentions some handheld objects, without addressing the matter of the task of orienting them properly for sundial use.
I propose to make those additions to that section.
2. Analog calculating sundials:
The article doesn't state its principle or give a detailed description.
Internet-search finds no support for the cardioid analog calculating sundial. What is found on the Internet is a number of websites that all repeat the same comments about "analog calculating sundials", always with exactly the same wording.
There are, of course, sundials that automatically correct to give a direct reading of standard time. But there's no support anywhere for the cardioid "analog calculating sundials" described in that article-section and elsewhere on the Internet.
I've deleted the Analog Calculating Sundials section.
I like quite a few other editors are following your changes and developments, and if necessary will edit them again. Can I personally ask one favour could you please not edit the talk page yet as that enables me to follow your train of thought, ideas and proposals. I know it may become bulky but one can either edit it at the end or archive it so that future editors can see how thet article arrived in the form it is in. Thanks Edmund Patrick – confer06:46, 12 February 2015 (UTC)Reply
Sure, based on your clarification about it, I won't edit the talk-page.
I realize that it's best if, before I edit a section of the article, I announce that intention here, in case someone (such as the section's original author) has an argument against the edit. Is that the usual preferred procedure--announcing an intended edit first, for discussion?
A question: In the Multi-Face Dials section, I've expanded the discussion of dial-oriention methods. Clearly that discussion should be in a more general section of the article, instead of in a section about a particular kind of dial. ...But which section should that dial-orientation discussion be moved to? Or should it be a new section, entitled "Dial-Orientation"? I didn't find a section that it seems to go in, so maybe a new section would be best. Comments?
Latest comment: 9 years ago1 comment1 person in discussion
Michael can you please log in- before making a post- it is so much simpler for the rest of use your personal talk page to pass messages and advice- in the same way you use mine.
Brilliant new text- but Wikipedia principles demand it is supported by a reference. For convenience I have added:
The text is littered with {{citation needed}} tags. Certainly any new text must be covered with a citation. The easiest way is to use the {{sfn}} format- this requires a full citation in the Bibliography, we have Waugh, Rohr and Mayall& Mayall already there.
We refer to them by {{sfn|Waugh|1973|p=??}} {{sfn|Rohr|1965|p=??}} {{sfn|Mayall|Mayall|1938|p=??}} . This is now of the highest urgency.
Other references can be written <ref> As much detail as you can give- and someone will work up the format later!</ref>
Text must be written in an encyclopedic way not as a construction manual.
Notation used should be in line with the conventions used by the British Sundial Society Glossary. (adopted by the American Society). Is it?
I am feeling this page is getting too long- and the technical detail in each section could be moved to separate articles. Thoughts?
I am feeling that more formatting care must be taken with out <math></math> sections- as they need to be read on phones, tablet and grown-ups computers- as well as from paper printouts. -- Clem Rutter (talk)17:26, 12 February 2015 (UTC)Reply
Reply to Clem, regarding citations, glossary violations, construction-manual, etc.
Latest comment: 9 years ago2 comments2 people in discussion
Clem:
I’ll use [quote]…[endquote] to mark your text.
[quote]
Michael can you please log in- before making a post- it is so much simpler for the rest of use your personal talk page to pass messages and advice- in the same way you use mine.
[endquote]
I’ve nothing against logging-in. I’ve meant to do so. In fact, I meant to do so this time--but forgot to.
But, even when I sign a post without being logged-in, the “talk” link is at the end of the post. What do you think it links to?
[quote]
Wikipedia principles demand it is supported by a reference.
[endquote]
That’s funny; I didn’t find them. Are they something that’s visible only to you?
I did find _one_ such tag: It was where I said that there was a Universal Capuchin Dial. So I immediately added a line explaining that the Universal Capuchin Dial is described in the sundial book by Mayall & Mayall.
[quote]
Certainly any new text must be covered with a citation.
[endquote]
Incorrect. Here is what Wikipedia says about that:
"Wikipedia's Verifiability policy requires inline citations for any material challenged or likely to be challenged, and for all quotations, anywhere in article space.
"Readers must be able to check that Wikipedia articles are not just made up. This means that all quotations and any material challenged or likely to be challenged must be attributed to a reliable, published source using an inline citation."
So, Clem, are you challenging one or more of my statements, or are you likely to? Then do so.
If so, then you need to be _specific_.
If you think that I’ve said something incorrect, or if you think that something that I said requires verification to determine whether it’s correct, then say so. Share it with us. Don’t be shy.
[quote]
Text must be written in an encyclopedic way not as a construction manual.
[/quote]
My edits weren’t written as a construction manual. To what, in particular, are you referring?
As I’ve already said, in an article on sundials, the advantages and disadvantages of the various sundials is a necessary topic. Some of the advantages and disadvantages involve ease or difficulty of construction. When that’s the case, I’ve stated those advantages too.
[quote]
Notation used should be in line with the conventions used by the British Sundial Society Glossary.
[endquote]
“Notation: A system of characters, symbols, or abbreviated expressions used in an art or science or in mathematics or logic to express technical facts or quantities.”
Did you mean “terminology”? The glossary defines words.
This is the first I’ve heard about a mandatory sundial glossary for Wikipedia.
I don’t know if there exists a self-consistent and complete sundial terminology.
For example, a Polar Dial’s dial-face is parallel to the Earth’s polar axis. A (disk) Equatorial Sundial’s dial-face is parallel to the plane of the equator. But the word “Equatorial” is often used to refer to a sundial whose dial-face surface is a cylinder whose axis is parallel to the Earth’s axis.
That dial’s dial-face is _not_ parallel to the equator.
So, forgive me, but I didn’t know that there existed a self-consistent and complete sundial terminology. But, when I noticed that others were using the word “Equatorial” to refer to cylinder dials with the cylinder’s axis parallel to the Earth’s axis, I began using that usage too, taking it as a convention.
[quote]
Is it?
[endquote]
The fact that you need to ask that tells us that you don’t know of an instance otherwise.
How have I run afoul of the BSS glossary. Be specific.
If you think that I’ve run afoul of proper sundial terminology, then be bold and change the terminology that you think is incorrect in my text. Wikipedia guidelines tell us to not hesitate to immediately correct errors in spelling, grammar, or correct usage.
I looked at the BSS glossary, and of course it’s quite long. Therefore, if you think that I’ve violated it, then you need to specify which part of it you think I’ve violated.
A question: Isn’t it true that Wikipedia stores the text that my edits have replaced, and can easily restore the original text, as it was before my edits?
Latest comment: 9 years ago17 comments4 people in discussion
I've just added some comments to the Reclining-Declining discussion of this talk-page. It's #18 in this talk page's table-of-contents. I don't know if it was proper to add my commments there, or to post them separately in a new separate section. I posted them at the original Reclining-Declining section of this talk-page.
I have a question: People here have mentioned that they have Mayall & Mayall. Would anyone do me a favor, and post, to this section, Mayall & Mayall's formulas for the Reclining-Declining dial?
I feel that I shouldn't ask more, but, if anyone is willing to, and has Rohr's Reclining-Declining formulas, could they post those as well. I emphasize that Mayall & Mayall's Reclining-Declining formulas are my main request in this posting.
I should add that that the correct result described above, with Mayall & Mayall's formula for the angle between the substyle and the line for noon, is gotten when declination (D) is measured from north. ...the azimuth of the direction that the dial is facing.
And, as I said, R stands for the dial surface's inclination from the horizontal.
1. The correct answers I've gotten from Mayall & Mayall's Reclining-Declining formula for the angle between the substyle and the line for noon.
2. The unsupported surprising claim that only in the last decade has there been agreement about how to construct a Reclinig-Declining dial. ...even though Reclining-Declining dials have been around for centuries.
3. The formulas that are't supported by an accessable notable source...
4. The fact that formulas whose derivation isn't explained are a cookbook-recipe construction-instruction--something that I've been told shouldn't be in wikipedia. I don't think people are interested in such formulas, and I don't think they're helpful. Delete them.
...therefore within a week or two, I'm going to delete at least much or most of the Reclining-Declining section, unless support is cited for its claims.
I invite anyone else to supply the citations or do the deletion.
If I delete from that section, of course I'll replace what I delete with something brief.
If anyone disagrees with that proposal, now would be the time to say so, instead of waiting till after I do the deletion.
Additionally: The other of the 2 Reclining-Declining formulas listed in the notes, at the bottom of the wikipedia Sundial article, likewise gives correct answers.
Again, using:
Lat = 51.5
Incline = 45
Decline direction = 45 degrees left of south
...The Mayall & Mayall formula, in the article's notes, for Hrd--gives the correct answer for the angle between the 8:00 a.m. line and the noon line on the dial.
If the line for a particular hour is counterclockwise from the noon line, then that answer might be given as negative, or maybe under some circumstances, as the positive number consisting ofthe sum of that negative + 360.
Let me repeat some things about the use of those formulas:
Where Hrd1 and Hrd2 appear at the left side of the two equations, Hrd1 should be replaced by tan Hrd1, and Hrd2 should be replaced by tan Hrd2.
The equation Hrd = Hrd1 + Hrd2 is correct as shown.
D, the decline direction, is measured from north. It's the azimuth that the dial is facing.
R, the recline, is measured from the horizontal. (Now that's probably more often called "incline" and represented by "I").
So, both of the Mayall & Mayall Reclining-Declining formulas in the notes at the wikipedia Sundial article are correct, and give the correct answer.
I deleted only minimally. I deleted the unsupported and refuted claim that Mayall & Mayall's Reclining-Declining formulas are wrong. I deleted the claim that only in the last decade is there agreement about Reclining-Declining formulas.
For formulas, I referred people to "Mayall & Mayall's classic authoritative book on sundials", and to the British Sundial Society's glossary page (where one can click on "Equations", to find their Reclining-Declining formulas).
I supplied the information needed to use the Mayall & Mayall formulas that the original author included in his note (b).
I stated that the Mayall & Mayall formulas in note (b) are correct and give right answers.
If that sounds like Original Research, then I remind you that the original section-author was claiming (incorrectly) that Mayall & Mayall's formulas were wrong. If it's Original Research to say that the formulas are right, then wouldn't it likewise be Original Research to say that they're wrong? He didn't cite anything when he said that the formulas were wrong, and that unsupported (and incorrect) was claim was left in the article for a long time.
Of course Mayall & Mayall don't need validation. They're an authoritative source, suitable to cite.
As for the original unsupported, unsourced formulas, I didn't delete them, but instead merely stated that they aren't guaranteed to be correct.
The article should also state that, because note (b) left out Mayall & Mayall's formulas for the orientation of the style with respect to the dial-plane, and because the "tan" that should have been in front of Hrd1 and Hrd2, where those quantities were alone on the left side of their respective equations, therefore it can't be guaranteed that something else isn't left out of note (b).
Hi Michael. I just took a look at Waugh's book. (See citation list in main article.) In Chapter 12, page 106, he discusses "Dials which both decline and recline". Basically, he says that calculating the design of such a dial is a horrible problem, and that it's easier to lay out the hour lines by experiment and observation. Let the Sun show you where to draw the lines. The availability of computers would make the calculations easier for us than for him, but even so experiment is probably the better way to go. He says that in the 19th Century, Encyclopedia Britannica gave full trigonometric formulas for the calculation, but dropped them before he wrote his book (1973), apparently because they were deemed too complex for practical use. DOwenWilliams (talk) 04:11, 7 April 2015 (UTC)Reply
Hi Don--
You're oh so right about the unsuitability and undesirability of a highly technical section full of formulas!
In fact, I've just logged in for the purpose of deleting the formulas in the Reclining-Declining section. I'm glad that there's agreement with that. I'm glad that someone seconds the motion.
Clem was right when he said that that section looks more like a college course. ...except that it doesn't have any derivation for the formulas.
Sure, other sources often give formulas without derivation, and without any clarity for readers about the formulas' derivation. That's their business, but I think we all agree that that isn't suitable for an encyclopedia.
I'm not saying that technical is wrong, per se. It would be ok if derivation were presented...except that that isn't really something that our intended audience wants.
So I'm going to delete all the formulas in the Reclining-Declining section. I'll do that right after I post this.
And then, next will be the formulas in the vertical declining section. ...for the same reason. I'll do that deletion tomorrow.
And what about the Reclining section? Well, for south reclining dials, just explain it by pointing out that it's the same as if the dial were at a different latitude, and so the dial is drawn as if it were at that latutide.
Likewise for vertical north or south dials.
For vertical east or west dials, it's just a polar dial.
If anyone reverts those deletions, then they must be doing so because they want Wikipedia to be a construction-instruction cookbook, giving technical formula instructions without derivation.
Thanks for expressing agreement with what I'm doing.
P.S. Of course the Mayall & Mayall formulas in note (b), in the notes at the end of the article, still remain, as do my comments about their accuracy and their use.
Anyone should feel free to delete that too, if desired.
It's enough to recommend that someone who wants formulas can find them in Mayall & Mayall, or at the British Sundial Society glossary-page, by clicking on "Equations" there.
Disagree- but as I am on the road I haven't time to enter the who was right stakes. The test for me is if someone says to me "Is this this dial accurate? I can come to this article and obtain the necessary formulae to run the equations through a spreadsheet to replicate the dial. I don't carry Waugh and friends- or my BSS publications with me on my phone. With all this tender loving care it looks like we can spin off a few separate sub articles very soon. I will look again soon. -- Clem Rutter (talk)12:29, 7 April 2015 (UTC)Reply
Clem says:
[quote]
Look clearly at the footnotes.
[/quote]
What note in particular? You (or whoever initially wrote the statement) didn't specify a source for these statements:
"In fact it is only in the last decade that agreement has been found on the correct hour angle formula for this type of dial [...] Previous formulae given by Rohr and Mayall are not correct."
That's quite a claim to make without citing a source.
But, if you can't do that, then why can't you show an example in which Mayall & Mayall's formula (In Mayall & Mayall's original form, without the omissions in your note (b) ), give a result that is contradicted by other formulas from authoritative sources?
Are you referring to your reference 43? Is that Compendium issue the place where (according to you) an article can be found that says:
"In fact it is only in the last decade that agreement has been found on the correct hour angle formula for this type of dial [...] Previous formulae given by Rohr and Mayall are not correct."
...?
If so, then say so. And quote the actual statement that you're referring to, if there is one.
The Compendium article that you cite isn't available on the Internet. Convenient for you.
But that's why you need to quote the brief passages that make the statements that youu (or the original poster of that article-section) made, and which I quoted above, in quotes.
If you can't do any of the above-requested things, then your claims in quotes above are unsupported.
Likewise, for that matter, you didn't clearly specify where you formulas (the ones you represent as correct) came from. It would be good to tell that.
Below, you say that you didn't have time to check the math. Well, I checked Mayall & Mayall's formulas (the ones in your note (b) ), and they give correct results.
Whoever copied Mayall & Mayall's formulas into your note (b) made some omisions. He left "tan" out, where it belongs in front of two quantities. He neglected to clarify that those formulas take D to be measured from north (clockwise), and R to be measured from the horizontal.
When those fixes are made, Mayall & Mayall's formulas quoted in note (b) give correct results, right down to the caculator's last decimal place, for the following example:
Latitude: 51.5
Recline (as defined above) 45
Decline-Direction: 45 degrees left of north
...(That's D = 135, as D is defined above)
For the following times of day:
8:00 a.m. and noon.
Additionally, of course, Mayall & Mayall's formulas give the correct results for a horizontal dial too.
If you know of an example in which Mayall & Mayall's Reclining-Declining formulas (in their original form, as opposed to someone else's mis-copied version), give results that area contradicted by formulas from another authoritative source, then feel free to share it with us.
The reference that interest me most is this Marchs NASS Compendium Vol 13 3 but I certainly haven't had time to check all the maths. But the reference has been there in our article though without the Wikilink- (I will put that in now). In looking for this I came upon the hosts document list. There is plenty of reading there- Sundial articles from the NASS and plenty of potential articles. BSS and NASS are both notable respected sources.-- Clem Rutter (talk)19:53, 7 April 2015 (UTC)Reply
Clem: If you're on the road, and don't have time to justify your actions, then maybe you also don't have time to do actions that you don't have time to justify.
As you well know, reverting an edit without giving justification is considered vandalism.
The statement that Mayall & Mayall's Reclining-Declining formulas are wrong is completely unsupported. Likewise the statement that only in the last decade has there been agreement about how to make a Reclining-Declining dial.
I told why I deleted those statements. You didn't tell why you re-posted them. Mayall & Mayall is a respected authoritative source.
When you say that they're wrong, you need to support that statement.**
You said in your edit-summary:
[quote]
(I disagree - the maths is more important than comment...
[/quote]
What does that mean? Cookbook instructions without any derivation, and without citation?
[quote]
, the reader must be able to follow the argument with out looking at other references.
[/quote]
What argument? The text that you've re-posted contains no argument or derivation to support the formulas.
Additionally, our audience has no wish for elaborate formulas, with or without derivation.
[quote]
Slow down on this one.)
[/quote]
Yes, there's certainly no point trying to help you if you revert my edits without giving any justification, and if you mechanically, robotically, and arrogantly re-post surprising, unsourced and incorrect claims without citation. ...in blatant violation of wikipedia's stated policies.
"Slow down?" How about stop trying to help you.
I invited dialists at a sundial mailing-list to help fix the wikipedia Sundial article. Inexplicably (or so it seemed at first) no one there wants to participate here. Now it's clearer why that is. Best to just let you wikipedists, who don't even follow your own rules, muck up your articles as you wish. ...because that's what you'll do anyway.
Help with the article is requested at the top of this talk-page. I tried to help. I did my part. What someone else does afterwards isn't my responsibility or concern.
I find it interesting that Waugh, whose book is one of the most widely respected and used on the subject, doesn't include any formulas for designing a declining-reclining dial. He just advises doing experiments, citing Encyclopedia Britannica's precedent. Maybe we should ask whether Wikipedia should include formulas, if Britamnica deliberately omits them.
Personally, I think that the only sensible way to solve this problem, other than by experiment, is to write a computer program which would start with a simple dial in a simple orientation and then approach the desired case by using a composition of simple rotations. I've used this approach for similar problems in the past. It works just fine. The machine ends up doing rather more calculation than is strictly necessary, but it gets the right answer very fast by human standards. However, we can't explain this method in this article, since putting computer code into Wikipedia is a no-no, or so I've been told in the past when I've tried to do it. Besides, it is rather unconventional, and finding citations for it would be difficult.
And experiment has another use: If someone wants to claim that a set of formulas is incorrect, then they can verify (or fail to verify) their claim by marking a dial face and place the style according to the formulas. They need only draw one or a few of the lines, for the purpose of the experiment. Then place the dial in the orientation for which they made it, and find out how accurate the resulting dial is.
Actually, that experiment has already been done, for Mayall & Mayall's formulas. They've been published for so long that, if they were producting inaccurate sundials, that would have been noticed long before now.
Of course there's another way that, if Mayall & Mayall's formulas were incorrct, Clem could demonstrate it: He could cite an example (a latitude, a reclilne, a decline-direction, and a time of day). He could then show that Mayall & Mayall's formulas give a different answer than that given by another respected authoritative source, such as BSS. As I said, BSS's Reclining-Declining formula can be found at BSS's Glossary page, by clicking on Equations, at the top of that page.
Or does Clem think that BSS is wrong too? ...and maybe that everyone is wrong, except for his unsourced set of formulas? Then, as you suggested, experiment is the test.
Waugh doesn't suggest using experiment to falsify or support theoretical formulas, although of course it can be used for that. He suggests using experiment instead of formulas, making complex math unnecessary. If you want to put a sundial on a sloping roof, just erect a gnomon parallel with the earth's axis, then mark the positions of the shadow of the gnomon on the roof at hourly intervals for a day. That's all! What could be simpler?
Long ago, I wrote a computer program called Sunalign which calculates the orientation of a heliostat mirror at any latitude and longitude, any time and date, and to reflect sunlight in any desired direction. I used it in the software of a real computer-controlled heliostat that I used for daylighting my house. It worked just fine. Of course, this problem is related to the design of a sundial. I posted Sunalign on a website called www.green-life-innovators.org, along with some explanatory text. As far as I know, it's still there.
Latest comment: 9 years ago5 comments3 people in discussion
Sun Align is still there. I think a port into Python would bring it into 2015- and then it sounds like a winning Raspberry Pi project for some student with a little time!-- Clem Rutter (talk)23:37, 7 April 2015 (UTC)Reply
Anyone is welcome to port as they please. The program has been public domain for a quarter century.
If you look at the code of Sunalign, you won't find much resemblance to the formulas that are used for designing sundials. It uses a conceptually different approach. I taught high-school math for a while in the 1970s and 80s, and wrapped my mind around the "transformational" methods that were then used in the teaching of geometry. Instead of static figures, as used by Euclid, these methods use motions of elements to transform shapes into different forms. I found I could use these ideas, in three dimensions, to write programs that would do interesting things like heliostat calculations. Sunalign contains subroutines that rotate things in space. Rotation is a basic transformational operation.
The lesson from this is that there is no unique "right" way to do these calculations. You may have one set of formulas and someone else may have a different set, but they may both be completely correct and useful. The choice among them may depend on the technology that will be used to solve the problem. In the 19th Century, people used pencil and paper, and looked up trig ratios in published tables. Calculations were tedious. Now, we use computers. We don't care if the machine takes an inefficient route to solve a problem. A program like Sunalign does a lot more calculating than a 19th-Century mathematician would have done, but so what. It takes a few milliseconds longer. Big deal. The important thing is that the algorithm is easy to understand and the program is easy to write.
Yes, the direct empirical marking of Reclining-Declining dials, suggested by Waugh, is a feasible procedure. It seems to me that its desirable that anything that one is offering for use by other people, including a sundial, should be easily explainable to them. So Waugh's empirical-marking suggestion is good, as an explanation, as well as an actual procedure.
I used to believe that a human-gnomon sundial would be good for public places, like a downtown plaza, but I wouldn't suggest one now, because I prefer things that are understandable to the public.
For the same reason, I've had doubt about the desirability of a declining flat dial (whether reclining or vertical), because it isn't easily explainable to people--whose encounter with it might be unfavorable for that reason.
But, as you pointed out, a Reclining-Declining sundial has a good, simple, easy procedural explanation: Empirical-marking.
Before you mentioned it, I hadn't known that Waugh suggested that. Thanks for pointing that out.
As you also pointed out, problems often have various different solutions. It's easy for someone to bigotedly start proclaiming that all solutions other than his own are wrong, because the various formulas look different from eachother.
Here, quoted below, is an example of such bigotry:
"In fact it is only in the last decade that agreement has been found on the correct hour angle formula for this type of dial [...] Previous formulae given by Rohr and Mayall are not correct."
Does that sound familiar? It's in the wikipedia Sundial article. Not only is it without citation, but it's also incorrect. ...demonstrably, preposterously so.
I deleted it. Clem re-posted it.
I suppose that, most likely, Mayall & Mayall are long-deceased, and so the abovequoted mis-statement isn't a problem to them.
To whom would it be a problem then? Well, to someone who cares about the quality, accuracy and reputation of the article, and of wikipedia in general.
I couldn't care less if Clem wants this wikipedia article to be a laughing-stock, to dialists.
I couldn't get any dialists to participate here, and it's clear enough why.
I've just now deleted most, or nearly all, of my text in the wikipedia Sundial article.
With its unsourced incorrect statements that I refer to above, your article is so shabby that it would be too much of an embarrassment to be involved with it in any way, with any amount of participation.
So, in the sections where I'd edited, restore what you had before my initial edits.
Take it easy, Michael. Wikipedia isn't worth getting upset about. By its very nature, it is, always has been, and always will be riddled with errors. Whenever I read an article about a subject that I know well, I find errors, sometimes serious ones. When I try to correct them, some brat vandalizes what I write.
I have a stepdaughter who was recently a student at the University of Toronto. I mentioned to her that I edit Wikipedia, which she hadn't known previously. She looked at me in horror, and said that the professors had told the students not even to look at Wikipedia, and that anyone who cited it in an essay or other paper would have marks deducted for doing so. They had a point.
And yet Wikipedia is very widely read and used. I continue to edit it because I don't want too many people to be too badly misinformed. Perfection is impossible here, but the level of disinformation may be reduced - I hope.
I don't think that's legal. Once you've put something into the public domain, you can't just grab it back again. But don't worry. I doubt very much that they'll want to use it. DOwenWilliams (talk) 23:26, 9 April 2015 (UTC)Reply
Michael: What you've done is to revert all edits that have been made since 30 December, including some that were not done by you. If you just want to revert your own edits in the declining-reclining dials section, you should take the text of that section from the 30 Dec version and paste it into the current version, leaving everything else alone.
My edits in Reclining-Declining were already deleted by Clem's reversion.
What I did was: First I deleted my text in the other article-sections that I'd edited, and there was a fair amount of text to delete.
But I felt that I had a responsibility to restore what I'd replaced. That seems only fair. So I restored the version that was up before my first edits.
I didn't know that others were editing during that time. If they did, did they mention it at the talk page?
The only edits by others that I'm aware of during that period were two that reverted some of my edits.
Just deleting what I'd posted would have the problem that it wouldn't restore what I'd replaced when I initially put up my edits.
Oh, ok, I could have (as you said) pasted from the 30 December version, to replace the particular sections where I deleted my text. But of course deleting and pasting whole sections could still eliminate someone else's edits made to that section during that period.
Latest comment: 9 years ago16 comments3 people in discussion
Clem:
I'm not trying to be difficult, argumentative, or critical of you. I'm just trying to get you to say, more clearly, where you got the statements quoted below.
I'll refer to the two statements quoted below as "the quoted statements":
"In fact it is only in the last decade that agreement has been found on the correct hour angle formula for this type of dial [...] Previous formulae given by Rohr and Mayall are not correct."
When I asked before, you said to read the notes. ...But which note in particular?
The only citation given in your text, anywhere near to the quoted statements, was citation #42, a referene to a Compendium issue.
So, Clem, are you saying that the Compendium issue referred to in citation #42 is a source of the quoted statements?
Yes or no?
And, if not, then where, exactly, is the source of the quoted statements?
It isn't an unfair question.
I want to clarify that before I start asking people for information about that issue of Compendium.
Can you give an example (consisting of a latitude, a recline, a decline-angle, and a time of day) in which Mayall & Mayall's formulas (their original ones, not someone's miscopied version) give a result that differs from other long-established authoritative sources?
If you can't, then should you be making the quoted statements?
Let me say this again here:
Your note (b) misquotes Mayall & Mayall's formulas, in the following ways:
1. It leaves out "tan", where it belongs in front of two quantities. (Hrd1 and Hrd2, where they each appear alone on the left side of an equation).
2. It fails to define D and R, as used in the formulas, where:
...D is measured from north (clockwise).
...R is measured from the horizontal.
With those two fixes, Mayall & Mayall's Reclining-Declining formulas, quoted in your note (b), give results that are correct, right down to the calculator's last decimal-place.
3. You (or whoever wrote that section) left out Mayall & Mayall's formulas for the dial-orientatation of the style.
Of course there might be more that was omitted as well, in note (b).
Here, again, is the pair of examples in which Mayall & Mayall's formulas gave the correct answer:
Lat = 51.5 ...
.
Recline = 45 ...
.
Decline-Angle = 45 degrees left of South (that's D = 135)...
.
Time of Day: 8:00 a.m, and noon
Some wikipedians care about wikipedia's principle regarding citations. Let's get to the bottom of this. What's the source of the quoted statements?
I agree with you about wikipedia's citation and notability policy.
And, if Clem could supply good OR to support the quote statements, that would be fine (but I can't speak for wikipedia on that).
That OR would best take the form of an example in which Mayall & Mayall's Reclining-Declining formulas give the wrong answer (in comparison to that of other well-established, respected, authoritative sources).
...And (to verify the 2nd statement in the quoted statements) an instance of any two different well-established, respected authoritative sources' formulas contradicting eachother, before the last decade.
But of course it would also be fine if those examples were gotten from other sources, as opposed to being Clem's OR.
I agree that it would have been nice if Clem had cited his source(s). Presumably, he got his formulas from somewhere. He should have told us where. However, if he just copied them from a book, that wouldn't have been convincing to me. Books are depressingly often wrong. What could have convinced me would have been a proof. This is all simple trigonometry. The formulas must be derivable from basic principles. If Clem derived them, then it would be nice if he showed us the derivation. If he read a published derivation, then I'd like to know where to find it.
If I were feeling less lazy, I'd try deriving them myself. After all, this is just a sundial problem. It's trivial compared with, say, the heliostat problem.
Do Mayall & Mayall give a proof of their formulas? If not, I'm just as sceptical about them as I am about Clem's. Sure, they've been around for 77 years without being proved wrong (except, perhaps, by Clem and his sources), and in some simple cases they give exactly the same answers as simple formulas suited only to these cases, but these don't amount to undisputable proofs.
Where are the proofs?
Of course, it is possible that the two sets of formulas may be equivalent. It may be possible to interconvert them, using trigonometric identities. Alternatively, bearing in mind Godel's incompleteness theorem, it is possible, but unlikely, that they may both be correct, in the sense that they always give the right answers, without being interconvertable.
Let me just answer or comment regarding a few points. Maybe it's more orderly or convenient if I number them:
1. Quite so. Juat citing a book or an article doesn't prove anything. That's where Wikipedia policy is wrong. But of course if it's a book that has been in use since the '30s, and it's formulas have been used for making many Reclining-Declining sundials, that counts for something.
Still, if Clem could at least cite _someone or something_, for the quoted statements, then at least one could contact his source, and ask them how they justify the statements. That would be an improvement over what he's doing now--putting up something that he can't even source.
Sure, a mathematical proof, or a derivation, would be good, but I'd settle for less. Agreement with formulas from other respected authoritative sources would be good. As I've been mentioning, I checked the Mayall & Mayall formulas for giving the right answers, and they did fine. Let Clem test his formulas, and report that they give the same results as formulas from some respected authoritative source. He's the one who re-posted them, and so it's his responsibility to verify them, or at least in some manner show some reason to believe that they're correct.
You wrote:
Do Mayall & Mayall give a proof of their formulas?
[/quote]
Probably not.
You wrote:
If not, I'm just as sceptical about them as I am about Clem's. Sure, they've been around for 77 years without being proved wrong (except, perhaps, by Clem and his [unspecified] sources)
[/quote]
I'm not saying that's proof, but it tends in the direction of some confirmation. That and the fact that Mayall & Mayall are considered a classic authoritative source.
You wrote:
, and in some simple cases they give exactly the same answers as simple formulas suited only to these cases
[/quote]
Yes, they give the right answer for a horizontal sundial. But they don't only give the right answer for simple or special cases. They give the right answer for a reclined and declined sundial too. ...for noon and 8:00 a.m. 8:00 a.m. was an arbitrarily-chosen time, and not a special or simplified case, in any way.
Even noon probably shouldn't be considered a special-case for a reclined-declined dial.
If the Mayall & Mayall formulas were wrong, then it would be vanishingly improbable for them to give the right answer for an arbitrarily reclined and declined dial, for the arbitrarily chosen time of 8:00 a.m. ...and then also give the right answer for noon as well. ...with those answers being correct right down to the last decimal place on the calculator.
True, that isn't a proof, and it isn't the same as showing the derivation of the formulas. Mayall & Mayall probably used formulas that were already widely accepted by dialists or in academia.
Not a proof, but still compelling. ...certainly enough to bring Clem's quoted statement into doubt.
So, I'm not asking Clem for a proof or derivation. Only for a source. ...&/or for Clem to try his formulas out, and find out if their results are the same as those of the BSS formulas, for example.
I, or anyone else, shouldn't have to check and test the formulas that Clem chose to post. It's his responsibility to tell of some reason why they should be trusted.
But I'm also asking Clem if he can (or can't) tell me whether or not the article's citation #42 is the source for the claim that the Mayall & Mayall formulas are wrong, and that there wasn't agreement re: Reclining-Declining formulas till the last decade.
It's a simple Yes/No question.
And, if that isn't the source for it, then what is?
I'm not saying that Mayall & Mayall's longtime respectedness means it's right. But, even just by itself, it certainly means that Clem needs to at least specify a source if he wants to say that it's wrong.
And is there some reason why he doesn't want to show an example in which the Mayall & Mayall formulas give an answer that's contradicted by formulas from another respected authoritative source?
The more something is called a "respected authoritative source", the more suspicious of it I become. People don't like criticizing such sources. Sometimes, they even bend the truth to make them seem better than they are. Sure. M&M's formulas are ancient, slightly more ancient than I am, but that doesn't make them more likely to be true. The biblical texts on which the prosecution of Galileo was based were also very ancient, and illogically revered.
I still want proofs, of M&M's formulas, of Clem's, and maybe both.
But this really doesn't matter. Using the formulas is just conceit. The sensible method is by empirical experiment.
I completely agree with the words that I quote directly below:
The more something is called a "respected authoritative source", the more suspicious of it I become. People don't like criticizing such sources. Sometimes, they even bend the truth to make them seem better than they are.
[/quote]
Regarding the formulas: I tried to delete the formulas. Clem re-posted them.
I tried to delete them because:
1. Formulas aren't right for the article, and no one wants them.
The article shouldn't look like a highly technical page from a college textbook (but a textbook, unlike Clem's text, would at least show derivation of its formulas).
2. Clem (and whoever initially posted those formulas) chose to not tell their source, and is unable to show an example in whicy they give the right answer.
I want to disclaim that, though I fixed errors in the miscopied formulas in note (b), of course I can't guarantee that note (b) doesn't have other omissions too. For example, note (b) doesn't give Mayall & Mayall's formulas for the dial-orientation of the style. What else does it leave out? Something that will cause it to give a wrong answer under some conditions? I can't guarantee otherwise.
So, though I feel that, if formulas are recommended, then Mayall & Mayall's own version of their formulas can be recommended, that can't be said for note (b).
But I agree with you, in not recommending formulas for the article.
If someone likes them, that's diffrent. If so, then they won't want formulas wthout derivation, or need me, Clem, or the article to give them formulas as a cookbook-recipe construction-instruction.
And most people don't want formulas. Empirical determination is the right construction explanation for the article.
You and Clem are almost certainly the only people who read the formulas in detail (note that I don't include myself), and you do so only because you both think you know the correct formulas already. This is a big fuss about nothing. Forget it. Get back to real life. DOwenWilliams (talk) 14:20, 11 April 2015 (UTC)Reply
David--
You wrote:
You and Clem are almost certainly the only people who read the formulas in detail
[/quote]
What? I read note (b)'s version of Mayall & Mayall's formula in order to try it on examples. I did that to check the accuracy of Clem's statement (If not originally Clem's, it was his after he re-posted it) about Mayall & Mayall being wrong.
Forgive me, but I thought that accuracy was considered relevant at wikipedia.
And no, there's no reason to believe that Clem read his formulas in detail. He didn't report an example in which they gave a right answer. He has no idea of whether or not they work, or what their source is.
You wrote:
, and you do so only because you both think you know the correct formulas already.
[/quote]
Incorrect. That isn't what investigation is about. It's about finding out what the facts are, or at least getting information that strongly implies something about them.
Yes, the widespread assumption is that Mayall & Mayall's formuls are good. But I didn't assume it. I tested it.
My tests confirmed the trust and respect for Mayall & Mayall, and contradicted Clem's claim.
Note that "confirm" doesn't mean "prove". But, though miscopying in note (b) could result in wrong answers under some conditions, the correct answers from Mayall & Mayall's formulas, in note (b), with arbitrarily-chosen latitude, recline, decline-angle and time-of-day--makes it vanishingly unlikely that Mayall & Mayall's Reclining-Declining formulas are incorrect in any way. (...in Mayall & Mayall's own version, as opposed to note (b)'s miscopied version).
You wrote:
This is a big fuss about nothing.
[/quote]
...only if you think that accuract at wikipedia is "nothing".
And I don't know why you're criticizing me about formulas. I was the one who said that they don't belong in the article, and tried to delete them.
(Clem re-posted them, vandalizing without giving justification).
I tried. It's your turn. If you don't like the formulas (especially unsourced and unsupported formulas and statements) in the article, then, instead of complaining at me, you can do what I did: Delete them.
Have you compared Clem's formulas with the M&M ones? They may be almost the same, with a little tweak someplace that only rarely makes any difference. DOwenWilliams (talk) 19:12, 11 April 2015 (UTC)Reply
Testing Clem's formulas is Clem's responsibility. If he doesn't want to try them out, via an example, then let's let them remain un-tested, instead of doing Clem's job for him.
Testing a new formula can be a bit of work, because the definitions of the variables, the conventions and assumptions, and the interpretation of the formula aren't always obvious.
Clem wants to post it, let him test it instead of doing his work for him.
I find it hilarious that the wikipedians are leaving Clem's unsourced, unsupported formulas and statements in the article. What a shabby organization, with no regard for its principles, policies and rules.
Well, in this section my posts weren't addressed to you. Butting-in, as it were, with posts mostly unelated to my topic, you immediately replied, unasked, to my first posts in this section. Fine, but then you began typical Internet-troll attack-behavior, without provocation. I hadn't said anything hostile or impolite to you.
So opt out by all means. Better had you not opted in.
As for Clem, I remind you that my initial post in this section (which was to Clem, not to you) was entirely polite. I emphasized that I didn't want to be critical, but I just asked some simple questions about his source for the "quoted statements" and his formulas.
Clem opted out as soon as I politely asked those questions. What Clem opted out of was answering simple questions about the source of the "quoted statements", and of his formulas; and showing an example in which Mayall & Mayall's formulas give an answer that's contradicted by formulas from some authoritative source.
I didn't say anything critical till Clem didn't answer the simple questions. ...and until you began your unprovoked Internet-abuser manners.
Ok, so it's alright to blatantly disregard and violate the wikipedia principles, policies and rules that wikipedians espouse, but it's a no-no to point that out?
I'm not the only one who expresses disappointment in the wide gulf between wikipedia principle/policy, and wikipedia practice and conduct. I'm not the only one who expresses a low opinion of that.
Anyway, the lack of decorum began with your flamewarrior behavior during the conversation that you began when you joined the discussion unasked.
And, DOwenWilliams, there's no need for you to continue posting to this section, or to continue this conversation--just as there was no need for you to start.
My questions were to Clem Rutter. I let you start a conversation, and was polite enough to reply, but I didn't then and don't now have anything to say to you.
And Clem: If you don't want to answer those brief and simple questions, politely-asked, suit yourself. That, itself is an answer.
I've just deleted un-sourced, completely unsupported text in Reclining-Declining. Ref #42 doesn't support any of that text. No valid citation is given.
Latest comment: 9 years ago2 comments1 person in discussion
I obtained the Compendium article referred to in Ref #42. It doesn't mention anything about Mayall & Mayall's formulas, or Rohr's formulas, being incorrect. Nor does it have the formulas that Clem re-posted.
The material that I deleted was entirely un-sourced, not supported by any citations, not supported in any manner.
I found the Compendium article Sundial Design Using Matrices, and that, too didn't mention the alleged incorrect formulas of Mayall & Mayall or Rohr, or the formulas that Clem re-posted.
The material deleted was entirely un-sourced, not supported by any valid citation. Surprising or implausible claims espectially neec citation.
Wikipedia has a policy against construction-instructions in an encylopedia. That's what formulas without derivation are. A cookbook impersonating a technical textbook--except that textbooks have some derivation of their formulas.
The Compendium issue that the reference, Ref #42 in the pre-deletion text, referred to did not contain the article referred to (Sundial Design Using Matrices). It had a different article by the same person who wrote Sundial Design Using Matrices. The article Sundial Design Using Matrices was in a different issue of Compendium.
But neither of those two articles by that person, in Compendium, mentioned anything about the formulas of Mayall & Mayall or Rohr being incorrect. Neither said that only in the last decade has there been agreement about how to mark Reclining-Declining dials.
In other words, as I said, the contested two statements, in the article version that Clem wants to keep, have no valid citation, and are entirely un-sourced.
That's true as well for the formulas in the section-version that Clem re-posted.
By Wikipedia's principles, policies and rules, I had every justification for deleting the text that I deleted today. There is no justification for re-posting it.
Latest comment: 9 years ago1 comment1 person in discussion
The subject line says it all.
Indeed, Clem's Ref 43 has Reclining-Declining formulas. The problem, for Clem, is that the article's formula for an hour-line is quite different from the one in the article-version that Clem keeps re-posting.
Clem, you can't use a formula as a supporting citation, when it doesn't resemble the formula that you're trying to support.
The cited article also doesn't have Clem's formulas for the dial-orientation of the style.
And the cited article also doesn't contain the statement that Mayall & Mayall's Reclining-Declining formulas are wrong, or that it's only in the last decade that there's been agreement regarding the marking of Reclining-Declining dials. (I'll refer to those statements as Clem's "controversial statements").
In summary, the cited article, Ref 43, doesn't support Clem's formulas or his controversial statements.
It doesn't lend any support to Clem's article-version.
Latest comment: 9 years ago2 comments1 person in discussion
Clem:
You have made a vague reference to an article in which Snyder summarizes Brandmaier, (available from NASS for $6.50).
I ask you three questions about that:
1. Is that, your latest vaguely-implied reference, something other than Compendium 22:1, March 2015, "Sundial Design Considerations", by Snyder?
2. Does it contain or support your implausible controversial statements? (By which I refer to your statement that the Reclining-Declining formulas of Mayall & Mayall are incorrect, and your statement that only in the last decade has there been agreement on how to mark a Reclining-Declining dial)
2. Does it contain the Reclining-Declining formulas that you keep re-posting to the Sundial article? (...in the literal same form, not some other formulas to which you claim that yours are equivalent)
To justify your latest reversion, your re-posting of your deleted text, you need to start by answering the above 3 questions affirmatively (if such an answer would be truthful).
If you answer affirmatively, then I'll check to find out if that answer is truthful.
If you answer negatively, then you're admitting that you still haven't justified the deleted text that you've re-posted, and that you are continuing to re-post un-sourced material, without any valid citation.
If you don't answer, then it must be assumed that your reference to Snyder is Compendium 22:1, March 2015, "Sundial Design Considerations", which I've already checked,and which does not contain the formulas that you re-posted. ...or that, whatever else you're referring to, it doesn't support your re-posting of your questionable deleted text, and that your latest reference is just as phoney as your references #42 and #43.
Given the falsity of your vague implication that your Ref #42 and Ref #43 supported your deleted text, surely you must understand that it's not unfair to ask you these simple Yes/No questions regarding what you're explicitly claiming about Snyder's alleged support for your questionable text.
Clem could also verify one of his implausible statements by showing an example in which Mayall & Mayall's Reclining-Declining formulas give a wrong answer.
Likewise Clem could also verify his formulas by showing one example in which they give a right answer. (I'd then check for an example in which they give a wrong answer.)
If Clem regards his formulas as so difficult or so much trouble that he doesn't want try them out on an example, then how can he think that they should be in the article?
I'm just offering Clem these additional ways to show that his questionable, un-sourced, text is valid.
Latest comment: 9 years ago3 comments2 people in discussion
1. The statement that the Reclining-Declining formulas of Mayall & Mayall, and Rohr are not correct lacks a citation. In the case of Mayall & Mayall, the statement is incorrect. Mayall & Mayall's formulas give the right answer for an example with arbitrarily chosen latitude, recline, decline-direction, and time-of-day. Additionally, Mayall & Mayall's formulas are correct when applied to a horizontal dial.
Admittedly, whoever copied Mayall & Mayall's formulas into note (b) made a number of copying-errors that would result in wrong answers, if not fixed. But that's the fault of the person who copied them into note (b), not of Mayall & Mayall.
As for Rohr, I have no idea whether or not his formulas are correct. But, in any case, a citation is needed for such a claim--when contradicting a long-established classic authoritative source. Clem said or implied that there's a book that supports the statement that (at least one edition of) Rohr's book gives incorrect Reclining-Declining formulas. But Clem's citations have a really poor accuracy-record.
2. The statement that only in the last decade has there been agreement on how to mark a Reclining-Declining dial is likewise without any valid citation. ...is completely un-sourced.
3. It's necessary for the reader to be warned that the formulas currently in the Reclining-Declining section are of unknown origin. It's bizarre that Clem thinks that that the reader doesn't have a right to that information.
Clem deleted the warning when I added it before, and I've restored it to the article.
Clem says that someone deleted the references, and then complained that the text was un-referenced. No, the statements that I deleted again today were unreferenced. And the formulas are, and always were, without any valid citation.
Wikipedia policy requires that if your text is deleted because it lacks citation (especially if it's controversial), then you must not re-post it to the article. Clem violated that rule when he re-posted his un-sourced statements, today, and on all the previous occasions when he did so. Likewise when he re-posted his un-sourced formulas.
The purpose of this message is to explain the justification for the edits that I did today. ...the ones specified above in this messaage.
Wikipedia requires an explanation of reverts. That's another wikipedia requirement that Clem doesn't bother abiding by.
If Clem has a book that says that Rohr's formulas were wrong, then he should cite Rohr when he makes that claim.
Was there a reference, regarding the Rohr-incorrect claim, that I didn't notice? If so, then my apologies. If there already is/was such a citation, then of course put the claim about Rohr back in the article.
But don't put the one about Mayall & Mayall back in, unless you have a citation for that. ...or an example in which Mayall & Mayall's formulas give a wrong answer.
Clem has been blatantly and knowingly violating wikipedia policy, giving readers at least one un-sourced false statement regarding a classic authoritative source, and a set of formulas of unknown origin.
"Any material lacking a reliable source directly supporting it may be removed and should not be restored without an inline citation to a reliable source."
Of course Clem has been blatantly disregarding that policy.
Latest comment: 9 years ago3 comments3 people in discussion
...and I've just restored the fixed version that the administrator had put up.
The version that has a template announcing the Reclining-Declining section's un-sourced material, and the tag identifying the formulas as possible original research.
That administrator advised me that warnings such as the one that I'd added (about the formulas of unknown origin) should be given in the form of a template instead of by adding text as I did.
Then Clem reverted that administrator's fix.
As I said, I've just now restored it.
That restoration removes the un-sourced and demonstrably false statement regarding Mayall & Mayall, as well
Thanks, Neil. If the page was ever stable enough long enough that could happen. We need to go back to Davids version before we have any hope of adding. vI have given him a lot of help on his talk page- which was subsequently deleted- and given him the primary source that supports the statement. I now have received the disk from the NASS with 21 years of primary sources. I am restoring the page that had evolved User talk:ClemRutter#Reclining-Declining Sundials in April 2014 but copying the page (that I basically commenced in 2008 ish) that MichaelOssipoff is so keen on into a sandbox so he cam demonstrate his ideas. See User talk:MichaelOssipoff for dialogue. I hope that lasts long enough so we can actually introduce some better references. Please feel free to contribute- or not.-- Clem Rutter (talk)15:14, 27 April 2015 (UTC)Reply
Latest comment: 9 years ago3 comments2 people in discussion
We have a new problem- hundreds of new references and sources. I took some of the advice that I have been generously giving out and purchased a cd-rom containing backcopies of the North American Sundial Society's journal, Compendium. Yes it cost ₤18.00UK. There are 21 years worth of quarterly journals, all superbly references and illustrated, together with links to other important sources- the index alone runs to 30 sides with an average of 40 lines on each!
I advise everyone reading this page to purchase a copy: Back Issues Repository- we certainly never will need to hunt for a reference again. The danger is that it is just as addictive as Wikipedia.
I keep looking at it and hesitate- I need to rewrite it, it is far too bloated and there are rolling implication. But a direct question- a direct answer. The changes were started by User:Tamjk corrected the formulae on 10 April 2014. I had a conversation on my talk-page User talk:ClemRutter#Reclining-Declining Sundials about lack of references- and was satisfied that Snyder and Brandmaier did verify the fact- however proving it, if the reader hasn't used Linear Algebra is difficult.
*{{cite web|last1=Fennerwick|first1=Armyan|title=, the Netherlands, Revision of Chapter 5 of Sundials by René R.J. Rohr, New York 1996 declining inclined dials part D Declining and Inclined Dials by Mathematics using a new figure|url=http://lester.demon.nl/mywww/rohr/|website=unknown|publisher=user on demon.nl|accessdate=1 May 2015|location=Netherlands|language=English}} is clear about the error.
But this is the url, I don't know where this was originally published so cannot as yet verify notability. Also, before we can use it we need to change the notation to one we are using -the BSS notation. This needs to be proof read very carefully. Further if we are to change the formulae from the ones already included we need to mark them up again in <math>...</math>.
But I was already saying that this section is far too bloated- and a lot of the mathematical working out needs to be culled. Great care is needed achieve the balance between being encyclopedic and becoming a manual for sundial constructors and a chatty pieces that limits the scope to what the authors have seen. On looking for the reference it is clear that DI dials are merely a manifestation of the general sundial equation for planar polar orientated gnomons, and the direct verticals, vertical decliners, horizontal, incliners are special cases derived when one of the parameters has been elininated. Polyhedral dials exhibit many dialfaces all derived from this formula.
As you have requested I will C&P the reference over to the page- and check its notability and accuracy later. Thanks for taking an interest.-- Clem Rutter (talk)18:09, 1 May 2015 (UTC)Reply
@Bammesk::Beautiful illustration, and the device is very important. The Sundial page has many problems as the topic is vast. Sundials were independently invented by all major cultures and yet the article is almost totally Eurocentric- and too long. I am working on a new version that will be very different, so that this page is shorter but directs the reader to other articles for instance Capuchin dialsDiptychsQuadrantsRing dials and I hope Angbuilgu. A lot of the repetition must be cut out - there is a lot to do. I am working in my sandbox User:ClemRutter/sandbox/Sundial when I have time!!!
The WP:MOS is quite clear that the ==See also== section is a list of existing articles that are related. It doesn't state anything about illustrations in that section, but the MOS states that illustrations in an article are not for decoration, they should illustrate a fact within the article. To me that means that an illustration within a section should illustrate a point within that sections. In some poorly developed articles there is a section called gallery- that use the <gallery> markup. In my User:ClemRutter/sandbox/Sundial I have altered the see also to include the new article Angbuilgu that I hope you will write- and in my opinion it will now be correct to include the illustration. In that article, you will probably need to quote the reference I deleted too. I have no knowledge of Sundials within the Korean culture but I hope that I will soon find out. -- Clem Rutter (talk)17:12, 31 May 2015 (UTC)Reply
Clem Rutter, I have no knowledge of Sundials within the Korean culture either. It is not that I mind writing a short article about Angbuilgu or sundials in Korea, I don't mind at all. The problem is that google translation of Korean is horrendous, I mean horrendous!! I am going to look into it and if I find enough material for a couple of paragraphs, in addition to what we have HERE, then I can make an independent short article or a stub. Otherwise I will leave it be. I am not optimistic though, just because of translation quality. Bammesk (talk) 02:22, 2 June 2015 (UTC)Reply
Latest comment: 9 years ago1 comment1 person in discussion
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Latest comment: 8 years ago1 comment1 person in discussion
There has always been a lot of image switching on this page due mainly to good faith enthusiasm. However I don,t think it is helpful to use images that lack a geotag- and we should look to geotagging the helpful images we want to keep, and replacing those that we can,t place. ¬¬¬¬ — Preceding unsigned comment added by ClemRutter (talk • contribs) 23:20, 16 February 2016 (UTC) First edit on a RaspberryPi Epiphany Browser- still looking for the tilde! -- Clem Rutter (talk) 23:25, 16 February 2016 (UTC)
If you're referring to the replacement image I put into the article today, its geographical location is unimportant for its purpose. However, if you look at the image with high magnification, it states that the sundial is in Melbourne, Australia, and, in tiny letters, gives its latitude and "longditude" (sic). I guess that amounts to a geotag. DOwenWilliams (talk) 02:19, 17 February 2016 (UTC)
That prompted it- but then looking at the image below, that has the same problem. So I thought I would flag it up so corrections can be made and we can stem the flow of any future problems. On the Melbourne dial have you noticed there is no noon gap- so potentially they have accuracy problems. — Preceding unsigned comment added by ClemRutter (talk • contribs) 12:33, 17 February 2016 (UTC)
All the Australians I know are too laid-back to worry about a slight inaccuracy in a decorative sundial. :) DOwenWilliams (talk) 15:26, 17 February 2016 (UTC)
Over here we use them to set out computers clocks. Clem Rutter (talk) 17:11, 17 February 2016 (UTC)
Australians?
I got stuck in traffic today, which gave me time to think about noon gaps. The concept is based on the gnomon casting a shadow with two sharp edges, but that would happen only if the sun were a point source of light, which it is not. Its diameter subtends about half a degree, or 1/120 radian, in the sky. Looking at the picture of the Melbourne dial, it seems to me that, seen from the XII hour mark on the dial, the thickness of the gnomon would subtend a similar angle, so at noon the sun would just be obscured, or not quite, by the gnomon. The shadow of the gnomon would be a fuzzy stripe, with maybe a narrow line of umbra in the middle. An observer would see mainly this narrow line, which would be exactly on the XII hour mark at noon. So how would a noon gap work? It would just confuse things. Maybe the Australians were right to omit it. Ditto the makers of the vertical English dial.
DOwenWilliams (talk) 23:06, 17 February 2016 (UTC)
The sun can be considered a point source. but that is not what really matters it is the effect it has on the calculations. But are you sitting comfortably?
The sun is approxiamately 147 million km from each point on the earth- and is a mere 696342 km in diameter, so occupies an angle of 0.00467 radians- or 0 degrees and 16 minutes (approxiamately). Refraction is only likely to occur around dawn and dusk.
The problem comes with doing the dial plate calculations. The angle of each hour is calculated using
dial hour = acttan[sin (L) * tan(15 * t)]
at the extreme end of the range tan produces some rapidly diverging results- and the location of the noon line is essential for accurate plotting.
The alternative is to take a long lunch- starting well before midday. And over lunch we could take some accurate measurements from the dial, and check with the spreadsheet to check that this dial has been correctly set, and is not just a mass produced dial with the town and lat/long post engraved. Clem Rutter (talk) 17:15, 18 February 2016 (UTC)
...note on above edit, I new sectioned this as I was finding it hard to find the subject. Can l blame the pi (Clem my goodness do I need help with my raspberry pi- overwhelmed with ideas but still have not started!!) Hope editors fine with this Edmund Patrick – confer18:28, 18 February 2016 (UTC)Reply
Ummm... You've got confused between the Sun's radius and diameter. Its diameter is twice what you said above, and its angular diameter, seen from Earth, is about 32 arcminutes, or just over half a degree.
Looking at the picture of the Melbourne sundial, I suspect that the thickness of the metal gnomon is something like one millimetre, and the distance from the XII hour mark to the tip of the gnomon is something like ten centimetres. So the thickness of the gnomon would subtend an angle of 0.01 radians when seen from the hour mark, which comes to 34 arcminutes. This angle is very similar to the angular diameter of the Sun (32 arcminutes), so the gnomon might just, or just not, be wide enough to obscure the Sun. Either way, a noon gap wouldn't make much sense.
Latest comment: 8 years ago5 comments3 people in discussion
I have a suspicion that this Melbourne dial was made in Britain or by expat Brits. Many people in the UK mispronounce the word "longitude" as if it had a "d" after the "g". When I was a kid there I thought for a while that having the "d" was correct. I haven't noticed this mistake being made anywhere else in the world, except on this sundial. Therefore, it may well be British.
As a museum worker with a large collection of timepieces I had not come across the D instead of G before but one simple search finds [1]! Is this a whole new field of research, remembering that spelling for hundreds of years was a moveable feast! Edmund Patrick – confer07:54, 19 February 2016 (UTC)Reply
This line of thought could get involved. My first thought was that it could be Grimms Law but that is a red herring. More likely is Velar Consonants before a forward vowelin Early Old English about the 7th century. If you don't nasalise the ng (which is common in Cheshire, Lancashire and Gtr Manchester)- the word Longitude is difficult to say- and commonly we pronounce it with an inserted 'd'- and I tell my ESOL students that is an acceptable work around. Clem Rutter (talk)13:31, 19 February 2016 (UTC)Reply
Edmund's reference shows a D instead of the G, which I had never encountered before. The Melbourne sundial has the G followed by a D. That's how I remember it from my childhood on Merseyside. I have never seen or heard a D in this word here in North America.
I checked the Concise Oxford Dictionary. It doesn't mention any spelling with a D. The only variability it includes is that the G can be pronounced either hard (get) or soft (gem). I find the soft version easier to say. Curiously, the next word in the dictionary, longitudinal, has only the soft pronunciation.
I'm not a spelling fascist. If people want to spell words in unusual ways, that's fine with me, provided the meaning remains clear. I mentioned this matter only because I suspect it gives a clue to the origin of the sundial.
Can anyone tell us if the D is used elsewhere in Britain, or only in northwest England?
Local spellings are not uncommon. Any dictionary will tell you that the plural of LEAF is LEAVES. But here in Toronto many people spell and pronounce it LEAFS. I guess this has to do with the name of the (ice) hockey team, the Toronto Maple Leafs. How the team's name got to be spelled that way I don't know, but literacy and hockey rarely mix
Latest comment: 8 years ago1 comment1 person in discussion
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According to the article & citation the ring dial "was likely invented by William Oughtred around 1600" (currently reference #60, Tuner p.25 ), however the painting The Ambassadors from year 1533 shows what scholar John North (amongst others, cited in the painting article) identifies as a disassembled ring dial as one of the scientific instruments in the painting.
I don't have a specific source that purports an earlier invention of the ring dial, but I think the conflicting analysis (not to mention potential visual evidence) makes it a bit difficult to say Turner's claim is "likely." If it is a ring dial in the picture (I'm unaware that this is in dispute) from seventy-ish years before it was "likely invented", we should probably be less assertive with Turner's analysis. //Blaxthos ( t / c ) 05:10, 1 March 2016 (UTC)Reply
A very valid point worth more investigations. In the wiki page for the painting it is listed as such alongside the polyhedral example, amongst others. Interesting??? Edmund Patrick – confer10:09, 1 March 2016 (UTC)Reply
@Edmund Patrick:Thanks to the Wellcome donation we have many clear illustrations of these portable dials. Compare the unnamed instrument in the Ambassadors with this one. I would love to know exactly what Holbein had found? ClemRutter (talk) 14:44, 18 January 2018 (UTC)Reply
Latest comment: 8 years ago1 comment1 person in discussion
I deleted this section, which read as follows:
"This portable folding German sundial has a string gnomon (pointer), adjustable for accuracy at any latitude. As shadows fall across the sundial, the smaller dials show Italian and Babylonian hours. The dial also indicates the length of the day and the position of the sun in the zodiac."
My reasons:
The text is clearly describing a specific object, rather than pocket sundials in general, and without an accompanying picture it really doesn't convey much useful information.
When the text was orignally inserted, the words "Dorling Kindersley" appeared at the end. Could be a copyvio?
I don't think it's appropriate to place a subsection on portable dials in a section which is basically about how the geometry (mainly the alignment) of dials affects their design, and in fact there's alreasy some relevant information about (presumably) this type of dial elsewhere in the article. 79.73.148.253 (talk) 02:24, 6 August 2016 (UTC)Reply
I think the calls for citations in the Apparent Motion section are a little bit overblown. For example, the linked article on the ecliptic refers to the connections between the ecliptic and the zodiac, and the linked conic section article starts " a conic section (or simply conic) is a curve obtained as the intersection of the surface of a cone with a plane. The three types of conic section are the hyperbola, the parabola, and the ellipse." I suppose though clarifying notes would add some clarity. --Brian Josephson (talk) 11:01, 14 December 2017 (UTC)Reply
Thanks- I agree, if I thought a citation was necessary I would have added it when I wrote the text (I believe I wrote it). In a good faith attempt to improve the article- maybe for a GA, someone added those tags- so we have to address the issue not try and fight the system, and document our reasoning.--ClemRutter (talk) 12:38, 14 December 2017 (UTC)Reply
@ClemRutter: do you have an RS for sundials being unusable because of herds of reindeer? You'd only have to wait for the obscuring reindeer to move, as they do, to be able to read the time. Contrast the situation with a nearby pride of lions, where you would not safely be able to stay around long enough to get a reliable reading of the time.
Latest comment: 6 years ago1 comment1 person in discussion
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Latest comment: 6 years ago2 comments2 people in discussion
During ancient times and the middle ages, people were often more interested in diving the time between sunrise and sunset into 12 hours, than they were in dividing the whole day-night period into 24 equal hours (such uniform-length hours were often mainly of interest to astronomers). This article doesn't even discuss the different definitions of "hour", as far as I can see... AnonMoos (talk) 22:05, 13 April 2018 (UTC)Reply
Because sundials have been around a long time, and many ordinary people in ancient times and the middle ages were often more interested in dividing the interval between sunrise and sunset into hours, rather than in abstract uniform hours (i.e. 1/24 of a full day-night period). Therefore I assume that there probably should be some types of sundials which track the sunrise-to-sunset interval. That was the question that I came to this article to find the answer to, and I was a little surprised to see that it completely avoided the whole issue... AnonMoos (talk) 09:08, 14 April 2018
Latest comment: 3 years ago1 comment1 person in discussion
I know that there are already enough pictures so I won't add this one, but in case anyone wanted a picture of the Greenwich (England) sundial, it is here:
level-4 vital article is rated B-class on Wikipedia's content assessment scale.
An editor has reviewed this edit and fixed any errors that were found.
