Re: Reverse Engineer Oldest SGS
That's pretty neat Gianni. The closest large German city at that latitude is Frankfort. It would be interesting to see if Fer's equations produce the same result. Yes, the equations that Fer and I proposed do yield the same results but, once again, Gianni's method is the best one, because it is easier and more precise to measure lengths than angles (...provided that the equinoctial line is well traced and that the wall is completely vertical!). Grazie mile, signore Ferrari! Anselmo Perez Serrada -
Re: Reverse Engineer Oldest SGS
Fer J. de Vries wrote: Hi John, Assuming the sundial isvertical (because the XII hourline is vertical) and assuming the sundial is well made, just measure two angles in the pattern and it is possible to recalculate the latitude and declination of the dial. The angles you need are the hourlineangles for hour6 and9 for a morning dial or15 and 18 for an afternoon dial. There is a more general formula in case you can't measure these hours. I got it from Soler's book, page 395: Suppose that you have the angle z1 for hour H1 and z2 for hour H2, let's define P = cotg(H1) Q = cotg(H2) p = cotg(z1) q = cotg(z2) A = (p-q) / (P-Q) B = (Pq - pQ) / (P-Q) Then you can get (and check!) the substylar angle from tan(zSS / 2) = 2B / (A^2 + B^2 - 1) and from it tan(LAT) = sqrt( B/tan(zSS) ) sin(DEC) = B/tan(LAT) = sqrt( B*tan(zSS) ) These formulae are complete general so it's worthwhile taking the effort to type them into a spreadsheet. Regards Anselmo
Re: Reverse Engineer Oldest SGS
Hi, Fer: At this moment I do not have at hand Soler's book but you can get the same formulae at Savoie's, page 362. By the way, this chapter about Gnomonical Reposition is just great. Tomorrow I'll call the friend that has now my book and I'll check the equations. I'll try as well to repeat the calculations on a spreadsheet. Regards, Anselmo
Re: OOOPS! Reverse Engineer Oldest SGS
Yes, there was a typo, where you see tan(zSS / 2) = 2B / (A^2 + B^2 - 1) there must be tan(zSS * 2) = 2B / (A^2 + B^2 - 1) Sorry! Anselmo -
Thanks a lot
The Asociacion de Amigos de los Relojes de Sol would like to thank all the people that sent their condolences on the train slaughter in Madrid. Many thanks for your support: we really needed it. As diallists, the only thing we can say is that we shall keep transmiting other people our enthusiasm about a magical invention that an astronomer called Ali Abul Hassan gave us all, no matter if Christian, Muslim or whatever. If you want to send support messages for the victims you can do it in the many websites of Spanish media or as well in our web at [EMAIL PROTECTED] and we'll send them to our Department of the Interior. Thanks again, Anselmo Perez Serrada Asociacion de Amigos de los Relojes de Sol -
DeltaCad and Corel Draw
A friend of mine asked me to make a vertical sundial design that would be captured by Corel Draw (to include decorations, mottoes, and so on). I have never used Corel Draw and would like to know what should and shouldn't do in DeltaCad so that the transfer from it to Corel would be as accurate as possible. I know that if I make a *.dxf file we'll loose the thicknes of the lines but I wouldn't like to loose their vectorizations. Any previous experiences on this or alternate ways (maybe through AutoCad or so)? Best regards -
Re: Mosaic Sundials
By the way, I've learned a lot about making mosaics and it is even easier than making stained glass windows. I encourage more dialists to use this beautiful medium more. You don't need expensive tools or lots of experience to make a mosaic sundial. If you go to the bottom of the Technical Information Page on the SGS website, you will find a description of the two basic mosaic techniques (the poured concrete and the grout methods). Well. I've found in my city a shop that makes laser etching on granite mosaics and some kind of thermical photo-transfer on common ceramic tiles (15*15 cm) from *.jpg pictures or Autocad drawings. I suppose there must be other shops like that in your cities (mine is at www.momentoseimagenes.com). Final results seen quite spectacular, but I do not know if this is suitable for sundialing: for instance, I suspect that the fixing-bath layer that protects the photo-transfer easily degradates with sunlight (the man at the shop says that it'd possibly degradate, but very slowly). As regards to laser etching on granite, it seems suitable, but the kind of granite he uses is rather grayish and it has just an average contrast. Have any of you had any experience with shops like that? Regards, Anselmo Perez Serrada -
Sundial and small birds
Have a glance at a cute and tender picture taken by our associate Antonio Cañones in Murcia (Spain) at http://webs.ono.com/usr023/andanatres/cafeb04.htm Nice, isn't it? Anselmo -
[Fwd: CONXITA BOU on Salvador Dal
I think the sundial painted by Dali in Noon (Barracks Port Lligat) is one that still exists on the wall of a fisherman house, in front of his Home-Museum in *Port Lligat* (not his famous Museum in Figueras). It's told that the sundial was built by Dalí together with the fishermen from the little village. (Picture ref. 1024, 7/1998). In *Cadaqués*, near Port Lligat, where Dalí usually lived, there exist two sundials very similar to the one in Paris, 27, rue Saint Jacques. One can be seen in Curos street, in front of the church (Picture ref. 980) and the other one in Hotel La Residència (Ex-Hotel Miramar) Pl. F. Rahola (Ses herbes). Best regards. Conxita Societat Catalana de Gnomonica [EMAIL PROTECTED] (N 41º41,753' - E 002º14,832') _www.gnomonica.org http://www.gnomonica.org/ _ -
Re: Salvador Dal� , Sundials and Jesu ites
Thanks for your message. Did you see my follow-up posting to the list in which I said I found evidence on the Web that the sundial still existed in 1996? So perhaps it still exists today. -- Richard Yes, I've seen it. But the thing is that I haven't seen it in the neither in the Catalonian Tourist Office Web nor in the Catalonian Sundial Society, except for that picture you posted. This makes me suspect that dial does not exist anymore. Has anybody in the list been to Port Lligat reciently? Regards, Anselmo -
Salvador Dal� , Sundials and Jesuites
which celebrates the 100th anniversary of the birth of Dalí. One of the paintings on display is Noon (Barracks Port Lligat) which Dalí painted in 1954 http://dali.karelia.ru/html/works/1954_07.htm. The painting shows a vertical sundial on the wall of the barracks. Can any of our Spanish colleagues tell us if the building and the sundial still exist? Sorry about the delay, Richard! As far as I've gathered, and waiting for the (more authorized answer) of the Catalan Sundial Society, I haven't found any evidence that this dial is still there. I am afraid it was demolished by those speculative building aberrations commited in the 60's and in the 70's. Are there any other Dalí sundials -- real or painted? Apart from the one looking half face-half shell in Paris, I haven't seen any in one of these books called 'Dali's complete graphical work' I've got at home, but he made so many things and different versions of the same things, that you can't be sure. As regards to the instruments carved in Asia for the Jesuites, most of these instruments must be in the Vatican Museums or in their main 'headquarters' in Rome... I've been told that these are really masterpieces of craftswork, but I haven't seen any of them. Best regards, Anselmo -
Re: Right Ascension
Somewhat off topic, but how do you translate (a) the right ascension of a star and (b) the current date and time into (c) the apparent longitude of the star? - If by longitude you mean the (western) geographical longitude of the star, you may also use the following approximation ( it comes from the nocturlabe equation): GeogLong(Star) = UT - RAsc - 2h*MonthNr - 4h38m where MonthNr equals 1.0 on Jan 1st, 1.5 on Jan 15ht, 2.0 on Feb 1st and so on. Regards, Anselmo Perez Serrada -
Re: On coupled bifilars
As you'll probably know, if we couple on the same device a pair of sundials (of different kinds), not only they show solar time but also the meridian line because the couple is self-orienting. A standard horizontal bifilar dial has exactly the same sheaf of hour lines as a common horizontal dial. Same for a vertical. So it would seem to be no more or less useful for self-orienting. A pair of bifilars on different planes would not be self-orienting. You're right, Chris, but I referred to 'generalized bifilars', that is, having their threads arbitrary curved shapes. Does your statement hold for all these dials as well or could we possibly find three curves in space whose shadows on the ground would make a self-orienting sundial? And if the answer is, as I suspect, 'no', there is still another question: do exist 'projective bifilars'? Is there an equivalent to analemmatics for bifilar gnomons? Dials with significantly different sheaves of hour lines include the Foster-Lambert projection dials. I would suggest pairing two of these, with gnomons at right angles to one another, to get the best sensitivity for orientation purposes. They have the further advantage, over both a common horizontal dial and an analemmatic dial, that the hour lines are independent of the latitude. So, only the gnomon positions and angles need to be adjusted for latitude. Oh, yes, that's what I made for my Seasonal Greetings card at www.relojesdesol.org/NewYear.html They're so simple and beautiful these double Foster-Lambert dials...! Best regards, Anselmo Perez Serrada -
On coupled bifilars
As you'll probably know, if we couple on the same device a pair of sundials (of different kinds), not only they show solar time but also the meridian line because the couple is self-orienting. Do you know under which conditions this also holds for bifilars? I guess that we just need a pair of bifilars not having the same sheaf of hour lines and the couple of them would be self-orienting, even if both are horizontal. I am not so sure what happens if we have a couple of homogeneus bifilars on different planes, but I'd bet they're self-orienting as well. There are a lot of similar questions on this, which seems a promising field in gnomonics. Any comments or suggestions on this? Best regards, Anselmo Perez Serrada -
Seasonal Greetings card from the AARS
The Asociacion de Amigos de los Relojes de Sol wishes you all a happy, healthy and wealthy new (tropic, sidereal and anomalistic) year and invites you to take a glance at our Seasonal Greetings card at http://www.relojesdesol.org/NewYear.html Best wishes, Anselmo Perez Serrada www.relojesdesol.org P.S.: The dial in the foreground is not set to the the Solstice Day, but for my birth day and hour... This is not, of course, a matter of ego; it's just for aesthetical reasons...:-) ! -
Your opinion on Cesare Baj's Kit
I'd like to receive your opinions on Cesare Baj's Meridiane, kit completo per la construzione. It seems interesting but I'd like if it's got something else than an introductory kit, you know: a compass a bubble level, a portractor and a string... Thanks in advance, Anselmo Perez Serrada -
Re: Harold E. Brandmaier?
I'd like to ask you about your book on matricial gnomonics, its prize and how to get it. I use Fer de Vries' matrix algorithm to calculate any planar sundial, and I believe it's a perfect method to implement into computers. I suppose you've extended his method, don't you? and I'd like to see how you did it. By the way, have you tried to do the matrix calculations through quaternions? The calculations are quite cumbersome, but very straightforward and concise. Best regards, Anselmo -
Quadrans novus
Thanks to all the people who helped me find Hal Brandmaier. Now I've got another question :-) Does anybody know what exactly is the Edmund Gunter's quadrans novus? I've read it's some kind of simplified astrolabe, but I haven't seen any other information on it or, better yet, a picture of it. Thanks again, Anselmo Perez Serrada -
Harold E. Brandmaier?
Could anyone please give me the e-mail address of Harold E. Brandmaier? Thanks and sorry for the trouble, Anselmo Perez Serrada -
Re: New Sundial books?
I totally agree with Gianni's remarks on his 'Five Reading Suggestions'. I would add another two italian books: 'L'ombra e il tempo' by Aldo Trinchero and the 'Prontuario Gnomonico' by Fabio Savian. In my opinion Mayalls' book is very good for beginners (better than Waugh's). On the other hand I do not completely agree with Claude: However, it requires a computer! The reason to discuss the use of the hand calculator was because many of NASS beginners do not use computers. Indeed, a common complaint when I was the membership chairman for NASS was about the mathematics involved in most books or articles. First, you don't need a computer to program these formulae: you may use a programmable calculator that may be bought for less than 20 euro and, second, I bet that everyone interested on calculating a sundial is also interested on computers... which can be used in public libraries for free. I do believe that the spreadsheet approach is much simpler and easier for interested beginners but, anyhow, Claude's formulae could be very easy to dump into the computer, so for beginners the difference is more theoretical than practical. Only if (s)he becomes more interested on the topic I'd recommend an strict mathematical+ computer based diet. Best regards, Anselmo -
Re: Sundial bridges
No doubt it is a nice tower but to mention it a sundial is overdone. There is written: /The orientation of the tower means that the shadow of the central needle on the circular platform acts as a (rather impractical) sundial./ It's a vertical needle and an horizontal ring. That could be a horizontal sundial at the pole but Barcelona is in Spain. When I saw the tower at Montjuich I wansn't interested in sundials yet, but I agree with Fer's remark: it isn't a sundial at all. However, J.M. Vallhonrat and his colleagues in Barcelona could possibly tell us more about this interesting non-gnomonic (!?) tower. I still remember when I was in Rotterdam (Nederland) having seen something like that in front of the KPN Telephone Company and reading in a touristic guide that in could also serve as a sundial. After two or three visits there (fantastic place, the Willhemina Plein roundabouts, by the way) I finally called Fer that explained to me that, of course, that thing was not a sundial. So I guess these gnomonical claims are more frequent than we expect. Finally, I have been told that there are more bridges and buildings by Calatrava here in Spain resembling sundials: strictly speaking none of them is a true sundial, but they're nice approximations. Best regards, Anselmo Perez Serrada -
Re: Spanish style sundials
Can anyone point me to suitable styles of dial (probably from the Spanish-speaking world) that would be appropriate to the site, please. John, Take a look at www.relojesdesol.org/Soler.html Regards, Anselmo Perez Serrada -
Corner shadow declination problem by stars
Maybe some of you will remember a rather complete booklet by Gianni Ferrari on how to determine wall azimuths by many methods... like the one of the corner shadow. Well, this method is very simple but not so much accurate as one could imagine. There are two main sources of error or inaccuracy: * The most important one is that one can't determine precisely when the Sun crosses the wall's plane: shadows are fuzzy because of the Sun's finite angular size. * Second you have to consider errors on the wall: certainly walls have bumps, the wall's edge to the ground is unreliable, walls are not completely vertical, and so on. However, you can get a better precision with the same method using a tripod, a small spyglass (or something like this) and a brilliant circumpolar star (or better yet a couple of them like the Big Dipper's pointers). If you know its Right Ascension, and the sidereal time when it crosses your wall's plane you can calculate its declination in the same way. Best regards, Anselmo -
Re: Spanish style sundials
Can anyone point me to suitable styles of dial (probably from the Spanish-speaking world) that would be appropriate to the site, please. Oops, (Sorry, I pressed the Send key before I finished) John, Take a look at www.relojesdesol.org/soler.html There are a lot of 'classical' sundials from Majorica As far as I know, all Jesuitic missions had a sundial, however it was usually made of wood or painted on the wall so I suppose most of them are erased. Here in Valladolid we have a very good set of these dials (carved on three walls) in La Santa Espina monastery, but need urgently be repainted so that they can be seen again. One of these weekends I'll go there and take some pictures I can upload on our web. Regards, Anselmo Perez Serrada -
More on Cardinal Direction Software
Sorry for being so pedantic, but the program doesn't consider the 360 deg Midnight Sun in the Polar Caps, and it'd be very easy to pop up a message reporting about this. Best regards Anselmo Perez Serrada 41.73 N 4.63 W -
Re: Place de la Concorde
I have inserted the pages on Rafael Soler's dials (see http://www.relojesdesol.org/soler.html) the locations of most of the dials, as some of you asked. Dr Soler told me that there are people trying to convince the local authorities to create a Sundial Trail in Majorica, provided that in that touristical island there is one of the biggest densities of sundials in the world. Let's hope they get it! Best regards Anselmo Perez Serrada P.S.: By the way, has anybody in the Eastern Coast taken photos of the sky at night? This must have been the only good thing of the blackout... :-( -
Sundials for children
As I promised, I have uploaded in http://www.relojesdesol.org/Museo/museo.html a brief summary of the activities I made for the workshop on Basic astronomy for children I taught at the Science Museum of Valladolid. I implemented there many of the suggestions you sent (thanks again!) and I believe the children enjoyed all the activities, but some of them weren't properly understood, for instance the one I made to determine the approximate hour counting how many steps long is your shadow... One has to consult a double entry table and it is too cumbersome for the smaller children. On the other hand, the 'dance of the planets' proposed by Sara was a complete success. At the moment the page is written in Spanish only and the pictures are uncomplete (I didn't alwas have somebody at hand to take the picture) and do not have very good quality (I do not want to burden people's computers with huge images of 'me and my friends on our summer holidays'), so I apologize for both things. Oh, and, of course, as somebody warned me, the *only* summer storm we've had in this summer appeared just on the evening we were drawing the analemmatic on the ground, so you not only have to clean the windows or wash the car in order to get rain, you can draw an analemmatic (thank you Mr. Murphy!) as well. Best regards Anselmo Perez Serrada -
Re: Motto T'is nothing but a magic shadow show
And just by sake of curiosity: does anybody have the original arabic quotation written in kufic symbols? Try http://www.okonlife.com/poems/page4.htm Hope this helps... Patrick Thanks Patrick, Dave, Tony and the rest for your contributions to my question on Khayyam's quotation (Terry, if you think your comment is pedantic, then we should rename the Mail-List as Pedantry-and-from-time-to-time-gnomonics, because we are always making remarks of this kind or even worse... and we really enjoy them!). These interested in islamic sundials should visit Esteban Martinez's http://inicia.es/de/RELOJANDALUSI or, much better, visit the Spanish region of Andalucia. Best regards, Anselmo Perez Serrada www.relojesdesol.org -
Motto T'is nothing but a magic shadow show
In our introductory course to gnomonics we are going to give the kids a little diplomma. I thought it could include a motto and I belive the classic by Omar Khayyam would do very well, you know, the one that says T'is nothing but a magic shadow show that explains the heavens. Now the question is: Does anybody have the complete and exact quotation of the motto? And just by sake of curiosity: does anybody have the original arabic quotation written in kufic symbols? (I know that Omar Khayyam was Iranian but, to my knowledge he used to write in arabic, didn't he?) Best regards, Anselmo Perez Serrada -
More on gnomonics and children
A lot of thanks to all who cooperated sending their ideas and/or files for my course on gnomonics for children. I am in debt with you all and, apart from THANKS, the only thing I can say is : Keep sending suggestions! :-)) I had already been thinking of some ideas you sent, but didn't know if they really worked, and some others, like Sarah's Dance of the Planets were really new to me. I am intending as well to make games like If the Earth were a pea and a century was a second... or Find the time with your own hands (based on a couple of Compendium's articles). or Where are we now, Captain? (using a nautical sextant on the mainland). I'll try to finish the short course taking them to the Museum's penthouse and having them show the real constellations to their parents, telling the mythological story of each... but I am not sure if I'll be able to get all the permissions I need to have the museum open afterhours (and if get the cooperation of the clouds as well!). Any previous experience? As regards to Peanuts copyrights, I know nothing about these things, but as far as I can remember, there were many years ago some comic characters like them in Italy a long time before the Peanuts appeared in the USA (you know? Italians have been making art for more than 25 centuries, so they always can say they invented *it* first, no matter what *it* is ;-), so in the end maybe the pictures you saw are not the real ones, but their italian grandparents :-) All my best regards, - Anselmo Perez Serrada www.relojesdesol.org -
On gnomonics and children
I have been asked for giving a short summer course on 'Basic concepts of cosmography' to children aged from 6 to 10 at our Science Museum here in Valladolid. I am supposed to show the children the movements of the Sun, Moon, Planets, the seasons, where and why lies the North, teach them how to recognize the basic constellations, and so on. As the course will be given mainly at daytime I'll tell them about the Sun and, of course, about sundials. The thing is that I have never teached these concepts to so small children and I do not know if they'll be able to understand and learn all the things they need in just three days. Does anybody have any previous experience on this? Do you know about suitable resources (mainly sketches and graphs: I've got thousands of astronomical photos) on Internet? Any suggestion will be welcome. Anselmo Perez Serrada -
Re: Sundials at Pole
Dave Bell wrote: On Fri, 20 Jun 2003, Gianni Ferrari wrote: Some years ago there was a short discussion, on the Italian Sundial Mailing List, on the sundials at the Pole: I try to translate in English [ :-) ] my considerations at the time. I refer to the South Pole and, obviously, to the season in which the Sun is there visible. Gianni Ferrari :-) Wonderful! This was a beautiful treatment of the issues, advantages and disadvantages of dialling at the Poles. A nice reduction to very understandable terms, in the spirit of "Flatland"! First I must say that I fully agree with Dave. Gianni's posting to the list was (once again) fantastic. And second, I do not know you, but from time to time I happen to see in the list things that were on my mind (or even on my notebook) some time before but didn't have the time or the ability to develop. Far from being frustrated at this, I feel comforted because (lazy me!) I do not have to write it then and because usually it is better explained by them than by me. I talk about this because in these stifling heat days in Spain I had been thinking on a story I could write for our bulletin ANALEMA. It was in an embrionary stage and I didn't feel I could write it in English, but I leave here the idea in case somebody wanted to keep further with it. The story begins like that: "And there it was. In a solitary Norwegian cliff, not far from the crowded North Cape toursitc resort, looking at the sea and waiting for somebody whose existence I seriously doubted one early morning (or was it late evening?) of July. [ ... ... .. ]. Then the man [I just met] said --- So you came here to see the Midnight Sun? --- More or less. In fact the weather was so hot in Spain and the ticket not so expensive that I thought 'why not?'. Then somebody told me that this place was much quieter than North Cape and... He interrupted me to say, --- Oh, yes, and the Sun is so wonderfully big here when it bounces on the horizon... --- Well, it's geat indeed, but not bigger. As a matter of fact the Sun is a big smaller when it is close to the horizon, it is just our eyes that cheat... He didn't let me finish again and said, --- My name is Lambert, Foster Lambert, and I believe we had an appointment here. Please follow me. [... ... ... ] When the plane was completely full with the provisions and all kind of tools and materials he had been packing before, he paid to the pilot and urged me to take my place on such crowded plane and happily said 'And now, let's go back home, my sweet North Pole home' [... ... ... ] Little by little, I become convinced of the plane wasn't going to crash against the icy waters, or at least not immediately, and then I began to think about the moment when he paid the pilot and all the packs full of things we had around us. Finally I told him, --- Sorry about this personal question, but how do you earn your living there in the North Pole, because all these things cost money... --- Oh, it's obvious my friend, it's obvious!. I make equatorial and polar dials for all the world. Fully tested and genuine perfect equatorial and polar dials made by Foster Lambert, Ltd. My dials are expensive, I admit it, but they're the only ones that can be properly called these names. He told me about his artisane dials when we got into touch through e-mail but I didn't believe him, because I didn't believe either that he lived in the exact North Pole as he claimed... but then, after six hours travelling northwards on that bizarre plane I was beginning to believe that everything he told me when was true and that I was about to see the most strange dialling workshop in the world. [ ... ... ] " Well, this is it more or less. Suggestions and comments are welcome. Anselmo Perez Serrada
Re: Best Time for Setting Sundials
I've often wondered if there is a best time of day to set a sundial using the Time method (as opposed to the compass, the Polaris, the GPS and plumbob shadow methods). I'm thinking that the best time of day to precisely set and/or read a horizontal sundial would be at mid-morning and mid-afternoon (those times that are halfway between sunrise and apparent noon and apparent noon and sunset). These setting reading times would avoid the early morning and late afternoon affects of maximum atmospheric refraction and would also avoid the compressed hourline markings that are close together at noon which make time estimation more difficult. Does anybody agree with my theory? Is there a best time for setting sundials? You are right. Making a bit of mathematics it can be shown that the highest insensibility to errors is reached when the Sun crosses the prime vertical (ie, the one that contains the East and West points). You can ask a topographer or consult a good astronomy book for more information about this, but your reasoning is much crisper and essentially correct. Best regards, Anselmo Perez Serrada -
Re: Precise EOT Program - Comments and a correction
However, the method of simple differences introduce a 12 hour phase error so we would be better off producing the differential dEOT/dt. As the fourier approximation is linear this can be done with high school calculus. I've included the differential function below. Luckily this produces the same numerical result (to two dec. places) as before except the date is now 23.0UTC Dec (as expected from the phase argument). Beware! The derivative of an approximating function need not be the approximation of the derivative of the real function. Besides, we must take into account that all algorithms to calculate the EoT aren't very robust and are only accurate for a more or less narrow span of time. No algorithm would be able to calculate the EoT on the day when Ramses II was born, for instance. And finally, if John or somebody else wants to work in the range of 10 sec they'll have then to take into account other difficult to calculate factors like the atmospheric reffraction (the formulae we know are all rough approximations). Best regards, Anselmo Perez Serrada -
First year of gnomonica italiana
This on is just to wish a happy first birthday to Gnomonica Italiana, with the hope that the Coordinamento Gnomonico Italiano keep doing such a wonderful bulletin for many years. If you do not know yet Gnomonica Italiana, go and borrow it from your Sundial Society. Even if you do not read a single word of Italian, you'll surely get astonished at their careful design and marvelous pictures... And as regards to the contents, well, there write Gianni Ferrari, Mario Arnaldi, Fabio Savian, Guido Tonello e tutti quanti... so there is nothing more to say. (Beware! You'll probably get green with envy as I did!) Best regards, Anselmo Perez Serrada -
Re: Dial calculation mystery
John Carmichael wrote: Hi Dave: I know you wrote the list asking for answers, not questions. But I don't understand the whole basis of the Britannica instructions. They say: A horizontal dial designed for Chicago's latitude radiates as a 42 deg ellipse. For this example we use a 42 deg ellipse to determine the hour lines' radiation on a horizontal dial at 42 deg latitude. I've never heard of using an ellipse to construct a horizontal dial. Neither Mayall or Waugh use this "ellipse method". And I've never heard of an ellipse being described in terms of "degrees". What in the world is a 42 deg ellipse? John, I think I can help you on this. They use a very elegant method to draw a sundial based on geometrical affinity that traces back to our High School days: 1. Draw two concentrical circles : one of radius r and the other one of radius r*sin(Lat) 2. Now draw a sheaf of 24 equispaced lines from its center as if it were an equatorial dial. 3. These lines intersect the circles at points I' and I'', II' and II'', and so on up to XXIV' and XXIV''. 4. Now trace horizontal lines from the inner points and vertical lines from the outer points. Let's call I the point where the lines from I' and I'' intersect, II the point for II' and II'', and so on. 5. If we connect these points we just have the analemmatic ellipse, right? Well, but if we trace lines from the center to these points we get a horizontal dial for that latitude. Isn't that nice? Maybe somebody more skilled for drawing than me could make a sketch of this smart construction. Best regards, Anselmo
Adezma's book
into retail bookstores, because I didn't rely very much on electronically buying used things (why such great differences in prizes?). Anyway, I'll look carefully the small letter and if I become convinced I'll buy it from them, any advice on this? By the way, Mike, is his snail-mail address the same that comes in the Compendium 5-1 ? In that case, I've got it. Anselmo Anselmo, I have Robert Adzema's address if you want to write to him - he is not on e-mail as far as I know. Contact me directly if you would like it. Mike Shaw 53' 22 North 03' 02 West Wirral, UK [EMAIL PROTECTED] - -
Re: On canonical hours4 and the perils of Popism (!)
Hi all, Well, maybe this time I will reach the end. Now lets go about the office of Terce, Sext, and Non. I am really impressed by your tour-de-force on canonical hours. It is really valuable and full of erudition. I'll read your articles in more detail and then I'll try to translate the 'basic' set of St Benedict's rules in a comprehensive algorithm (if possible) as in Tavernini's program. A lot of thanks for your help. And, by the way, changing a bit the topic: yesterday it was St. Bede's Day and I wondered who is the Gnomonists' Saint Patron, perhaps him? Does anybody know something about this? Best regards, Anselmo Perez Serrada -
Canonical hours and the Art of Love
A lot of thanks for your so complete explanations, they're very interesting. I knew that Canonical Hours were so variable, but I tried to set a trade-off between simplicity and their original definition. However, perhaps I was too optimistic or simplistic and it isn't really possible to implement these hours with a reasonable accuracy in a more or less straightforward way. I'll keep studying your e-mails and other sources on the topic and then I'll decide what to do next. By the way, in our bulletin ANALEMA nr 37 there is an interesting article by MM Valdes on Gouliardic Canonical Hours as described in Ye good love book, a delicious satyrical work made by a Spanish archpriest in the XIVth century in the fashion of Chaucer's Canterbury Tales, so to say. Well, in paragraphs 372 to 387 the book describes canonical hours from Matinae to Completae and explains what gouliards (that is, itinerant monks not adscribed to a monastery and therefore having usually dissipated way of life) did on each of them at the time. Acording to MM Valdes, there is an *implicit* second meaning on each of the tasks he describes, being all of them sexually *explicit*. Fortunately for the decency and good name of this Mailing List, the text is too difficult for me to translate into English without loosing the second meanings, so I'm afraid I have to finish at the most interesting :-D Best regards, Anselmo Perez Serrada -
Re: On canonical hours1
While waiting for Mario Arnaldi's distribution of canonical hours I realized again that in gnomonics *almost* everything has been previously said (but hurrah for the *almost*!). In the 9-3 NASS Compendium there is an article by J.M Valhonrat that describes the different interpretations for canonical hours. I talked as well to my dear Prof. Fernando Munoz Box and explained to me more or less what Mr.Valhonrat says in his article. If I understood well, he disagrees with him at considering canonical hours as instants instead than intervals, but his explanation and distribution of hours is essentially the same and that of Mario. The main problem for my UbiSol program is that night hours (and mainly the three Nocturnum) are not uniquely defined, varying depending on the abbot's interpretation of St. Benedict's Rule, the latitude, etc. But I prefer leaving that explanation for Mario, because he spoke first and also because he knows much more than me about this. Sorry, Mario, about my interrupting you and thanks for your explanation, Anselmo Perez Serrada -
Re: On canonical hours
Dear Anselmo, I write you because I tried your page http://www.relojesdesol.org/UbiSolENG.html and maybe I found that there is some errors. Dear Mario, First of all, a lot of thanks for your attention to my page. I am grateful to you for your help. Now, I changed the coordinates to my own coordinates (Ravenna) 44.41 N, -12.20 E. And I got now legal time correct (h 0.16), but at the same time the program sais the UTC as h. 22.16. I think that it should be h. 23.16, isn't it? And because this error also the local and solar time are wrong. Now, as far as I know, Ravena is at UTC+2 during the summer time, so these calculations are OK. The problem stems on definitions: I follow the Spanish National Observatory's convention that defines the Europe-Central Official Time as UTC+1 always (!) and Legal Time as UTC+1 in winter and UTC+2 in summer. I have seen in other books different definitions, so probably your problem comes from here. At last I'm not agree with the canonical indication, now we are not more in Vesper as it is written, we are in the first Vigilia since three hours. But reading your explanations in your email I may see that your way to subdivide the canonical time, There are also errors in the way they are written. Yes, I've consulted different people and they gave me different definitions of Canonical Hours, so I followed Rafael Soler's criterion which seems dominant in Eastern Spanish and (I supposed, according to U. Eco) in Italy as well. According to this, we have - from sunrise to noon, hours PRIMA to SEXTA - from noon to sunset, hours SEXTA to DUODECIMA - from sunset to midnight, hours VESPERAE and COMPLETAE - from noon to sunrise, hours MATINAE and LAUDES However, I'd be very interested in your distribution of canonical hours. Thanks again for your attention, keep sending suggestions and congratulations for your wonderful designs, Anselmo Perez Serrada, 41.63 N 4.73 W -
On canonical hours
Some people have asked about the last line on UbiSol (http://www.relojesdesol.org/UbiSolENG.html) that shows canonical hours... Well, as you'll probably know, this was a way to approximate temporary hours (very roughly!) by means of vertical southern equi-spaced sundial. As the approximation wasn't very good (medieval monks didn't need much accuracy, either) and as the concept of time in Middle Ages was different from ours, they used intervals rather than exact times, that is, we are at 6th (SEXTA) or 9th (NONA) hour, and Noon happens between 6th and 7th hours, with no additional precision. The algorithm I have used can really give fractions of canonical hours, but that wouldn't be historically correct. That lack of precision was even worse at night: there were only four nocturnal 'hours' linked to four times of prayer: VESPERAE, COMPLETAE, MATINAE and LAUDES. Midnight happened at some instant between COMPLETAE and MATINAE. Finally, if you look through Umberto Eco's The name of the Rose, you'll be able to spot some references to these times and the kind of rituals that were performed at each one of them. As far as I know, Eco's references are correct. Best regards, Anselmo -
Re: Total Eclipse
On Sun, 11 May 2003, John Carmichael wrote: There will be a total lunar eclipse on Thursday, May 10 Eh? May 10 *was* Saturday, Thursday *will be* May 15... Dave - Just to fix things: The eclipse begins at exactly 2003 May 16 01:05 UT, it reaches its maximum at 03:40 UT and finishes at 06:15 UT. Depending on where you are you'd be able to see one or other part of it. For more specifical information you should check your closest observatory's web. Anselmo -
Sun Clock ScreenSaver
Do you remember Joerg Heitkoetter's Java Applets that draw on an Earth's map the actual position of the Sun and the Moon? Our associate Jose Luis Hidalgo Sanchez reports us about the following URL http://www.mapmaker.com/sunclock.asp which contains a FREE downloadable screen saver that shows the same map I told you above. I found it very nice and handy. Best regards, Anselmo Perez Serrada -
Re: UbiSol ibi claritas v 0.1
Gracias por tus felicitaciones y, sobre todo, por recordarme que
tenía por ahí un programilla a medio hacer.
Te envío algo que he encontrado por ahí sobre las efemérides
solares. Acabaré haciendo un artículo sobre ello, pero hasta
entonces creo que con eso te servirá. Infórmame sobre cómo
van los progresos con tu programa.
Un saludo,
Anselmo
back to "Positional
Astronomy""Sun, Moon Earth Applet"
Astronomical Algorithms
The motions of Earth and planets are usually computed in ecliptic
coordinates, based on the plane of the ecliptic. The position of an object
is defined by the ecliptic latitude (=0 for the sun), the ecliptic
longitude, and the distance.
The figure represents the elliptical orbit of a body K, the Sun
situated in the focus S:
We consider a fictitious body K' describing
a circular orbit around S with constant velocity, with the same period as
the real body K, and situated at P' at the
instance when the real body is at the perihelion P. The angle PSK' is
called mean anomaly M, increasing linearly with
time. The problem consists in finding the true anomaly (angle PSK) at a
given instant, when the mean anomaly M and the eccentricity of the ellipse
are known.
Julian Day (valid from
1900/3/1 to 2100/2/28)
Julian day: 86400 s, Julian year: 365.25 d, Julian Century: 36525 d
double JulianDay (int date, int month, int year, double UT){
if (month=2) {month=month+12; year=year-1;}return
(int)(365.25*year) + (int)(30.6001*(month+1)) - 15 + 1720996.5 + date +
UT/24.0;
}
Solar Coordinates
(according to: Jean
Meeus: Astronomical Algorithms), accuracy of 0.01 degree
k = 2*PI/360;
M = 357.52910 + 35999.05030*T - 0.0001559*T*T - 0.0048*T*T*T; //
mean anomaly, degree
L0 = 280.46645 + 36000.76983*T + 0.0003032*T*T; // mean longitude,
degree
DL = (1.914600 - 0.004817*T - 0.14*T*T)*sin(k*M)+ (0.019993 -
0.000101*T)*sin(k*2*M) + 0.000290*sin(k*3*M);
L = L0 + DL; // true longitude, degree
convert ecliptic longitude
L to right ascension RA and declination delta
X = cos(L); Y = cos(eps)*sin(L); Z = sin(eps)*sin(L); R =
Math.sqrt(1.0-Z*Z);
eps = 23.43999; // obliquity of ecliptic
delta = (180/PI)*arctan(Z/R); // in degrees
RA = (24/PI)*arctan(Y/(X+R)); // in hours
compute sidereal time
at Greenwich (according to: Jean Meeus:
Astronomical Algorithms)
T = (JD - 2451545.0 ) / 36525;
theta0 = 280.46061837 + 360.98564736629*(JD-2451545.0) +
0.000387933*T*T - T*T*T/3871.0;
convert tau, delta to horizon
coordinates of the observer (altitude h, azimuth az)
sin h = sin beta sin delta + cos beta
cos delta cos tau
tan az = (- sin tau) / (cos beta tan delta - sin
beta cos tau)
Homeback to
"Positional Astronomy""Sun, Moon Earth
Applet"
Last update: 11/01/2001
Attachment converted: Macintosh HD:anomaly.gif (GIFf/JVWR) (0007D7C1)
On changing coordinates and editing UbiSol
I just took a look at UbiSol for the first time. I noticed that the legal time was 5:25 and the solar time was 12:25. (at default coordinates) This is a huge 7 hour difference. Shouldn't the difference be equal to the Equation of time? Thanks, John, for testing my script. Well, the program takes the local time from your computer but you have to introduce by hand your local coordinates. Click on the link change coordinates and write them on hte blanks. Also, the exact value of the EOT would be a useful addition to the data. Mmmmh The value of the EoT I give is accurate +/- 5 seconds. It is enough for sundialing, and if we wanted more, we'd have to use one of these ad-hoc algorithms that seem taken from Harry Potter's magic book. I'd prefer that users could be able to see in the source code the steps I've followed and eventually improve them. By the way, some users have asked me on how to download the JavaScript file Hhoras.js . These are the steps: 1. In your browser press File - Save. If you are requested to save as well the related *.js and *.css files answer Yes. 2. Now in your computer search and edit the Hhoras.js source code file You can use any text editor you like or any commercial web builider like DreamWeaver. Best regards, Anselmo -
Re: On cookies and English version of UbiSol
So, Anselmo, thanks for your choice of a 'clean' Internet... We are probably all able to change the coordinates each time, and we probably have to, because we want to have the calculations for different places, not necessarily ours... Well, if you're going to run the UbiSolis script offline there is another option: 1. Search and edit the UbiSolENG.html source code file 2. Find the text CHANGE THIS 3. Change the values to these of your place And this is all there is to it! If any further enhancement in this respect would be deemed useful, it could be brought by making provision to store a number of places with corresponding coordinates, and/or leaving the possibility to introduce one's own places... Yes. They've got something like that in the NOAA's web. While I think what to do with (or without) the cookies I'll keep it this way: probably there are more urgent things to improve in UbiSol, aren't there? Best regards, Anselmo -
On cookies and English version of UbiSol
One other thought has occurred to me regarding the setting of new coordinates - if these are stored in a 'cookie' by the JavaScript - the user would not have to set up the calculator each time at their own location A lot of thanks for your help, John. In fact, the idea of the calculator came to my mind when I was making a simple exercise on how to set up JavaScript cookies, but I discarded the idea because I thought it'd be unpolite to introduce cookies in some other people's computers. You know this is a controverted question! Anyway, John's suggestion gave me the idea to introduce the cookies BUT asking first the user for permission. What do you people think about this? By the way. Attending to your requests I've made a full English version of UbiSolis. It is still at http://www.relojesdesol.org/UbiSolENG.html I'll try to make a Dutch version when I've got time for it, and I would greatly appreciate your sending me translations in other languages. Keep sending suggestions! Anselmo Perez Serrada -
Instruments astronomiques
For those of you who are a bit fed up with those webs full of 'fireworks and little men dancing around' here goes a web 100% full of interesting contents: http://www.ens-lyon.fr/RELIE/Cadrans/activpedago/TextesCours/CadresCours/frames.htm (... and as an add-on, it is a good chance to refresh the French we learnt at High School, which is becoming a bit rusty!). Best regards, Anselmo -
Re: UbiSol ibi claritas v 0.1
Hi Anselmo The main version of the calculator on the site looks very good, particularly the three column layout. I also found the Excel spreadsheet very useful for playing about with the algorithms. A lot of thanks, John. It is a pity that the algorithms in Excel seem so abstruse. I've tried to avoid this in the JavaScript, even if that means loosing precision or processing speed. I hope that now everything is much clearer. By the way, did it work properly? What about a Mk 2 version Sorry, but what is that of Mk 2 ? which is kinder to those of us creatures who live South of the Equator and East of Greenwich ;-)) Possibly a set of North/South and East/West buttons in the coordinate pop up window. Yes. I thought about the N/S and E/W controls, but then I discarded them because they could darken the main procedure. I think it is as much difficult for the user to press the 'minus' key than a scroll menu. However, I'll take into account your suggestion, because most of our possible (Spanish Speaking) readers live in the Southern Hemisphere. Just to let all of us dialist's know that we really are not going to see anything further this day - Civil (-6deg.) Nautical (-12deg.) and Astronomical (-18deg.) twilight ;-)) Well, I intend to give the lenght of the three twilights in future versions, but right now I'd prefer to have everything working allright. Best regards and thanks for your attention, Anselmo 41.63 N 4.73 W -
UbiSol ibi claritas v 0.1
I have left in http://www.relojesdesol.org/UbiSol.html a tidied up version of our Solar Ephemeris Calculator. I have included many of your useful suggestions, and I hope it works more or less OK. It lacks many things, but I hope it hasn't got many bugs yet. Like the rest of the web it is written in Spanish, but I believe it can be easily understood. If not, you can download a not so cute English version at http://www.relojesdesol.org/UbiSolENGL.html . Both need the HHoras.js file ; be sure you've downloaded it as well. Best regards, Anselmo -
Re: Bugs on another online solar calendar
I would like to help these of you who helped me find bugs and faults
in my online solar calendar.
I am especially grateful to Gianni Ferrari, Antonio Siccardi, David
Bell, John Hall and Jack Aubert.
A lot of thanks!
I am working on solving the bugs you reported to me and I have to say
that I think I have solved
almost all of them just by doing the following, which can serve as an
advice:
-
DO *NOT* use the JavaScript Date() class except when
absolutely neccessary. It is much better to work with angles
and translate the results into hh:mm:ss format at the end.
-
When I did this all the problems got solved. I am not saying that the
Date() class has got flaws (I leave
this for the gurus), just that it is much safer to work with angles.
I am not completely sure my script always calculates well the Julian
Date (and consequently, the DifferenceOfDates),
and maybe some bugs could stay there but (I cross my fingers) the rest
of them apparently have been solved.
As regards to the vocabulary, I have accepted all your suggestions, but
still I am not sure about Noon...
Is it correct to say 'True Solar Noon'? or just 'True Noon'? I wouldn't
like to use cumbersome expressions
like 'Solar Transit' or so.
And about the superfluous decimal figures (nice but useless) I have
received as many opinions against
them than in favour, so I don't know what to do.
Thanks in advance for your help and, please, keep sending suggestions.
Anselmo
x-html!x-stuff-for-pete base= src= id=0HTML
SCRIPT LANGUAGE=JavaScript
var rad2deg = 180/Math.PI;
var deg2rad = Math.PI/180;
var Latitud = 41.63;
var Longitud = 4.73;
var Tseg = 1000;
var Tmin = 60*1000;
var Thor = 60*60*1000;
var Tdia = 24*60*60*1000;
var miReloj = null;
var VentanaCambiar;
function normaliza(ang) {
var numrevs = ang/360;
return(360*(numrevs - Math.floor(numrevs)));
}
function redondea(num, ndec) {
var mult=1;
for(cnt=1; cnt=ndec; cnt++) mult *= 10;
return Math.round(num*mult) / mult;
}
function HourToString(objDate) {
var horas = objDate.getHours().toString();
var mins = objDate.getMinutes().toString();
var segs = objDate.getSeconds().toString();
if (horas.length == 1) horas = 0 + horas;
if (mins.length == 1) mins = 0 + mins;
if (segs.length == 1) segs = 0 + segs;
return( + horas + : + mins + : + segs + );
}
function DegToHMS(ang) {
ang = normaliza(ang);
var horas = (Math.floor(ang/15)).toString();
var mins = (Math.floor(4*(ang%15))).toString();
var segs = (Math.round((ang*240)%60)).toString();
if (horas.length == 1) horas = 0 + horas;
if (mins.length == 1) mins = 0 + mins;
if (segs.length == 1) segs = 0 + segs;
return( + horas + : + mins + : + segs + );
}
function Parar() {
clearTimeout(miReloj);
}
function actualizar(cerrar) {
// Esta función pasa los valores del formulario de abajo a la ventana
principal
window.document.forms[0].lat.value =
VentanaCambiar.document.forms[0].NuevaLatitud.value;
window.document.forms[0].lon.value =
VentanaCambiar.document.forms[0].NuevaLongitud.value;
if(cerrar==true) VentanaCambiar.close();
}
function Cambia() {
VentanaCambiar = window.open(, Cambio, widht=400, height=120)
var contenido =
'HTML HEAD TITLE CambiarCoordenadas /TITLE /HEAD' +
'BODY BGCOLOR=wheat FORM' +
' Nueva Latitud (N): input name=NuevaLatitud br' +
' Nueva Longitud (W): input name=NuevaLongitud br' +
'input type=button value=Aplicar
onClick=javascript:opener.actualizar(false);' +
'input type=button value=Aceptar
onClick=javascript:opener.actualizar(true);' +
'/FORM BODY' +
'HTML';
VentanaCambiar.document.open();
VentanaCambiar.document.write(contenido);
VentanaCambiar.document.close();
}
// === FUNCION PRINCIPAL ==
function darHora() {
Latitud = document.forms[0].lat.value;
Longitud = document.forms[0].lon.value;
var ahora = new Date();
var huso = ahora.getTimezoneOffset(); // en minutos (de tiempo)
var ahoraUT = new Date(ahora - Tdia + huso*Tmin);
var FechaRef = new Date(2000,0,1,12-huso/60,0); // 1 de enero de 2000 a
las 12:00 UT
var DifFechas = (ahoraUT - FechaRef)/Tdia + 1.0;
var FechaJD = ahora.valueOf()/Tdia + 2440587.5; // ALT: 2451545.0 +
DifFechas.valueOf() + 3/24;
var Hahora= ahora.getHours()*15 + ahora.getMinutes()/4 +
ahora.getSeconds()/240;
var Hhuso = huso/4; // en grados
// = algoritmo de Savoie 53
LM = 280.46+0.9856474*DifFechas;
LM = normaliza(LM);
M = deg2rad*(357.528+0.9856003*DifFechas);
LAMBDA = LM + 1.915*Math.sin(M) + 0.02*Math.sin(2*M);
var Decl = rad2deg*Math.asin(Math.sin(deg2rad*LAMBDA)*0.3977724943);
var AscRec = rad2deg*Math.atan2(Math.sin(deg2rad*LAMBDA) ,
Re: Yet another online solar calendar
A lot of thanks for your exhaustive test of the program. Later I'll answer your comments in a more detailed way. Now just a hint for you and these who wrote complaining that the legal time wasn't right: The clock gives the time of my IPS, which is in Spain (Central Europe Time Zone), but if you download the page to your computer it should give your local time. Sorry, it was my fault not to tell you about this. However I have detected some flaws regarding the getTimezoneOffset() function and with the substraction of Date objects for my JavaScript version. I'll try to fix it as soon as possible. Please keep reporting more bugs or incorrect working (for instance, is it OK at the southern hemisphere?). Anselmo Perez Serrada -
Bugs on another online solar calendar
Hello Anselmo, I have tested the new program to calculate the Sun's data and I have found some not correct things . I list them: - it is not possible to change the date of the day and the time of calculation Yes. This feature will come in future versions. Now I've only tried to make a Solar Clock. - the time is always that of Spain ( I think ?) with a 2h difference from the UT value Some people that had this problem, got it fixed when they downloaded the page and run the script off-line. It does not make much sense because JavaScript runs on the client's side, not on the server's, but it does not make sense either that the script remembers the place where it was created... I'll have to look through this more carefully (ouch! my JavaScript reference warns about possible misbehaviours if one doesn't use the Date() class properly). - the altitude of the Sun is calculated without refraction (?) Yes. I thought that the effect of the altitude over the sea level is more important than that of the refraction,. This is why I didn't introduce it. - the instants of dawn and sunset are calculated or without refraction, or with a very approximate refraction value: the instants differ from those correct of around 4m (for my city). These differences produce errors also in Italic and Babilonic hours I suppose it is essentially the effect of refraction and altitude. Anyway I have just calculated the astronomical crepuscle, not the civil or nautical ones, which in some way would be more correct. - in my opinion it is wrong to give values with a lot of decimal figures if they are not all exact. The altitude of the Sun is, for example, given with 5 decimal figures, that is with a precision of 0.04 arc seconds, while only the refraction gives errors of several arc minutes. I agree with you and I would be a bit ashamed if my pupils should see me doing this. But, you know, I showed the script to a friend of mine with no decimal figures, only integer values, and he asked Why the Sun does not move? Do you mean it is fixed in that position? and I thought it was more 'dramatical', so to say, to include moving numbers like in a countdown: they mean nothing but somehow show the Sun moving. For possible controls you can download the program GEFFEM (in Italian) from our site http://www.gnomonicaitaliana.vialattea.net/software-gnom2.htm Oh, thanks a lot. I didn't know about it. Best regards and thanks again, Anselmo -
Yet another online solar calendar
I have left in http://www.relojesdesol.org/UbiSolENG.html a beta version of what we intend to be (smth. like) the Dialist Companion of the 'Asociacion de Amigos de los Relojes de Sol' but that would probably become into 'yet another online solar calendar'... :-) We've implemented not so accurate algorithms because we would like the users could hack the JavaScript code and customize it to their needs, if they like to. However, the precision is enough for sundialing in dates around the year 2000.0 You are invited to test it and tell us if it doesn't work. I am afraid it has got some hidden flaws, but I am not completely sure if the flaws come from our code or from these strange dwarfs that lurk into navigators; so any comment will be welcome. Best regards, Anselmo Perez Serrada -
Re: frog
Fabio, That dial is so cute!!! It would be great for a playground or outdoor learning center for children. If you liked the frog you'll love to see the rest of 'Fabio's gnomonical amazing creatures' at www.nonvedolora.it Best regards, Anselmo -
Re: camera obscura dials - Diameter of the hole
Congratulazioni Signore Ferrari! Your comments on the hole size are just superb. A lot of thanks for them! Anselmo -
Re: On Meridian dials - camera obscura dials
Thanks you all for your contributions on my request about meridian dials. If you know more (curious or rare ones, for instance) they'll be welcome. By the way, have these dials been built in other temples than Catholic ones? Do you know about Mosques, buddist or other religions themples having meridian lines? And what about civil buildings? As regards to the dimensions of the 'pin'-hole, I haven't found any reliable guideline except that from Fantoni's book: the hole's plane should be perpendicular to the point in the meridian line which is equidistant from both solsticial points. Makbe the discussion we held last year on pinhole cards should cast some light on this topic... Best regards, Anselmo Perez Serrada -
Re: Arc de Triomphe
specially to Gianni Ferrari for his thorough analysis of the question. In middle latitudes we've got +/- 30 deg around the EW line to 'place' our gaps. This is enough to see with a certain frequence alignments like that described by John Carmichael. And I suppose as well this is the reason why many burial monuments and temples from all ages have got EW oriented 'windows'. As this kind of things are so appealing to the public, I am considering including a collection of pictures on this topic in our web, so please, send me more like these by Jean-Paul Cornec. As regards to conical gnomons I must say that they're a gold mine: they've got thousands of nice properties and can be used for everything (azimuthal, babilonical-italian or sidereal hours, shadow-plane sundials, and so on) as you can see in Fabio's web www.nonvedolora.it And, talking about the past, F. Menendez Pidal discovered that the old Spanish village of Castil de Peones (42º28'58''N 3º23'2''W) has got a sundial in his coat of arms (see attachment). We do not know much about heraldics and ignore how, when and why could the sundial arrive there. Any hint? Do you know of any other old sundial-logos? In these tragic days we're living, best wishes for all. Anselmo Perez Serrada Attachment converted: Macintosh HD:CastilDPeones.jpg (JPEG/JVWR) (0006D97C)
A sundial in Mercury
Perhaps you know that there was a project to send a sundial to Mars; the dial was designed (and maybe built, I don't know), but you'll agree with me that the best place to set up a sundial would be Mercury. It's not only its weather (sunny skies with no clouds!) but the fact that the year in Mercury (2111 hours) is almost exactly one and a half mercurian days (1407.5 hours). This, combined with a great eccentricity of the orbit (20.563 %) yields a huge equation of time and a weird movement of the Sun over the mercurian horizon. Finally, the great size of the Sun produces a big pinhole effect over the nodus' shadow. Does anybody know of any attempt to design such challenging dials? Best wishes for the new year, Anselmo Perez Serrada -
Can we see stars by day? (More on ST)
If we want the Local Sideral Time, that tells us from how many hours the Vernal Point is passed at our meridian and what is the Right Ascension of a star that is at the meridian itself, we may use the following formula, that derives from that of Anselmo: Local ST = Time_of_the_clock + TZ - Longitude/15 + 2*NrMonth + 4.64 hours The value 4.64 instead of 4.5 from a better precision. The TZ and the Longitude ar positive if West. Yes, you're right, but I think it's simpler to remember the local corrections for your place, as follows: I know I am at 4.44 deg W, that is, +20 min from Greenwich, so the last term in my formula must be around 5 hours instead of 4.5. I also have to remember that here UT=LegalTime -1 in winter and LegalTime - 2, so for my place Local_ST = LegalTime + 2*NrMonth + 3 or 4 hours Everybody can make the same calculations for their local longitude. If we know the Local Apparenty Time ( the time of a sundial) we have : Local ST = Apparent_Local_Time + TEq_min/60 + 2*NrMonth + 4.64 hours These formulas can be useful, for instance, to draw on a sundial the lines with constant Sideral Time or the line that shaws on the dial when a star or a constellation will pass at the meridian. For example : the line that tells us that in 12 hours the Vernal point will pass at the meridian or that tells that in 8 hours we will have at South the constellation of Scorpio; etc. Oh, yes. For instance, you can draw the line for ST = 6h45m which is the Right Ascension for Sirius, the brightest star on the sky (after the Sun). If you look at the (Southern) meridian when the nodus is on that line you'll be able to see Sirius (even at daytime!) provided that you have a clear sky and good sight (or a pair of binoculars instead). Best regards, Anselmo Perez Serrada -
A rule of thumb for sidereal time
This is probably an off-topic, but I've noticed that many people fond of gnomonics and even of astronomy do not know this simple rule of thumb to calculate the sidereal time (you know, the celestial meridian which lies just above our heads at a certain moment): ST(at Prime Meridian) = UT + 2*NrMonth + 4.5 being NrMonth 1.00 for Jan 1st, 1.50 for Jan 15ht, 3.25 for March 8th, and so on. Some old dials (not only sundials) show this kind of time and most of the people do not know a rough rule to verify them. Addingly, this rule is handy to orientate ourselves in the night sky. Notice that at September-Descending-Libra Equinox ST coincides with UT (more or less). Best regards, Anselmo Perez Serrada -
Aries and the rest
PREI often include Aries and Libra symbols on dials I make. I'm sure it is, or used to be, common practice. David Brown 2.05W 52.75N - Dear fellow dialists, I've also seen these zodiacal signs in many sundials to mark the spaces between date-lines. I do not like this practice because it raises up that (otherwise harmless) superstition of astrology, but it is still there in many dials. Ah, and being more accurate, the Sun goes through *twelve* signs in a year (from EclipticalLongitude = 0h-2h to 22h-24h) but through *thirteen* constellations: the twelve zodiacal appropriately shifted and Ophiuchus (The Snake Hunter). Just look it up in a Sky Atlas! Best regards, Anselmo Perez Serrada -
Re: Back to the equinoxes names
'Dragon's head and tail' (which one is the head and the tail?) The head, Caput Draconis, is the ascending node; the tail, the descending. Ascending... northwards, of course Oh, right, I didn't notice. So you mean the HEAD goes to the North and the TAIL to the South... Gee, listen you all! It was *him* who said this, not me! :-) :-) :-) :-) Anselmo Perez Serrada P.S.: Now seriously, I do not think many people could recognize the constellation Draco in our polluted night sky. -
How do we call the equinoxes?
Don't you think it'd be better to call the equinoxes 'ascending equinoxe' and 'descending equinoxe' instead of 'vernal equinox' and 'autumn equinox'? Do you know if the International Astronomy Union said something about this? Best regards , Anselmo Perez Serrada PS: By the way, I am under a persistent 6-week cloudy sky which covers the Sun all day... please confirm that the Sun is still there :-D -
Re: A New That's Cool Analemmatic
Congratulations; your Table Analemmatic is just splendid, and it is a pity that such a beautiful stone is so difficult to get. this type of sundial. Unbelievably, I could not find a single example anywhere of a mid-sized analemmatic that one could put on a pedestal. I found photos and description of tiny pocket analemmatics and large human size analemmatics, but nothing in between! Well, I have seen pictures of similar sundials made by the well-known italian gnomonist Tonello made of slate. I remember they were very elegant and maybe somebody from the Coordinamento Gnomonico Italiano could provide us more info on this topic. This sundial is also rare because it is the first sundial that incorporates Roger Bailey's now famous Seasonal Markers (Bailey Points I call them). Allow me a small joke (sorry Roger!): If we celebrate Roger's smart idea by means of an eponym... Have you stopped a while to think how many recent contributions should be called after Fer de Vries (dV algorythms, dV dials, dV convenion, etc, etc, etc...)? Give him a few years more and we should rename gnomonics as 'DeVrieslogy'. And by similar reasons, we could call it as well 'Fredsawyers-logy', for instance... :-) :-) :-) Best regards, Anselmo Perez Serrada -
And what about bifilars?
I do not know if bifilar dials are or not an outstanding contributions to sundialing in the XXth century... Among other reasons, because I know the general idea of them (from Scientific American) but not the details. However, as far as I know bifilars were invented in 1922 ... I think that these and the conical sundial are the best ones for a single reason: they are completely classical, ie., they could as well have been discovered in the XVth century or in any other. Best regards, Anselmo -
Re: And what about bifilars?
Anselmo, I gave the start to the discussion about typical twentieth century sundial concepts after remarking that some concepts were missing in the survey of Margaret Stanier in the BSS Bulletin volume 14 (iii) of september 2002. Bifilar dials are not missing in this survey. Willy Leenders Hasselt, Flanders in Belgium Hoi, Willy, My remark wasn't a reproach: t'was only a question :-) I hadn't read Stainer's article and I wanted to express my opinion that bifilars and conical dials are perhaps the best contributions to XXth century sundialing. There was, for instance, one man from the Spanish Sundial Society that improved Freeman's sundial, and we've got, of course the smart Shadow Plane Sundials (thanks Mac and Fer!) but I do not think these dials have as much 'classicness' (so to say) as the other two. Groetjes, Anselmo -
Re: Wall Dec
Let me introduce a couple of comments on Bill Gottesman's formula to calculate the declination of a wall (a lot of thanks Bill and Roger!). Sorry if they are on his original article, but like many members on the list I do not have access to it [1st] We can trace a lot of references to this formula in many classical gnomonics books. In fact his square is a smart kind of 'fake vertical gnomon'. For instance, in pag. 75 of Savoie's La Gnomonique you can see the same formula generalized for any inclination of the wall. By the way, perhaps we could avoid the problem of the double solution by posing it as an arctg(), because most programs include the useful function atan2(x,y). Therefore the formula would be something like: tan(A-D) = sqrt(cos²(h) - sin²(h_eq) ) / sin(h_eq) - D = A - atan2( sin(h_eq) , sqrt(...) ) where h_eq is the 'equivalent altitude' of the sun over the wall, calculated as tan(h_ea) = L(gnom)/L(shad). If am not completely sure that this would always work well, but it's an alternative option [2nd] Yvon Masse describes in his web a wonderful procedure to calculate simultaneusly the inclination and declination of any wall just using a single measure like that by Bill (well, we must measure as well how much the square diverges from the greatest slope line). See the link at the NASS. Ah, and I forgot a small piece of advice: make sure that the square lies perfectly perpendicular to the wall's surface. Otherwise you might introduce an unnaceptable amount of error! Best regards, Anselmo Perez Serrada -
Sundials on the moon
I heard somewhere that Apollo astronauts took a sundial to the Moon. Is this true? What is it like? Does anybody have any picture of it? Best regards, Anselmo -
Re: Diffraction Anti-sundial
I believe the best solution is the CD sundial or 'difraction sundial'. You only need a faulty CD and a transparent sticker to draw the lines of a 'spider dial'. See the Compendium, Nr 3 Sept 1990. It works very well indeed. Anselmo I only have Compendia back to the first Digital version, in 1995(1994?). I know what a spider dial is and looks like, but what was the effect of the CD, other than the pretty diffraction patterns? Possibly, a spider dial with no vertical gnomon? That would work well, for sure! And, since I define AOL throw-aways as faulty from the start, I have plenty of the required dial faces... Dave 37.28N 121.97W - -
Re: Diffraction Anti-sundial
I haven't been able to solve them yet. The real one is the following. Hi, Dave I only have Compendia back to the first Digital version, in 1995(1994?). I know what a spider dial is and looks like, but what was the effect of the CD, other than the pretty diffraction patterns? Possibly, a spider dial with no vertical gnomon? That would work well, for sure! Yes. If you hold a CD in the sunlight you'll see a brilliant diametral straight line pointing towards the Sun. This way you can draw in the CD surface the grid of ANY azimuthal sundial to know the hour. Reversely, if you know the hour and the date you can know the Sun's azimuth and the direction of the true North. From them you can easily calculate the declination of any wall. It's just a simple substraction of angles! Perhaps for these purposes it would be better to use a simple azimuthal sundial (see Helmut's Sonne programme) than a 'spider' or Oughtred sundial, because it is easier to interpolate the dates. Cheers, Anselmo PS.: By the way, what has become of the Abu Dabhi sundial? -
Diffraction Anti-sundial
I believe the best solution is the CD sundial or 'difraction sundial'. You only need a faulty CD and a transparent sticker to draw the lines of a 'spider dial'. See the Compendium, Nr 3 Sept 1990. It works very well indeed. Best regards, Anselmo -
Re: Back again on thick gnomons
Hi Anselmo al, In the dusty corner of a mail folder I found an old message that I still wanted to respond to. From:Anselmo Pérez Serrada [EMAIL PROTECTED] To: Sundial, Mailinglist sundial@rrz.uni-koeln.de Subject: Back again on thick gnomons Date sent: Tue, 12 Feb 2002 15:44:33 +0100 Hi there, (This is a remark I passed to make two weeks ago and then I forgot completely ) On 27th-JAN Rod Heil and Fer de Vries were discussing on the thick-gnomon paradox, ie., the fact that sunrise hours and sunset hours cross on the plate when the gnomon is thick so it is not completely correct that these dials consist on two halves. Do you remember? Well, my remark is as follows: of course Rod and Fer are right and therefore Waugh is wrong in figure 5.4 of his book (page 41). Anyway this is a mistake I have seen in many sundials and maybe it is beause the error on the hour read is neglectible. Anselmo Pérez Serrada I don't understand why Waugh would be wrong in fig. 5.4. He is so smart as to include only hour lines from 6 am to 6 pm, and thereby avoids the common error that was correctly signalled by you, Fer and Rod. Kind regards, Frans == Frans W. Maes 53.1°N, 6.5°E www.biol.rug.nl/maes/sundials/ Hi all, Frans is *almost* right: I mistook the page number and I meant fig. 7.2 (in pag 60) as Mac just pointed out. I sent immediately after that message these right values, but maybe they got lost in the hyperspace. Does anybody in the US know if there are new editions of this book with this error corrected (and the logarithms removed!)? Best regards, Anselmo -
Re: Wall alignments
All the methods you've been discussing to find the declination of a wall assume that the INCLINATION of the wall is exactly 90 deg, which is rarely the case... I measured the inclinations of some buildings in my neigbourhood and saw that most of them had inclinations varying from 89 deg to 91 deg, seldom 90 deg and, from time to time, more. An architect friend of mine explained to me the reasons for not giving that exact value but, in any case, there is no point in imposing an accuracy of +/- 0.5 deg in declination if we have +/- 1 deg in inclination. According to D. Savoie (La gnomonique p 321) in medium latitudes we can expect an error up to 4 min (!) for every degree of deviation. An approximate formula is: Err(H) = Err(D)* [ cos(Lat)*tan(SunDecl)*cos(H) - sin(Lat) ] When I want to deal with exact values for declination and inclination I use the routines at Yvon Masse's web or the program SundialAlign! but probably you'll need to make a wedge to accurately place the dial. Anselmo P. Serrada 41.63 N 4.73 W -
Re: Some ideas for constructing sundials
Congratulations! Your quadrant-sundial generator works OK, and it yields quite an elegant drawing in postscript. This one is an enhanced version of an old kind of altitude sundial. There are lots of variations, but maybe one of the most beautiful is the one built in AD 1568 by Giarolamo della Volpaia. You can see it in the History of Sciences Museum in Fiorenze (Italy): it uses italic and babilonical hours because they're more evenly spaced. This venerable kind of sundials also includes the Capuchin, Clog or Saint Rigaud sundial, the Regiomontanus sundial and many more. You can see the same idea in H. Sonderegger's page: http://webland.lion.cc/vorarlberg/28/sonne.htm As regards to using simple lines (circle arcs or straight lines) as date lines, there are very elegant ideas on this topic but there remains always this double-sided problem: a) For certain latitudes (or wall declinations or times of the day) the hour lines get jammed and it is difficult to tell the difference between them. b) Sometimes it is very difficult to interpolate the lines because there are great and/or highly variable intervals between two consecutive curves. Apart from the Oughtred sundial, I do not know about any of this kind of sundials not having these two drawbacks. But maybe some other members do. Thanks again, Anselmo Perez Serrada 41.73 N 4.63 W -
Re: Amsterdam Sundial
I agree with Thibaud: these dials show local solar time. The day when I was there it was a stifling sunny day in Amsterdam and I can't remember very well if there was any difference between both dials (do you remember Poe's verse Our memories, they were treacherous and sere?). Anyway, I'll be going to Rotterdam in mid August, so if I happen to visit Amsterdam and the day is sunny (which is not very common there), I'll try to take pictures of both dials and then we could discuss it. Best regards, Anselmo Perez Serrada Thibaud Taudin-Chabot wrote: This sundial is indicating local solar time. Therefore you have to take into account 1 hour for the summertime and about 45 minutes for the combination of length correction to the 15° meridian and the equation of time. It is made 1722, so Greenwich etc. was not yet known. Did you also see the smaller sundial that is mounted about 20 meters lower? Thibaud Chabot - Thibaud Taudin-Chabot 52° 18' 19.85 North, 04° 51' 09.45 East, alt. -3.45 m home email: [EMAIL PROTECTED] - -
Re: Low moon
We normally pay attention to the sun, his motion though the skies with the daily and yearly cycles. The moon also merits attention. Have you noticed how low the moon has been recently? Lunar declinations were almost -26 degrees for the last few days. Last nights full moon was almost as low as she goes, almost 2.5 degrees lower than the lowest sun. Here at latitude 51 the maximum altitude was just over 13 degrees. Last night sundials acted as moon dials, giving the correct time if you read PM rather than AM. Roger Bailey Walking Shadow Designs N51 W 115 - Hi all, If my Ephemeris Book does not fail me, this is going to happen again on Aug19, Sep15, Oct13, Nov9 and Dec6 this year but, yes, these minimal declinations only happen in full moon in June and July this year. By the way, does anybody know when is it going to be the next Blue Moon (ie., two full moons in the same month)? As regards to the equivalence between sundials and moondials, I am not very sure but I believe this is going to happen again on Aug23, Sep22, Oct22, Nov21 and Dec27, am I right? Greetings, Anselmo Perez Serrada -
Re: Gaztelainak hitz egiten duzu? (Off topic)
Now I am afraid I'll have to apologize again! My sincere apologizes, Khirman: my ironical e-mail went to this guy in the list, I can't remember his name, that from time to time writes saying that he does not understand gringo (ie., English) and complaints for our not using Castillian Spanish...(!) I thought LtCol Keith was too well mannered with him, and taking advantage of my 'Castillianness' I tried (not very successfully as I see) to show him how ridiculous his proposal was. That is it! The more people can reach our messages, the best for everybody: this is my opinion. Sorry again, Anselmo k_man ayuz wrote: Hello peoples, I'm sorry any trouble that some of you had. LtCol Keith E Brandt wrote something that I couldn't understand. I just curious about the sentences, so I ask someone to translate it for me. And PsykiKidd reply my message with the translation. Is that wrong to me to know what the meaning behind the phrases? Let me know if you think the answer is YES. ..maybe some of the members couldn't understand what we say, but... who cares? - Maybe someone else not care...BUT I care! Sorry a lot, k_man. - Original Message - *From:* [EMAIL PROTECTED] *Sent:* Sunday, July 21, 2002 3:06 AM *To:* sundial@rrz.uni-koeln.de *Subject:* Re: About Sundial Astrolabe I used the altavista translater on that, here's what I got: If you speak only Castilian, so that fixed you your question in English? ALONE I SPEAKCASTILIAN THE GRINGO (FOREIGNER) DOES NOT GO TO ME I guess that doesn't make much more sense than the spanish! Troy In a message dated 7/20/02 1:59:01 PM Eastern Daylight Time, [EMAIL PROTECTED] writes: Hi, Thanks for the recommended web site. I appreciate that. Thank you. K_mæñ. can you translate it for me?: ¿Si usted habla solamente castellano, por que usted fijo su pregunta en ingles? SOLO HABLO CASTELLANO EL GRINGO NO ME VA Get more from the Web. FREE MSN Explorer download : http://explorer.msn.com -
Gaztelainak hitz egiten duzu? (Off topic)
Would you mind dumping this message into Spanish to CabraLoca, best know as PsykoKidd, who can't read a single word of English? I do not know where you come from, but I really appreciate :-0 your enthusiastic (?) defense of our language. As a true-blue Castillian (I live 500 meters away from the exact center of the Old Kingdom of Castilla y Leon) I can't help suggesting you to actively support the broadcasting of our language across the internet not by attaching ridiculous messages into a mail list but, for instance, building webs as good as that of the NASS or Sundials on the Internet or Analemma.com, and so on... This way your efforts would be more fruitful and many only-Spanish speaking people could reach these contents and would be very grateful to PsychoKidd, 'The champion against evilish English-speaking surfers'. Ah, by the way, in order to not to hurt your eyes with this pathetical 'gringo-babble' I propose using basque, the most remote ancestor of Castillian, as the official language of the Sundials Mail List (see the Subject line): maybe some of the members couldn't understand what we say, but... who cares? Sincerely yours ;-) Anselmo Pérez Serrada 41.63 N 4.73 W -
Ooops! Sorry PsykoKidd!
not to PsykoKidd... I do not know wy, but I thought they were the same person. My apologizes to PsykoKidd, who indeed is another victim of 'zealous Josuishs'. Anselmo -
Re: Shortest day and latest sunrise
Regarding the attempt to learn why the latest sunrise and sunsets don't fall on the solstices, I think analemma.com has a pretty good explanation. I suppose some background info and lingo is necessary to understand any subject, and that site does a good job of giving the background for the beginners. - Yes, it's really fantastic! -
Re: Keeping it simple
I believe that the simplified explanation of these concepts is very important. Complex scientific overloading, however accurate, can easily intimidate the casual user of one of our creations, to the point of actually making them give up or lose interest in understanding the concept at all. Not everyone, obviously, is looking for that level of information. An elegant, simple explanation for some of these basic concepts - the ones they must confront in order to understand and use the dial they are standing in front of - is what is needed to welcome the uninitiated to the concept, and for that matter, to dialing as a whole. I too am trying to figure out how to explain these things, and I hope that by doing so I might even increase our ranks by sparing my customers the initial intimidation of the subject matter. If the mountain does not look too steep more people may be inclined to climb it, so to speak. I wonder what the party definitions would be to some of these basic dialling concepts, such as EoT? Jim, I agree 150% with you! It is very important not to make things more complicate than they are... Sometimes it is the lingo, some others the tools (mathematical, theoretical, academical) we use to describe them and some others our own limitations to express them... And unfortunately many people gets discouraged from knowing more about someting beautiful, useful or simply' mind-expanding' (so as to call it) because of this. As an accidental teacher, I tend to think a lot about which are the foundations, the barebones, of what I am going to teach: which is the core and which is just chatter. And I can't help thinking that maybe it is our fault that most people are so'scientifically and technically illiterate'... even my own engeneering colleagues! Best regards, Anselmo -
Shortest day and latest sunrise
A friend of mine asked me the following question: According to the popular proverbs, the erliest sunset happens in Dec-08th and the latest sunrise in Jan-03th but, as we all know, the shortest day of the year is Dec-21st (in summer it happens the same)... I checked the dates and they seem to be correct, but when I tried to find an explanation on this I found long documents dealing on equations of time, analemmae, sidereal times and lots of things I don't understand. Can you give me an easier explanation in plain language? Then I tried to explain him this curious fact by saying Imagine you could see the Earth from the Sun: then, the Earth spins around itself not every 24h00m but every 23h56m, blah, blah, blah As the Earth's axis is tilted towards the North Star, you do not see perfect halves of the Parallel Circles, but sometimes more and some others less than this, blah, blah, blah . I'm afraid I wasn't quite successful and I still wonder if there is a better way to explain these things to common people, maybe by drawing circles in a bowl as Fer de Vries did or some other way. Any suggestion? Anselmo Perez Serrada -
Testing our web
I am testing a minimal-preliminary-not-yet-official web page for the Spanish Sundial Society. At the moment you can find it (mind you, written only in Spanish) at www.telefonica.net/web/centrogrial/AARS.htm Please, those interested in it tell me if you can see it well, if the links work properly, if you find any mistakes or lacks, etc. I warn you that I belong to the 'keep clean the internet of rubbish'-league :-) so I haven't included anything you can easily find somewhere else. Cheers, Anselmo Perez Serrada -
On shadow sharpeners (again!)
Hi dialists! Wouldn't it be better using these extra-cheap binoculars instead of a pin-holed card as a shadow-sharpener? I got one of them for free when I bought a book (no kidding!) and they cast a sharp image of the Sun when focused on a white piece of paper (you can make a cardboard shield to improve the contrast). The image is better than that of a pinhole (maybe it's an artifact, but I think you can even see the specks on the Sun's surface) and the only drawback is that I'm not sure if the lenses introduce some distortion into the true position of the Sun. Any help on this? Cheers, Anselmo -
Message for Spanish speaking sundial 'aficionados'
deals on gnomonics webs written in Spanish, and I didn't find any other better way to reach those people interested in them than this list: == Hola a todos: 1. Habéis visto la revista electrónica de gnomónica Carpe Diem? Echad un vistazo a http://es.geocities.com/soliombra/ porque creo que el proyecto merece la pena. 2. Esta otra es para los socios de la Asociación de Amigos de los Relojes de Sol: no os parece lamentable que no tengamos una simple página web que nos dé a conocer? Yo estoy elaborando una muy sencillita que cuenta lo más básico de la Asociación. Si os parece, le doy el retoque final y os la envío un día de estos. Si os gustase (aunque sólo sea como una 'versión en construcción') podríamos publicarla en alguno de estos sitios de 'free-hosting' (por cierto, ¿Conocéis alguno digno?). 3. Y esta es para quienes no sean socios de la AARS y deseen serlo: pues eso, que os pongáis en contacto con los que organizan todo esto... Tenemos la ventaja de poseer una lengua muy extendida y seguro que en Venezuela, Chile, México, Perú, etc. tenéis un montón de cosas interesantes que contar. Daos cuenta de que si no se le puso el adjetivo 'Española' a la Asociación es a propósito: la AARS está abierta a todos quienes deseen enviar sus colaboraciones en lengua castellana, española o como os guste llamarla. Un saludo Anselmo Pérez Serrada 41.63 N 4.73 W -
On shadow sharpeners
First of all, thanks for all your kind responses on shadow sharpeners. Now some comments on them: [Edley] The simplest of these is a simple pinhole placed far enough from the dial surface to focus the image of the gnomon on the surface. Yes, I knew about these. In Spanish we call them 'disco perforado' and in French I think it is 'oeilleton'. My book tells (as a rule of thumb) that its diameter must be around 2.5% of its distance to the wall. Is that correct? [Edley] Other more complex shadow sharpeners are disks inside circles or slits in a complex gnomon. There are several articles on these in the NASS compendiums. I could clip a few out and send them to you as pdf files if you like. Yes, please, send me these pdf files. I'd like to know more about them and, in general, about the physical principles which they are based in. [Mac] What's needed is for someone to assemble the information from all those postings into a fairly brief, but accurate explanation of how to use and understand shadow sharpeners. Even after all that been posted on shadow sharpeners, some of us just learned some important new things about them. Mac, thanks for being more straightforward than me, because that was EXACTLY what I was subreptitiously asking for ;-) You know, I was afraid of getting an answer like That's gorgeous, Anselmo, why don't you do it yourself and post it to the list? :-DDD This property of the 'parallel plane === round shadow' keeps being quite surprising to me. [Patrick] The ones we have recently been talking about - and the ones we discussed in May 1999 (it's a common toopic on the sundial mail list!) I know, and I apologize for being redundant. I lost all my e-mail from last month due to a trojans attack. (by the way, does anybody know how to get rid of this addiction to the Sundial List? Does the World Health Organization know about this place? :-D) [Mac] If you search the sundial list archives, you will find lots of previous messages about shadow sharpeners. Go to the NASS website (http://sundials.org) A lot of thanks, Mac, I was about to send you all an e-mail asking for these files I couldn't save! Best regards, Anselmo -
How do rotate vertical clocks?
Please, let me be a little bit pedantic... ;-)) Sundialists know well the shadow of the gnomon of the vertical type sundial on the wall rotates anticlockwise. Well, this is true only if the wall's declination is lower than +/- 90 deg. If the wall looks, so to say, NorthEast or NorthWest the hours rotate clockwise. You'll probably get an hiatus, but the sense of rotation is clockwise. Of course this is not the reason why clockmakers chose that rotation convenion: in Rohr's book we can see that, as Mike said, it was probably due to the fact that first sundials were rather astronomical instruments than clocks and they were more or less similar to an spherical sector (its name was scaphe) where the shadow of a needle moved from left to right, ie, clockwise. And, by the way, I think I heard somewhere in the Discovery Channel that aboriginals in Chile knew about rudimentary sundials wich rotated, obviously, Southern-clockwise ;), that is, from right to left. Does anybody know something about this or similar (maybe in New Zealand or in SouthAfrica?) Cheers, Anselmo -
Re: Kitt Peak Sundial Proposal Approved!
Keep us informed on how things are going on and please, place photos of this sundial's evolution on your web. -
On equivalent planes
Thanks a lot for your remarks on generalizing the equations for an oblique plane. As a general rule, any plane being oblique (ie, inclining and declining) where you are is an horizontal one somewhere else. But where? OK. You can consult Rohr's book or derive'em by yourself (it's pretty easy), and you'll get that the 'equivalent latitude' is given by sin(LatEq) = cos(z)*sin(Lat)-sin(z)*cos(Lat)*cos(D) and the 'equivalent longitude' is LongitudeEq = Longitude + arctan( -sin(D) / (sin(Lat)*cos(D)+cos(Lat)/tan(z)) ) being 'z' the zenithal distance of the plane (what you usually call 'inclination' in English, but not in Spanish and French because it can be misleading, etc, etc, bla, bla, bla) and 'D' is its azimuth. Now you have to be careful because the hour angle of the Sun in that place is shifted an angle given by the increase of longitude and the substyle line does not coincide with the greatest slope one, being the angle between them equal to: SD = arctan(sin(D) / (cos(z)*cos(D)+sin(z)*tan(Lat)) ) Ah, and don't forget to carefully look at the sunrise and sunset times over the plane and over the horizon! These are the classical formulae that perhaps everybody in the list know, but maybe somebody didn't have all together. Personally I prefer to use Fer's matricial method which is not so straightforward but much crisper and suitable for computers. Eventually, we have to be VERY careful when computing the inverse trigonometrical functions, because we can get scrambled results. This is a general problem in gnomonics which requires a deeper explanation in some other day. Cheers, Anselmo -
Back from the shadows
Well, here am I again, after three successive virus attacks, a hardware failure (carpets and CD units are incompatible told me the guy at the shop!) and a lot of work kept me isolated from the outer world. I'm trying to recover my e-mail folders from a post-mortem backup, so I do not know what has been going on in the list, but as far as I remember, some of you asked me for the formulae for an analemmatic sundial having its (moveable) gnomon inclined. There they go (copied from Savoie 's book): Let's consider a set of ortogonal axis centered in the foot of the gnomon and pointing towards the East (x), North (y) and Zenith (z). Let be as well i the angle from the vertical line to the gnomon (i = 0 means a vertical gnomon, and i=90 an horizontal one), and D its gnomonical declination (D=0 means a gnomon pointing to the South, D=90 is pointing to the West and so on). The coordinates of the ellipse of hours are: x = -r*(tan(i)*sin(D)*cos(Lat)*cos(HourAng) - sin(HourAng)) y = -r*cos(HourAng)*(tan(i)*cos(D)*cos(Lat)-sin(Lat)) where r is a free parameter (it stands for the radius of the equatorial circle from which the dial derives). And the scale of dates is still a straight segment whose coordinates are: X = r*tan(i)*sin(D)*sin(Lat)*tan(SunDecl) Y = r*tan(SunDecl)*(tan(i)*cos(D)*sin(Lat)+cos(Lat)) From them you can derive all the projection sundials like Foster-Lambert's, Parent,'s, and a lot of curious new ones. Sorry about the delay! -
Inclining declining gnomon alemmatics
Hi dialists! I have translated into English my pedestrians only ;-) spreadsheet that I sketched to calculate and draw the lines for a declininginclining analemmatic dial.As I didn't derive them by myself but copied them from La Gnomonique by Denis Savoie, I was playing a bit with them to see if they worked well and saw that, contrary to what I supposed, the scale of dates sometimes has got an S-like shape. For those of you who are interested in this Excel spreadsheet (please do not expect something like Helmut Roger's!), please send me an e-mail to [EMAIL PROTECTED] and I'll send it to you as an attachment. Cheers, Anselmo Perez Serrada [ 41º 39' N 13º 15' E (from the Hierro island) ] -
On the Hierro meridian line
Hi, John Anselmo Perez Serrada [ 41º 39' N 13º 15' E (from the Hierro island) ] I note that you are a true traditionalist when quoting latitude. Exactly where on El Hierro island was (is ;-)) the zero meridian ? Oh, no! It was a small irony. The other day I saw a French encyclopaedia (written in the 50's!) that used in some maps the Meridian of Paris as a reference and I thought 'Why not bringing to life our old Hierro Meridian?'. This was a widespread reference used since Ptolemy and mainly in the Renaissance times. The Hierro Island is the most western of the Canary Islands and it is supposed that the aforementioned Meridian passed by its most western 'tip', ie., the Punta Orchilla Cape, at about 18 deg 17 min East from Greenwich (excusez moi, je ne sais pas combien des degres depuis Paris! :-). Anyway, until the XVth Century it was quite a remote place only inhabited by a few aboriginals, so I believe there were many Hierro Meridians depending on the cartographers that made the charts. And finally, as far as I've been told, it is now a very beautiful place, immensely quiet and 100% environmental respecting, so there are a lot of reasons for visiting it on holidays. Best regards, [ 41.63 N 4.73 W] Best regards John D Hall Launceston - Tasmania 41.24S 147.07E Mailto:[EMAIL PROTECTED] - -
Re: Inclined gnomon alemmatics
Dave, sorry if I hadn't been clear enough! From where is 'z' measured? Is it 0 degrees when it lies on the ground and pointed North (in the northern hemisphere)? It can be defined in several (equivalent) ways, but the easiest is measuring it anticlockwise from the northern semiaxis to the gnomon. Its value must be then between 0 deg and 180 deg (z 90 deg implies a gnomon leaning southwards) What is the sign/direction of 'd'? Thanks for this one, Dave! I forgot to say that the gnomon must be contained in the meridian (NS) plane, ie., its gnomonic declination should be 0 deg or 180 deg). So the positive direction of 'd' is towards the South. You can derive as well the equations for a declining gnomon, but then they become a bit messy and there isn't much different with the former case: only that the date scale is crossed along the horizontal plane. (you may consult Savoie's book for more info on this topic: his explanation is not as crisp as that by Bruno Ernst but he gives the full equations). If I've got time, I'll try to draw an sketch. Best regards, Anselmo Perez Serrada [ 41º 39' N 13º 15' E (from the Hierro island) ] -
Re: Sloping Analemmatics
Hi all, First of all, my congratulations to Helmut and Roger for the spreadsheet... and for releasing it as freeware in these mean ;-) times where everything is under patent laws. Now, I would even dare to make a small suggestion for next versions: why not including inclined gnomons in order to create Foster-Lambert or Parent Dials or any other arbitrarily inclined projection dial, like the one that John asked about? I sketched it in a rudimentary spreadsheet and it is very easy. Concerning this topic, I strongly recommend you all the article on Projection Sundials written by Bruno Ernst, which you can find in Fer de Vries' web. It's just fan-tas-tic! Greetings, Anselmo - Original Message - From: John Carmichael [EMAIL PROTECTED] To: Sundial List sundial@rrz.uni-koeln.de Cc: Frans W. MAES [EMAIL PROTECTED] Sent: Monday, April 15, 2002 6:15 PM Subject: Sloping Analemmatics Hi All: I have a question. I use the Delta Cad macros to design analemmatics. These macros only permit the design of analemmatics that have flat horizontal faces. But I need to design an analemmatic that is painted on cement that slopes slightly to the south. Let's say the angle of slope is 3 degrees from horizontal and the latitude of the sundial is at 32.5 N.degrees. I thinking that if imput into the DC macro a false latitude of 32.5* - 3* = 31.5 degrees that it would produce the correct drawing for the sloping sundial. Is my thinking correct on this? Thanks anyone John John L. Carmichael Jr. Sundial Sculptures 925 E. Foothills Dr. Tucson Arizona 85718 USA Tel: 520-696-1709 Email: [EMAIL PROTECTED] Website: http://www.sundialsculptures.com - -
Can you contact Roger Bailey?
I still can't send messages to Roger Bailey... Roger, did you solve your problems with your e-mail or maybe is it me? Frank (and the rest of the people), were you able to contacthim? Anselmo Perez Serrada
Re: failed message
Yes I did, but I gave up trying to contact him Sorry, RT - Original Message - From: Frank Evans [EMAIL PROTECTED] To: sundial@rrz.uni-koeln.de Sent: Wednesday, April 03, 2002 8:46 PM Subject: failed message Alas despite several attempts I have been unable to reach R T Bailey ([EMAIL PROTECTED]) although his messages come through in this direction. I wanted to thank him for the thoughtful reply he sent concerning the way old sundialists laid out wall dials using the pole star. Has anyone else had trouble reaching him? Frank -- Frank Evans - -
Viutruvius or Oughtred (2)?
Hi Bill, hi John, hi diallists, First of all, for those of you who hadn't seen it yet I recommend Bill Thayer's page on Vitruvius. It is carefully made and very well translated. And second, thanks John for your comments. Now, the paragraph I referred to is as follows: 8. Other kinds of winter-dials are made, which are called Anaporica. They are constructed as follows. With the aid of the analemma the hours are marked by brazen rods on their face, beginning from the centre, whereon circles are drawn, shewing the limits of the months. Behind these rods a wheel is placed, on which are measured and painted the heavens and the zodiac with the figures of the twelve celestial signs, by drawing lines from the centre, which mark the greater and smaller spaces of each sign. On the back part of the middle of the wheel is fixed a revolving axis, round which a pliable brass chain is coiled, at one of whose ends a phellos or tympanum hangs, which is raised by the water, and at the other end a counterpoise of sand equal to the weight of the phellos. 9. Thus as the phellos ascends by the action of the water, the counterpoise of sand descends and turns the axis, as does that the wheel, whose rotation causes at times the greater part of the circle of the zodiac to be in motion, and at other times the smaller; thus adjusting the hours to the seasons. Moreover in the sign of each month are as many holes as there are days in it, and the index which in dials is generally a representation of the sun, shews the spaces of the hours; and whilst passing from one hole to another, it completes the period of the month. 10. Wherefore, as the sun passing through the signs, lengthens and shortens the days and hours, so the index of the dial, entering by the points opposite the centre round which the wheel turns, by its daily motions, sometimes in greater, at other times in less periods, will pass through the limits of the months and days. The management of the water, and its equable flow, is thus regulated. It is clear thatVitruvius is more interested in reproducing the movement of the Sun by mechanical means than in telling the time and that's why his dial is implemented in a different way than that ofOughtred. But, in my opinion, there is the full idea of the Ougthred dial: making a sundial using the ortographical projection (ie., that of an astrolabe) instead of the classical gnomonical projection. What do you think of it? Happy Easter, Anselmo Perez Serrada
Vitruvius or Oughtred?
Hi dialists! Following the principle that states that ''one way or another you always end up in the classics'' I have borrowed from the public library ''De Architectura'' by Vitruvius in order to read the Ninth Book that deals about sundials. The problem is that I only could get a version translated into Old French, and my pace of reading is veeery slow. Now, therecame I across the description of something that appears to be an Oughtred (or spider) sundial which he calls ''Anaphoric Dial''. Am I wrong or are they basically the same thing? Cheers, Anselmo Perez Serrada
