RE: Time Exhibition
Well done Mike for acting on a nondial. I went to the Time Exhibition a Greenwich a few months ago and had mixed feelings. Please ignore the rest of this message if you don't want my personal reaction! It has apparently been done with no expense spared but I felt missed out on some of the most basic essentials of an exhibition - at least I go to an exhibition to see objects, which I know is a bit unfashionable in the museum design world these days. There were indeed many absolutely first rate, world class, important objects to see and it was wonderful to have a chance to look at them gathered together in London. However a lot of them in the sundial and horological categories are finely engraved brass etcetera and are best seen under a good light - without risk to them. Arranging them therefore in cases with (very interesting) manuscripts and the like which need near darkness for preservation means you can't see the metal things properly. The descriptive labels in the cases seem to be placed neither in numerical order nor in physical order corresponding to the objects. So having seen the small grey number next to something you can't find the dimly lit relevant label. If you happen to be carrying the erudite catalogue, containing some fine essays, things aren't improved because it doesn't appear to have numbers corresponding to those on the objects so you can't look them up in that either, and some very fine and little-known things - where you can't go away and read about them in a standard book - just get an almost footnote mention and little proper description. When you have found the description it sometimes tells you about the interesting things on the back of the object - for example a cubical sundial - but then have the designers condescended to mar their nice grey showcases with anything as useful as a mirror behind it so you can see for yourself? It's still worth a visit - and you can make up your own mind whether I'm just having a prejudiced rant! There are lots of good exhibits on aspects other than time measurement as Mike listed. Perhaps I'll go again in the next six weeks ... Andrew James N 51 04 W 01 18
Re: [britishsundialsociety] Re: head nodus
Dear Patrick, > Yes that's right but I think that John has abandoned his idea of an > analemmatic dial in favour of this suggestion of a conventional horizontal > dial but one without a gnomon. Instead of a gnomon he would use a human > standing at the correct spot for his height. This person's head would > therefore form a nodus whose shadow would fall on hourlines drawn from the > dial's origin. > I only know of one such dial in the UK but there may be more in the US. You made us curious. Where is that dial to be found? Regards, Frans = Frans W. Maes Peize, The Netherlands 53.1 N, 6.5 E www.biol.rug.nl/maes/ =
Sculptural presence of analemmatic dial
Picking up the thread on the analemmatic dial discussion a while back, I think Sara Schechner was quite right in noting: "What these dials lack (often) is a sculptural presence. They are defined by a flat environment, which while attractive and inviting up close, is typically unrecognizable or invisible from a distance. In this regard, people are not drawn up to them. They work best when the spatial environment has some vertical feature to draw the eye in." There is namely no need to limit the hour points of the anal. dial to stones hidden in the grass, or (brass) numbers inlaid into the pavement. The shadow of the (human) gnomon forms a vertical plane, and so the hour point can be any vertical mark or mark on a vertical object. This principle has been applied to the anal. dial in the Genk Sundial Park by RenÈ A picture is attached. Also, the uplifting of the date line in the anal. dial in Leoben (Austria): http://www.tirol.com/sundial/a_3500.htm is based on the same principle. One advantage, mentioned in the discussion, is the vandal- proofness of the anal. dial. Depending on the budget, it should be quite possible to devise an eye-catching analemmatic dial, I think. Dr. Frans W. Maes Dept. of Animal Physiology University of Groningen P.O. Box 14Tel. : +31-50-3632357 9750 AA Haren Fax : +31-50-3635205 The NetherlandsE-mail: [EMAIL PROTECTED] Visit my homepage at: http://www.biol.rug.nl/maes/
Re: head nodus
Hi Patrick: Your idea of a wall to receive the morning and afternoon shadows is a great solution to the problem. But I will have to give it careful consideration if I use it or not because of the additional expense and effort. (Also, vandals love to paint walls). This dial will have the typical "bow tie" shape of a vertical nodus horizontal dial. The decision must be made on where to terminate the drawing of the dial face on its eastern and western edges. One critical factor in determining the size of the face is the "fuzzy factor" of shadows. In previous threads we have discussed that no point on the dial face should be much farther than 100 times the width of a spherical nodus; otherwise the shadow becomes too indistinct and fuzzy. If a person's head nodus measures about 8 inches in diameter, then the maximum distance from head to dial face cannot exceed( 8 x 100)/12=67 feet. Does this look correct to you? John >Message text written by John Carmichael > >>This means that the shadow of the head nodus will reach infinity at >sunrise and >sunset. These dials can not tell time in the early morning and late >afternoon because the shadow is too long. I'll have place a size limit on >the dial face. > >Patrick, have I interpreted this correctly?< > >Yes, exactly so. > >Now I'm not sure of this next bit without doing the maths (sorry you call >it 'math' - singular - in the US, don't you? Another of the tiny >differences in our common language!!). > >If you were to build a circular wall around the dialplate then the shadow >of the observer's head as it came off the dial plate would go up the wall. >This was a common practice with meridian lines in European churches in the >17th & 18th Centuries. In the case here the shadow would never rise up >above the observer's height and you would thus be able to accommodate hours >that otherwise would cause the shadow to stretch out to infinity. > >I believe I am right to say that in such a situation the shadow of any >point on the gnomon of a horizontal dial would fall along the hour line or >along such a line on a vertical wall as described. Each of these >'extended' hour lines on the vertical wall would actually be at an angle to >the horizontal - something close to the angle of latitude but varying for >each hour. > >This needs some further thought if you were to be interested, but if you >have a circular - or any other shape for that matter - horizontal dial to >hand you might like to tape a strip of paper around its circumference to >make a sort of vertical wall and sight along the gnomon to mark on the >strip the 'extensions' of the hour lines. For any particular hour these >will be the same for any 'angle of sunlight'. Give it a go and see what >you think. > >I suspect that this would also work if the wall wasn't circular but I'd >have to think about that. > >It's possible that such a wall round the dial would give visual interest >too - though it might be too expensive to construct one to a height to >accommodate all adults but you might be able to do it for children... >Though to be fair I suppose you wouldn't need this 'wall' for hours other >than those which bracket sunrise and sunset throughout the year... > >If one constructed such a dial it might be easier to mark out these line >extensions by trial rather than by calculation - rather as one often does >for a ceiling dial!! > >It was just a thought anyway. [You have to know when to stop thinking in >dialling!! Just say if you don't want to be confused by these added >thoughts by a Limey who won't even have to build this dial! :-)] > >Patrick > >
Sundials at New Globe
Hello All, My wife and I recently visited the new Globe theater in London. During the guided tour, I spotted a pair of vertical sundial installed on a corner of a brick wall. One dial faced slightly west of south, the other slightly north of west. The two bronze data plates below the dials gave some [not completely accurate] information about the dials, but didn't say who designed, fabricated, or installed them. I'd be happy to learn more details about these dials. Alas, I didn't have my camera with me--imagine, a tourist without a camera! Does anyone know where a picture might be found? Best wishes, Mac Oglesby
Re: head nodus
Hello John, This thread just gets more and more intriguing! It'll be fascinating to see the end result. IMHO, you'd be well advised to make scale models to 'proof out' your designs. For example, fuzziness of the nodus shadow is likely to be a relatively minor factor affecting accuracy--much more important is likely to be the inability of the nodus to be at the correct location, since children (of all ages) don't stand straight, or still, or even at the proper footprint. One reason why most analemmatic dials have hour points only is due to the unpredictable behavior of the human gnomon. If you like the appearance, by all means place quarter-hour lines on your 'human horizontal dial' for aesthetic reasons, but don't expect a sundial with a human gnomon or nodus to give very accurate time. Good luck, Mac Oglesby P.S. And think about exactly what do you consider to be the nodus. The center of the human's head? Or what? Hi Patrick: Your idea of a wall to receive the morning and afternoon shadows is a great solution to the problem. But I will have to give it careful consideration if I use it or not because of the additional expense and effort. (Also, vandals love to paint walls). This dial will have the typical "bow tie" shape of a vertical nodus horizontal dial. The decision must be made on where to terminate the drawing of the dial face on its eastern and western edges. One critical factor in determining the size of the face is the "fuzzy factor" of shadows. In previous threads we have discussed that no point on the dial face should be much farther than 100 times the width of a spherical nodus; otherwise the shadow becomes too indistinct and fuzzy. If a person's head nodus measures about 8 inches in diameter, then the maximum distance from head to dial face cannot exceed( 8 x 100)/12=67 feet. Does this look correct to you? John >Message text written by John Carmichael > >>This means that the shadow of the head nodus will reach infinity at >sunrise and >sunset. These dials can not tell time in the early morning and late >afternoon because the shadow is too long. I'll have place a size limit on >the dial face. > >Patrick, have I interpreted this correctly?< > >Yes, exactly so. > >Now I'm not sure of this next bit without doing the maths (sorry you call >it 'math' - singular - in the US, don't you? Another of the tiny >differences in our common language!!). > >If you were to build a circular wall around the dialplate then the shadow >of the observer's head as it came off the dial plate would go up the wall. >This was a common practice with meridian lines in European churches in the >17th & 18th Centuries. In the case here the shadow would never rise up >above the observer's height and you would thus be able to accommodate hours >that otherwise would cause the shadow to stretch out to infinity. > >I believe I am right to say that in such a situation the shadow of any >point on the gnomon of a horizontal dial would fall along the hour line or >along such a line on a vertical wall as described. Each of these >'extended' hour lines on the vertical wall would actually be at an angle to >the horizontal - something close to the angle of latitude but varying for >each hour. > >This needs some further thought if you were to be interested, but if you >have a circular - or any other shape for that matter - horizontal dial to >hand you might like to tape a strip of paper around its circumference to >make a sort of vertical wall and sight along the gnomon to mark on the >strip the 'extensions' of the hour lines. For any particular hour these >will be the same for any 'angle of sunlight'. Give it a go and see what >you think. > >I suspect that this would also work if the wall wasn't circular but I'd >have to think about that. > >It's possible that such a wall round the dial would give visual interest >too - though it might be too expensive to construct one to a height to >accommodate all adults but you might be able to do it for children... >Though to be fair I suppose you wouldn't need this 'wall' for hours other >than those which bracket sunrise and sunset throughout the year... > >If one constructed such a dial it might be easier to mark out these line >extensions by trial rather than by calculation - rather as one often does >for a ceiling dial!! > >It was just a thought anyway. [You have to know when to stop thinking in >dialling!! Just say if you don't want to be confused by these added >thoughts by a Limey who won't even have to build this dial! :-)] > >Patrick > >
Re: head nodus
I have been asked where the UK dial designed as a gnomon-less horizontal dial was located. In truth I don't yet know. I only found out in talking recently to a UK BSS member who told me inpassing that he had designed such a dial. I expect to receive a report form for the BSS Register in due course. I hope to be able to pass on more details shortly. Patrick
Time Exhibition
Yesterday, I went to an exhibition entitled "The Story of Time", held in the Queen's House at the National Maritime Museum, Greenwich, London. The exhibition covers:- The Creation of Time The Measurement of Time (excellent display of sundials and clocks) The Depiction of Time The Experience of Time The End of Time It is well worth a visit if you can get there, it is on until 24th September 2000 Information I understand, on (though I haven't looked) www.nmm.ac.uk ...and you can walk outside and see Chris Daniel's Dolphin dial ...and get free entry into the Old Greenwich Observatory As is the case with exhibitions these days, you can not get out without passing through the shop. They were selling, at high price, a "Non-Sundial" The gnomon was aligned along the axis of rotation, but so was the dial plate. So it was like a polar dial, but the dial plate was circular, and marked out like a clock face (12 at the top, 6 at the bottom). You will be pleased to know that I sought out the shop manager, and pointed out his obligations under the UK Trades Descriptions Act, and suggested that Greenwich, the home of time, was hardly the place to be selling such rubbish. I wonder if he will remove the offending object. Subsequent visitors may like to check. JPG available on request Mike [EMAIL PROTECTED] 53.37N 3.02W Wirral, UK
Re: Sculptural presence of analemmatic dial
Frans W. MAES contributed: > >Picking up the thread on the analemmatic dial discussion a while >back, I think Sara Schechner was quite right in noting: > >"What these dials lack (often) is a sculptural presence. They are >defined by a flat environment, which while attractive and inviting up >close, is typically unrecognizable or invisible from a distance. In >this regard, people are not drawn up to them. They work best >when the spatial environment has some vertical feature to draw the >eye in." It can also be an advantage where a sundial is required but any vertical feature would conflict with an existing structure. I was recently asked to design a dial which was 'vandal proof' incorporating an international logo. No details of the intended location were given. As you can imagine a 'vandal proof' specification led to a somewhat massive proposal. English Heritage quite rightly responded with "There's no way you're putting THAT in front of XX" So now they will have an analemmatic instead, probably with bronze medallions deep-set in York stone, and everyone is happy. Tony Moss
