Re: How does this sundial function?
hi, probably is not in the intentions of the author but the arcs have a gnomonics meaning. The arcs are in the planes obtained by revolving the horizon plane around the horizontal South-North axis till the plane is vertical. There are seven arcs and they seem to be separated 15° on this rotation. When the shadow of an arc overlaps the 12 hour line it shows an approximation of the temporary hours called vertical hours (from the Ptolemy definition of this angle). The temporary hours start from sunrise to sunset and divide the period into twelve hours. In old times it could happen that temporary hours sundials were built with vertical hours probably because the realization was easier. We don't know if the constructors chose to made vertical hours instead of the temporary hours because it was easier and the error is neglectable or if someone made these sundials without knowing the difference or if the vertical hours were a different ancient hour system. Anyway some ancient temporary sundials show vertical hours. The vertical hours divide the daylight arc in twelve hours like the temporary ones but they haven't a costant length and the difference with the temporary hours increase with the latitude and the declination of the Sun (from negative values to the positive ones). I should be very surprised if the author built a 'multistyle vertical hours sundial', anyway it shows the vertical hour system from the sixth hour to the twelfth. ciao Fabio Fabio Savian fabio.sav...@nonvedolora.it Paderno Dugnano, Milan, Italy 45° 34' 10'' N 9° 10' 9'' E GMT +1 (DST +2) - Original Message - From: John Carmichael To: sund...@rrz.uni-koeln.de Sent: Thursday, October 08, 2009 7:28 PM Subject: RE: How does this sundial function? I think I just figured it out. There is small piece of sheet metal in the shape of a star with a hole in it that is attached to one of the hoops. It projects a beam of light onto the ground. So this must be an aperature nodus. The hoops are just ornamental (and confusing!) From: sundial-boun...@uni-koeln.de [mailto:sundial-boun...@uni-koeln.de] On Behalf Of John Carmichael Sent: Thursday, October 08, 2009 10:03 AM To: sund...@rrz.uni-koeln.de Subject: How does this sundial function? Can any of you figure out how this strange sundial functions? It is called "Sun Shell". It is located at 15151 E. Alameda Parkway at the Aurora Municipal Center in Aurora Colorado USA. It was made by an artist named Rafe Ropek. But who deliniated it I wonder? It is not in the NASS Registry. Here are three excellent photos of it: http://www.flickr.com/photos/7593...@n07/3804098283/sizes/l/in/photostream/ http://www.flickr.com/photos/7593...@n07/3804912094/sizes/l/in/photostream/ http://www.flickr.com/photos/7593...@n07/3804913154/sizes/l/in/photostream/ thx John -- --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: How does this sundial function?
Hi John, It is about 3:30 pm on the dial. It is a "point" dial. On one of the photos you see a schadow of a sun with a hole to produce a spot of light. The hours to use the dial are limited. Best wishes, Fer. Fer J. de Vries De Zonnewijzerkring http://www.de-zonnewijzerkring.nl Molens http://www.collsemolen.dse.nl Eindhoven, Netherlands lat. 51:30 N long. 5:30 E - Original Message - From: John Carmichael To: sund...@rrz.uni-koeln.de Sent: Thursday, October 08, 2009 7:03 PM Subject: How does this sundial function? Can any of you figure out how this strange sundial functions? It is called "Sun Shell". It is located at 15151 E. Alameda Parkway at the Aurora Municipal Center in Aurora Colorado USA. It was made by an artist named Rafe Ropek. But who deliniated it I wonder? It is not in the NASS Registry. Here are three excellent photos of it: http://www.flickr.com/photos/7593...@n07/3804098283/sizes/l/in/photostream/ http://www.flickr.com/photos/7593...@n07/3804912094/sizes/l/in/photostream/ http://www.flickr.com/photos/7593...@n07/3804913154/sizes/l/in/photostream/ thx John -- --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: How does this sundial function?
John, I found a website: www.ropek.net which shows the piece in more detail with an explanation. It shows the lines on the floor to be hourlines. In that case, it would appear that the arches aren't noting the sun's path, but are facing west instead. The top arch has an indicator at the top which crosses the hourlines. I take it that you've only seen it by pictures, too. I did see a link to email the artist on one website, but not his email address. sasch From: jlcarmich...@comcast.net To: sund...@rrz.uni-koeln.de Subject: How does this sundial function? Date: Thu, 8 Oct 2009 10:03:15 -0700 Can any of you figure out how this strange sundial functions? It is called “Sun Shell”. It is located at 15151 E. Alameda Parkway at the Aurora Municipal Center in Aurora Colorado USA. It was made by an artist named Rafe Ropek. But who deliniated it I wonder? It is not in the NASS Registry. Here are three excellent photos of it: http://www.flickr.com/photos/7593...@n07/3804098283/sizes/l/in/photostream/ http://www.flickr.com/photos/7593...@n07/3804912094/sizes/l/in/photostream/ http://www.flickr.com/photos/7593...@n07/3804913154/sizes/l/in/photostream/ thx John _ Hotmail: Trusted email with Microsoft’s powerful SPAM protection. http://clk.atdmt.com/GBL/go/177141664/direct/01/--- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: How does this sundial function?
I think I just figured it out. There is small piece of sheet metal in the shape of a star with a hole in it that is attached to one of the hoops. It projects a beam of light onto the ground. So this must be an aperature nodus. The hoops are just ornamental (and confusing!) From: sundial-boun...@uni-koeln.de [mailto:sundial-boun...@uni-koeln.de] On Behalf Of John Carmichael Sent: Thursday, October 08, 2009 10:03 AM To: sund...@rrz.uni-koeln.de Subject: How does this sundial function? Can any of you figure out how this strange sundial functions? It is called "Sun Shell". It is located at 15151 E. Alameda Parkway at the Aurora Municipal Center in Aurora Colorado USA. It was made by an artist named Rafe Ropek. But who deliniated it I wonder? It is not in the NASS Registry. Here are three excellent photos of it: http://www.flickr.com/photos/7593...@n07/3804098283/sizes/l/in/photostream/ http://www.flickr.com/photos/7593...@n07/3804912094/sizes/l/in/photostream/ http://www.flickr.com/photos/7593...@n07/3804913154/sizes/l/in/photostream/ thx John --- https://lists.uni-koeln.de/mailman/listinfo/sundial
How does this sundial function?
Can any of you figure out how this strange sundial functions? It is called "Sun Shell". It is located at 15151 E. Alameda Parkway at the Aurora Municipal Center in Aurora Colorado USA. It was made by an artist named Rafe Ropek. But who deliniated it I wonder? It is not in the NASS Registry. Here are three excellent photos of it: http://www.flickr.com/photos/7593...@n07/3804098283/sizes/l/in/photostream/ http://www.flickr.com/photos/7593...@n07/3804912094/sizes/l/in/photostream/ http://www.flickr.com/photos/7593...@n07/3804913154/sizes/l/in/photostream/ thx John --- https://lists.uni-koeln.de/mailman/listinfo/sundial
