I understand the concept that solar time is correct time and I understand the feeling that solar time is the only correct time.
However, from a practical standpoint, a sundial is only a lovely ornament if you miss an appointment because you insist it is 40 minutes earlier than your doctor say it is. What I want to do is make a beautiful, accurate piece of art that is useful and accurate as well as being as true to the ancient arts as possible. But, the reality is, we must live in the world and that means living by arbitrary standard times. That also means that every place has a slightly different sundial design to show the correct time. As incorrect as that may seem, as un natural as many would argue, it is a fact of life just as are death and taxes. In the US, time zones are approximated on certain longitudes but they also follow certain political lines. They roughly follow straight vertical lines but the actual places are the lines of counties. In my case, I live in Hamilton County Tennessee. The next when you cross the county line to the West, you are in Central time. So, if generally follows the longitude as far as the large picture of the entire country. but, if you drew and perfectly vertical line from pole to pole, the line would not be perfectly accurate because of the political lines of county boundaries. Karon Adams Accredited Jewelry Professional (GIA) You can send a free Rosary to a soldier! www.facebook.com/MilitaryRosary www.YellowRibbonRosaries.com From: fer de vries [mailto:[email protected]] Sent: Wednesday, July 27, 2011 9:36 AM To: [email protected]; 'Donald Christensen'; [email protected] Subject: Re: Longitudinal shift? Karon, Your question: Where, within a time zone in the US, is the Solar time correct To me solartime is Local Solartime and that is independant from the time zones. It is always correct. And Willy Leenders loves it. It is the natural time with noon always at 12. (Have in mind that 1 hour solartime is not always of equal length. Our hours from the clock are always equal but solartime is not. Therefore we need to know about the equation of time but that is another discussion.) On the internet I foud for Chattanooga standard timezone -5 hours, relative to Greenwich. So the standard meridian for your timezone is 5 x 15 = 75 degrees West. Chattanooga is about at 85 degrees West so you are about 10 degrees West of your standard meridian. That is 40 minutes in time. This is more then the theoretical borders of a time zone. These theoretical bordes are + 7.5 and - 7.5 degrees of the timezone meridian. But in practice the timezone borders are choosen different. (Most political reasons?) They don't follow straight meridian lines on our maps. Try to find a timezone map on the internet. During Daylight Saving Time your "standard" meridian is 60 degrees and you are 10 + 15 = 25 degrees West of your standard" meridian. That is 1 hour and 40 minutes. Willy read in your mail that you rotated the sundial pattern itself. That is not correct. You should rotate the construction hourcircle with hourlines 15 degees apart with the appropriate longitude offset. I recommand to take look at the website of De Zonnewijzerkring. (The Sundial Society of The Netherlands.) Addres below. The site is in English as well. You may find several helpfull articles there. E.g.: Article of the month Archives 2005 Month 05-09, septmber. There you will find a costruction of a combination of three dials: horizontal, equatoral and vertical. If you rotate the equatorial pattern with hourlines of 15 degrees apart according to the longitude offset you directly can see how the hourlines on a horizontal or vertical dial will change. ( They don't rotate al together.) 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: karon <mailto:[email protected]> To: 'Donald Christensen' <mailto:[email protected]> ; [email protected] Sent: Wednesday, July 27, 2011 1:33 PM Subject: RE: Longitudinal shift? That sounds like what I did. I live in Chattanooga. That is 85 degrees longitude. So, 10 degrees off the median. So, I shifted the dial by 10 degrees and it worked! I figured it out by looking at Shadows. (thanks again, BTW for that program!!) with construction lines in I looked at the dial made normally, then, I looked at it with the longitude correction. It took about two seconds to see what the program had done. Then it was just finding out by how much I needed to change it. So, now I have another question. Where, within a time zone in the US, is the Solar time correct? Is it at the front of the time zone or the center? If the entire zone is 15 degrees, I would never want to offset 10 degrees if the prime is in the middle. But, if it is in the front, that works. Karon Adams Accredited Jewelry Professional (GIA) You can send a free Rosary to a soldier! www.facebook.com/MilitaryRosary www.YellowRibbonRosaries.com From: Donald Christensen [mailto:[email protected]] Sent: Tuesday, July 26, 2011 10:04 PM To: [email protected] Subject: Re: Longitudinal shift? Karon You may be right. I'm not sure what you're asking I'll tell you what I do. I'm in Brisbane australia. Our prime meridian is 150 The town I live in is 147. Therefore my longitude correction is 3 degrees Donald On Tue, Jul 26, 2011 at 11:43 PM, karon <[email protected]> wrote: Do I have this correct? In order to correct for longitude, you determine the degrees from the prime meridian of your time zone. Then, offset the 15 degree hour angle from the center of the top circle. Your first angle is offset from that to mark noon at equinox, then, the rest of your angles are marked at 15 degrees from that mark in both directions, creating non marks on the equinox all the way across. >From there, you simply move back to marking your lines from the noon equinox mark to the CBA point and these are your hour lines. Do I have this correct? Karon Adams Accredited Jewelry Professional (GIA) You can send a free Rosary to a soldier! www.facebook.com/MilitaryRosary www.YellowRibbonRosaries.com <http://www.yellowribbonrosaries.com/> --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial -- Cheers Donald 0423 102 090 This e-mail is privileged and confidential. If you are not the intended recipient please delete the message and notify the sender. Un-authorized use of this email is subject to penalty of law. So there! _____ --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
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