Hello Brent, Thad and all, It is even simpler than this. You don't need a pipe, just a point, the tip of a stick, a disc, with a hole, whatever. The original sundials used this projection of a point principle. The Greek and Roman designs had the point projected onto a hollowed out hemisphere. This was a projection of the sky above through the point giving the shadow on the lines in the bowl.
There are many programs available to do the calculations. My standby is Fer de Vries program for sundial design, ZW 2000. This is based on projections from a point onto a plane. You can include the equation of time correction and have the hour lines in the analemma shape, You can set it for your longitude and correct for daylight savings time. Click here to download the program. http://www.de-zonnewijzerkring.nl/eng/vlakke-zonw-download-zw2000.htm . Fer describes his technique in the paper "Uniform Method to Compute Sundials usable all over the world" available at: http://www.de-zonnewijzerkring.nl/eng/index-vlakke-zonw.htm Regards, Roger Bailey Walking Shadow Designs www.walkingshadow.info "Life's but a Walking Shadow....." From: Thaddeus Weakley Sent: Wednesday, April 08, 2009 3:34 PM To: [email protected] ; [email protected] Subject: Re: The perfect sundial? Hi Brent, No, you are not crazy. Particularily with modern-day computers, you could lay out a very detailed plate showing the time of the light exiting the pipe and hitting the plate. You could even have the equation of time, longitude, daylight savings time, et al all accounted for and calculated into the layout to have such a dial show the local clock time. While there is a little bit of variation with the four-year leap-year cycle that would still show that could only be accounted for with charts or computer, most modern-day clocks aren't set any more-accurately than within a few minutes. At University I was impressed when the clocks were the correct hour.... You could write a program or spreadsheet that would allow you to readily do a different plate or paper print out for any location. The sun will appear to be in many of same places multiple times a year. As the days go from the Winter to Summer extremes, they're mirrored in length and sun positions with days as the days go back from the Summer to Winter extremes. So it seems that the user will still need to know at least which month or Season they are in when reading the dial. The biggest challenge with your dial though may be to design a plate that is simple enough to readily read by the novice to make it easier to read than other sundials. I, and I'm sure others here look forward to seeing this. Good Luck! Thad Weakley 43.3N 73.3W --- On Wed, 4/8/09, Brent <[email protected]> wrote: From: Brent <[email protected]> Subject: The perfect sundial? To: [email protected] Date: Wednesday, April 8, 2009, 5:49 PM Hello; Existing Sundials are pretty much worthless in the modern world with modern clocks. The best sundials, which give the most accurate time are only usable by the experts. I admit I am a novice but I have an idea. The sun is at a unique position in the sky, every minute, every hour, every day, every month of the year. Thus: I propose to make a sundial with a long pipe that has a fixed pivot which can be aimed at the sun and the bright spot that exits the pipe can show the exact time every day of the year projected on an engraved face piece. Are my assumptions correct and am I crazy to think I can make such a thing? Thank you; brent --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial -------------------------------------------------------------------------------- --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.0.238 / Virus Database: 270.11.47/2047 - Release Date: 04/08/09 05:53:00
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