Hi Thibaud, Because there are datelines on the dial it is possible to draw ananalemmas around the hourlines to correct for EoT. Or use two dialplates with half the analemma for each half of the year.
But it was asked to construct the EoT corretion in the gnomon and to keep straight hourlines and I think that's not possible with the wire gnomon of Bits. For each day the complete wire is used because it is built with infinite "hourgnomons". For a specific day you may correct the wire for the EoT of that day but for the next day you need to construct another wire. It's a daily job to change the wire and that's too much for a simple gnomonist. Best wishes, Fer. Fer J. de Vries mailto:[EMAIL PROTECTED] http://www.iae.nl/users/ferdv/ Eindhoven, Netherlands lat. 51:30 N long. 5:30 E ----- Original Message ----- From: "Thibaud Taudin-Chabot" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Wednesday, January 08, 2003 8:51 PM Subject: Re: Quest for a civil time polar sundial, continued... > Hi Mac and other readers of this continuing story... > > That was a good thought to prepare that resume on the web, I could read it > in peace. > It gave me some thinking and I put down my thoughts so other people might > come to new ideas. > > A polar dial which reads civil time and constructed with one dial/style is > not possible because the datescale on sundial is in fact a declination > scale. For each declination there are two dates involved so there are two > different timeequation values involved. John stated already no analemmas, > so it has to be a single line for two different corrections. Sorry, I think > that is indeed not possible. > But.... why not make two polar dials, each with a different pattern. One > for the summer/autumn and one for the winter/spring. > It might even be the same polar dial with interchangeable > gnomon/style/shadowwire. > Take the dial constructed by W. Bits: each our line can be shifted with the > longitude correction and a slight additional shift for the timeequation. Do > this for summer/autumn. Then calculate bachwards how the wire should be in > winter/spring. If these two different two wires are used in the correct > period the polar dial should read civiltime, or make two polar dials with > fixed wires. > Anybody who thinks this might be possible? > > Thibaud Chabot > > > At 16:08 07-01-2003 -0500, you wrote: > >7 Jan 03 > >Hello Friends, > > > >On December 29 I mistakenly sent to the entire sundial mailing list a > >message intended for one member, Dave Bell. In that message I asked Dave > >if he would be willing to post some materials I had collected concerning > >the problem of finding a shaped gnomon to give civil time directly on a > >polar dial. > > > >Due to a misunderstanding on my part, I announced that such a gnomon had > >been designed about 20 years ago. Alas, we still are looking for a > >solution. If you have any interest in seeing a report on our search so > >far, point your browser at > > > >http://advanceassociates.com/Sundials/A_Civil-Time_Polar_Dial/ > > > >or, for slow typists > > > >http://tinyurl.com/46ss > > > > > >Dave Bell has provided the space, and has taken the time and trouble to > >set up the webpage. I greatly appreciate his assistance with this web > >posting. But any errors are my responsibility, so contact me if you find > >mistakes. General comments are also welcome. > > > >I wish to thank John Close for raising the question, to thank all those > >who contributed to the material posted, and I extend a special thank you > >to my good friend Fer de Vries for providing the quoted text. > > > >Best wishes, > > > >Mac Oglesby > > > >P.S. Please let the sundial list members know if any of you have other > >information to share concerning this problem. > > > >- > > --------------------------------------------------------------------- > Thibaud Taudin-Chabot > 52° 18' 19.85" North, 04° 51' 09.45" East, alt. -4.50 m > home email: [EMAIL PROTECTED] > > > - > -
