I believe that I am correct in saying that my Wenger Sundial is an analemmic sundial but others may not agree. I have an analemma at each hour. To read the dial one establishes the subsolar point via a pointer and its shadow. This establishes the declination of the sun. One then interpolates between two adjacent analemmas using the proper side of the analemma. The purpose of the analemmas is to provide a time measurement that takes into account the motions of the sun. Normally, without the analemma, the EOT correction is required to get the mean sun time.
Dan Wenger >However.... >If there is a analemmatic sundial with EOT correction build in. >The location is: Logwood gardens, Kennett Square, Pennsylvania and has the >dimensions of 11.35m x 7.28m and is designed by P.Kenneth Seidelmann. >He made actually two halve dials, one for AM and one for PM. He used the >idea not to have an exact dial, but allowed a little error. In practice >this error is less than 1 minute, so quite acceptable I think. >There has been some publications about this type, but the dial mentioned is >the only one constructed according this idea as far as I know. > >Thibaud Chabot > > >At 23:29 30-11-99 -0500, you wrote: >-----Original Message/Oorspronkelijk bericht-------------- >>Analemmatic dials do not correct for the equation of time, despite their >>name. Those which carry an image of the analemma along their center >>footprint might correct for the EOT at noon, but for the rest of the day. >> >>Good question about the shepards dial. It would be very easy to design a >>shepards dial that is already corrected for the equation of time, but to my >>knowledge, none are. >> >>The EOT does change each year, including leap years, and if you look at the >>dialist's companion program, you will note that there is a "mean" EOT for >>each 4 year cycle. I don't understand all of the factors which slowly >>change the EOT over time, but it may have something to do with the change >>of eccentricity of the earth's orbit. I have no idea whether precession of >>the equinoxes plays a role. >> >>Bill Gottesman >>Burlington, VT >> >>Message text written by "peter ransom" >>>Dear Reader, >> >>I would like to know whether the equation of time is used when an >>analemmatic dial is read. I have pictures of human analemmatic dials where >>the position of the gnomon is indicated by an analemma, and some where the >>position of the gnomon is indicated by dates on a central straight line. >>Both cannot be correct! My gut reaction is that the analemma takes care of >>the equation of time automatically, but would like confirmation of that, >>and >>whether the analemmatic dial with dates on the straight line need equation >>of time correction. >> >>Does one use the equation of time on a shepherd's dial? >> >>What happens to the e. of t. in a leap year? >>Should we have a new e. of t. each year? >> >>Thanks for your help. >> >>Carpe horam >> >>Peter Ransom< >> >> >----------------------------------------------------------------- >T. & M. Taudin-Chabot, home email: [EMAIL PROTECTED] >(attachments max 500kB, in case of larger attachments contact me) Daniel Lee Wenger Santa Cruz, CA [EMAIL PROTECTED] http://wengersundial.com http://wengersundial.com/wengerfamily
