RE: date scale

[John Carmichael]

Hi Tracy & Others:   While researching mosaic dials I recently came across this beautiful but severely flawed analemmatic sundial in Sabadell Spain.  Notice that it incorrectly has an analemma instead of a date line.  Also, it is enormous measuring 12 x 8 meters.  The user’s shadow is way too short to reach the hour markers.  This otherwise beautiful mosaic dial must have cost a lot of money to build so it really is unfortunate that these common design errors continue to be made in new analemmatic sundials.  Even more surprising and disturbing is that it was designed by the Vice President of the Catalonia Sundial Society.  See this website: members.aon.at/sundials/bild36e.htm   John Carmichael       Hello Tracy,   Chris provides some good advice. The center line on the N/S axis is correct. The noon hour point offset we assume is the longitude correction. This shifts all the hour points accordingly. Your size, 33 ft major axis is fairly large. Appropriate for your design perhaps but be aware of the short shadow lengths in the summer for a person as the gnomon. Also be aware that the normal analemma shape provides a time correction E/W only. This works for noon but for the corrections in the N/S direction for other hours, AM and PM go in opposite directions. Two analemmas and a split dial can provide better correction but generally this is not worth the effort.   From your relatively local "palouse.net" email address I wonder if you may have seen the Skaha Lake analemmatic sundial near Penticton BC. It is billed as the "Worlds Largest Analemmatic Sundial". In my opinion it is too large and falls into the "analemma correction for an analemmatic sundial" trap. But it is a great point of local interest on the beach.   Have you considered seasonal markers that use the dial to tell when and where the sun rises and sets throughout the year. I consider these to be a simple and useful additional feature for analemmatic sundials . Ok, I am biased but...   There is some useful information on such things as shadow lengths and seasonal markers on my fairly primitive personal website http://www3.telus.net/public/rtbailey/    Regards, Roger Bailey Walking Shadow Designs N 48.6  W 123.4 Sidney by the Sea, BC    -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]On Behalf Of Tracy Paine Sent: October 26, 2006 5:55 PM To: sundial@uni-koeln.de Subject: date scale Hello Thank you Chris. In regards to your question, the major axis of my sundial is 33 feet. I used large basalt rocks for the hour marks. I tried to send a picture of it here, but the file was too big I guess. I plan to mosaic the top of the concrete date scale after it is cured. I would like to depict the analemma itself, colored according to the seasons with the months marked around it. Tracy

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