I am joining the sundial mailing list a little late in the discussion, but here is the situation.
Last week my wife and I visited the Flandrau Planetarium to see the very nice dial that John Carmicheal did and also to check out the analemmatic dial on the sidewalk in front of the building. The Flandrau analemmatic dial features an analemma for the dateline, instead of a straight line. We know that may compensate for the EOT at noon but not during the rest of the day. But also, I felt that it was out of proportion. That is to say, the summer solstice seemed too close to the ellipse. I e-mailed John and mentioned that I was going to go back and measure it. John told me about the current discussion and that he intended to measure it himself, so we met there today and made the basic measurements together. We met with Neil McSweeney and Rob Vugteveen of the planetarium and David Harvey, the original designer. They were all very congenial and now understand the problems and are looking forward to a recommendation for correcting the situation. John and I are both running our measurements through our design tools. John uses DeltaCad and I use PostScript (although John has convinced me to try DeltaCad). We will post our findings and make recommendations to the Flandrau management for correcting the situation. Several years ago I was analyzing the analemmetic dial at the US Air Force Academy planetarium. It also has an analemma for a dateline and also has the solstices out of proportion. I discussed the subject with Mickey Schmidt, the director of the planetarium, and he said he had contracted an architect from Denver to design the dial and assumed it would be correct, but found out later on that it had problems. However, it is brass imbedded into granite and will probably stay that way. At that time, to prove to myself that an analemma for a dateline will compensate for EOT at noon but not the rest of the day, I wrote a PostScript file that depicts both types of date lines, with shadow lines for two different dates, Nov 4 and Jul 26, which are on opposite sides of, and ends of, the analemma. So, I found my old file and updated it for the longitude/latitude of the Flandrau dial. If you would like to view the results, I transferred a PDF file to a special folder on my web site. It can be seen at: http://mywebpages.comcast.net/houghbob/sundials Robert Hough ShadowMaster Tucson Arizona 111W 32N -
