Good for you Bob. I'm glad you joined the List because I'm getting tired of forwarding you all those e-mails! You wrote a very nice letter and I'm sure you will be warmly recieved by the group. By the way, mixed in with all those emails was one that said that I have your measuring tape! Don't worry I'll get it back to you.
John John L. Carmichael Jr. Sundial Sculptures 925 E. Foothills Dr. Tucson Arizona 85718 USA Tel: 520-696-1709 Email: [EMAIL PROTECTED] Website: <http://www.sundialsculptures.com> ----- Original Message ----- From: "Bob Hough" <[EMAIL PROTECTED]> To: "sundial_list" <[email protected]> Sent: Monday, April 15, 2002 7:04 PM Subject: Analemmatic Sundial Error > 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 > > > > > > - > -
