Hi Helmut & others: I'm sure you probably know this already, but one neat and helpful thing I learned about analemmatic date line construction is this:
All analemmatic dials at every latitude and of every size use the same date line; the only difference is in the length of the line which becomes longer (in relation to the ellipse) at higher latitudes and with bigger dials. But the date line is the same for all. The distance between the date markings is proportionally the same, no matter what length the date line. In other words, you don't have to redraw the date line everytime you design an analemmatic for a different latitude or of a different size. You just need one drawing and you can use it as a template for any analemmaic dial. All you need to do is to change its size. If you use Delta Cad or photocopyers, this is an easy operation. To determine the length of the date line is simple. First, you determine the location of a focus point using traditional methods or Fer's Delta Cad macro. Then draw a horizontal line to the center of the dial (the North/South Meridian). This point is the equinox date on the date line and is at the center of the line. Then draw an angled line from the focus that is 23.44 degrees from horizontal. Where this line crosses the meridian is one end of the date line and marks a solstice date. Measure an equal distance in the other direction an this is the other end of the line and is the other solstice date. The distance between these two points is the length of the line. Then just blow up or shrink the size of your template drawing so that it is the same length. Simple! And this saves a lot of work. Note: Here is a PDF of my Delta Cad Date Line Template. Of course you can change font type and scale if desired. And you can have the option of a clockwise or counterclockwise date notation. Both are shown here. 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: "Helmut Sonderegger" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Monday, June 02, 2003 3:52 AM Subject: your webpage > Fer, > I just had one more look on your webpage with the information on analemmatic > sundials. Therefore my question: Why did you not include the formula for the > date points of the dial? I know, one can see that very easy from the images > there, but perhaps it would be of some help for some visitors of this page. > > sunny greetings > Helmut > > - > Attachment converted: Macintosh HD:ANALEMMATIC DATE SCALE (weeks 1 (PDF /CARO) (00086533)
