Hi All, [EMAIL PROTECTED] wrote: > > Clyde, I believe what you are describing is a polar dial. > It is what a horizontal dial would look like if it were made > for the equator. The Lyman Briggs dial at the national bureau > of standards is a polar dial. I think you will have no trouble > finding illustrations of this dial type in any of the > standard dialling texts, and one picture will be worth > a thousand of my words. > > The hour lines do not intersect, and each runs north-south, > all of them parallel to each other. The shadow casting edge > of the gnomon also runs north-south, parallel to the > horizontal surface of the dial below, never intersecting > it (in a non-polar dial the gnomon intersects the dial plane at > 6:00).
The Lyman Briggs dial can be seen at http://www.shadow.net/~bobt/briggs/briggs.htm This is a fascinating polar dial. It includes three faces. The parallel lines for apparent solar time Bill mentions are in the center, and two other faces with half analemmas for standard time are above and below the standard time face. I produced the drawings of the analemmas with the data files I mentioned in the message about .prn files I sent last night. Behind the dial there is another analemma which functions as a noon mark. A spot of sunlight falls on it through an aperture at the top of the dial face. A drawing of this analemma is included on the page. Compare it to the noon mark Ron Anthony recently posted as a DeltaCad Basic file. Best, Bob Terwilliger
