Hi Gianni, Thank you for posting the azimuthal dial with "double dates". It is very helpful to see possible lines.
There is an excellent article in the June 1996 issue of the BSS on "Azimuth Sundials Horizontal and Vertical" by G. Fantoni. The vertical dials would be very visible for time during the day, which was the original problem posed by John C. The style for such dials is a vertical "wire" that is parallel to the plane of the dial and vertical. The dates are horizontal regions on the dial - pick the date and read the shadow among the hour lines. I have a south vertical wall that declines 26 degrees to the west. I know that surface is equal to a horizontal plane at 18 South latitude with a few hours different in longitude. Does anyone know if I could design an azimuth dial for 18 deg S and shift the hours for difference of longitude and use it on that wall - with a style that is perpendicular to the surface - pointing to 26 deg west of south? Just a thought -- Warren Thom (42N 88W) Gianni Ferrari wrote: > Hi John , > if in an azimuthal sundial we take the circles as you propose we get for > every month a point. > If we connect these points we get some hour lines (Standard or Mean Time ) > that have the shape that you can see in the two figures attached. > In the pictures the lines are made by segments and are not smoothed but a > better result is gotten taking a point (a circle) every 15 days. > > In the pictures the radii are 20 cm for June, 30 for July, 40 for May, 50 > for August, 60 for April, 70 for Sept, 80 for March, 90 for Oct, 100 for > Feb, 110 for Nov, 120 for Jan and 130 for December. The pole is high 150 > cm > In the second image I have tilted the pole toward North to form an angle of > 60 degrees with the horizontal plane. > The figures have been gotten with my program SUND98P distributed with the > issue of September 1998 of The Compendium. > > The curves are very condensed in summer : I would have to make some other > test to get good results aesthetically > > Best > > Gianni Ferrari > > --------------------------------------------------------------------------- > Ing.Gianni Ferrari > Via Valdrighi, 135 > 41100 - MODENA (ITALY) > EMail : [EMAIL PROTECTED] > http://members.tripod.com/meridiane/index.htm > ---------------------------------------------------------------------------
