created by Carl Sabanski
Make a Vertical Sundial - Graphical Method
Vertical Sundial: any dial in which the dial plate is vertical.
The sundial you will be making is a vertical sundial that faces directly south.
Figure 1 shows the relationship between a vertical sundial and the equatorial sundial that is used to create it. Notice that the two sundials have a common style or shadow casting edge that points to the celestial pole. The style is at an angle equal to the co-latitude, or 90°-latitude, relative to the face of the vertical sundial and it is perpendicular to the face of the equatorial sundial. For this to be, the equatorial sundial is tilted at an angle equal to the latitude relative to the face of the vertical sundial.
This sundial is designed for the Northern Hemisphere and the style must point to the North Celestial Pole (True North) or Polaris. To design a sundial for the Southern Hemisphere you need to reverse the numbering of the hours. Instead of the hour numbers going from 6 a.m. to 6 p.m. in the counterclockwise direction they will go from 6 a.m. to 6 p.m. in the clockwise direction. Also the style must point to the South Celestial Pole (True South).
This sundial will tell solar time but not clock time. You must learn about longitude correction and the Equation of Time to correct your sundial reading so that it will give you clock time.
Figure 1: Vertical Sundial (CAD)
It would be difficult to project the hour lines of the equatorial sundial shown in Figure 1 on to a vertical plane to create the vertical sundial. A graphical method is available to do this on a flat surface, your piece of paper. Follow these instructions and in no time you will have your very own vertical sundial and it will be designed for where you live.
What do you need to know? All you need to know is the latitude of where you live. Now let's make a vertical sundial.
A vertical direct south sundial in the Northern Hemisphere and a vertical direct north sundial in the Southern Hemisphere can tell the time between 6 a.m. and 6 p.m.. Check out The Sundial Primer page "Sun Charts" for some interesting information.
Congratulations! Your sundial is now ready to use. All you need to do is find a sunny spot and find the direction of true north, that is the celestial pole. Make sure that your sundial is vertical and that the gnomon is pointing to the celestial pole. To find true north please go to "Finding True North" at The Sundial Primer.