"SNOURTH-ometer"

In order to correctly position your sundial for use, in many cases you will need to determine true north or south...or true "SNOURTH". This is not the same as magnetic north or south. This is the direction of the celestial pole. There are a number of ways to do this but the device provided for you here will allow you to use one of two methods or both. These are:

• The equal altitudes method.

• The local apparent or solar noon method.

Figure 1 illustrates the template for the "SNOURTH-ometer". This device will work in both the Northern and Southern Hemispheres. There are two sizes available. The circular "SNOURTH-ometer" is the smaller of the two and can be positioned arbitrarily but will require a shorter shadow caster or "SNOURTH-iscope". The semi-circular "MEGA SNOURTH-ometer" should initially be positioned  using a magnetic compass to ensure the shadow will always fall on its surface. A taller "SNOURTH-iscope" can be used and a longer shadow will result. Try to obtain as long a shadow as possible no matter which device you use.

Figure 1: "SNOURTH-ometer" (CAD)

A number of "SNOURTH-iscopes" are provided. Depending upon your location and the time of year you will require "SNOURTH-iscopes" of different lengths to get a good shadow. Make these carefully as the straight edge must be as vertical as you can make it.

EQUAL ALTITUDES METHOD

At equal intervals of time before and after noon the sun will be at the same altitude. The exact times do not matter. The circles on the "SNOURTH-ometer" will help you determine this.

Position the "SNOURTH-ometer" you will be using at the location where your sundial will be installed. Make sure that it is perfectly level and secured so that it will not move. Select a "SNOURTH-iscope" and place its straight edge at the centre of the cross located in the small circle making sure that it is vertical. Secure it in position. In the morning, observe the shadow of the tip of the "SNOURTH-iscope" and mark a point when it is on any circle. You can mark points on any number of circles. In the afternoon, again observe the shadow of the tip of the "SNOURTH-iscope" and mark the points when it is on the same circles that were marked in the morning. Draw a line between the two points marked on a given circle. Find the centre point of this line. Draw a line through this point and the centre of the cross located in the small circle. You have now determined the true north or south line at your location. This can be repeated with any of the other marked circles and you should obtain the same line.

LOCAL APPARENT OR SOLAR NOON METHOD

Position the "SNOURTH-ometer" you will be using at the location where your sundial will be installed. Make sure that it is perfectly level and secured so that it will not move. Select a "SNOURTH-iscope" and place its straight edge at the centre of the cross located in the small circle making sure that it is vertical. Secure it in position. You will need to determine the time local apparent or solar noon occurs at your location. You also need an accurate watch. At precisely solar noon mark a point on the "SNOURTH-ometer" anywhere along the straight edge shadow line of the "SNOURTH-iscope". Draw a line through this point and the centre of the cross located in the small circle. You have now determined the true north or south line at your location.

It is good practice to repeat the method you are using on another day to confirm the first line you established. You can also use both methods on the same day as confirmation. If there is a large difference repeat the process. If the difference is small you can use and average position between the established north-south lines to determine the position of the final line.

If you would like to have the "SNOURTH-ometer"  you can download a pdf file of a kit that you can put together. It is very easy to do.

"SNOURTH-ometer"

Happy Dialling!