Setting up your sundial

 

Your sundial will read accurately if three conditions are fulfilled:

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1. The sundial is placed on a true horizontal surface.
   You can check this with a spirit level, preferably a long one

2. The gnomon (which casts the shadow) is makes an angle equal to the latitude with the base plate
   Your sundial has been manufactured to this angle, so you do not have to do anything for this.

3. The gnomon is pointing to true North i.e. the North Celestial Pole in the Northern hemisphere)
   This is the most difficult condition to fulfil – see below

 

Traditional methods for determining true North are discussed in an article “How to set up a horizontal sundial.  Piers Nicholson Sundials have a unique feature which enables them to be set more accurately and quicker than any of these methods.

 

When the sun is highest in the sky, it is due South.  This time is called solar noon.  At solar noon, a line of light will appear, shining through the air-gap in the gnomon of your Piers Nicholson sundial. You can use this to find true North by looking up the exact time of solar noon for your latitude and longitude for every day of the year on our companion website  www.solar-noon.com. Then proceed as follows:

 

1. Lay your sundial on a flat surface, such as a levelled paving stone

2. At the exact time of solar noon, rotate the sundial till you get the line of light.

3. Put a long straight piece of wood along the edge of the sundial (This is your meridian marker, pointing accurately along the North-South line)

4. Hammer in some pegs to ensure that the piece of wood does not move.

5. If you are installing the sundial on a square plinth, lay the base against the piece of wood, so that it is accurately aligned to true North.  (note that plinths placed directly on the ground will not stay horizontal over the years.  It is best to put down a concrete slab to ensure stability)

6. Add on any remaining sections of the plinth.  (The top section will need to have a slot in its surface to accommodate the securing plate and bolts at the base of the gnomon.  If you want a secure fixing, you will need to drill 4 holes to accommodate the M6 threaded bar supplied with the sundial)

7. Place the sundial on top of the plinth, and check visually that it lines up accurately with the meridian marker.  Mark a pencil line along the edge of the sundial.

8. For the easiest fixing, use a modern adhesive spread all over the underside of the sundial, and place the sundial accurately against the pencil line you have just marked.

9. If you need a more permanent fixing, fit the threaded bar into the blind M6 holes on the back of /the sundial, half fill the holes (see section 6 above) with resin, and drop the sundial into place.

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You can see some pictures of this process here