Spot-on Sundials in Brass

Setting up your Spot-On Sundial

Before setting up your Spot-On Sundial, please read the pages on "Finding the time of local noon" and "Finding your latitude and longitude"which you will need to set up your sundial accurately.

Unpack the box carefully and check the items listed are all present

  • A, C and F - the circular dialplate (A) attached to the square baseplate (C) with the centre screw (F)
  • B - these instructions (not shown in picture)
  • D - the gnomon made of two plates with a narrow air gap
  • E - the gnomon retaining clip,
  • G - the tightening tool
  • H - 4 brass screws for attaching the square baseplate to a plinth or stand.

Place the two lugs on the tightening tool into the holes on the centre screw, and rotate it anti-clockwise. (It helps to put your other hand on the tightening tool above the centre screw to prevent the lugs from disengaging). After a few turns, you will be able to turn the centre screw by hand, remove it completely, and separate the circular dialplate (B) from the square baseplate (A).

You now have the 6 components of the sundial and the 4 tightening screws as shown in the illustration and identified by the letters in panel 1c above.

If you have model E (San Francisco) , F (Los Angeles), or G (New Orleans you should place the centre screw back in the hole in the centre of the dialplate, and secure it with a piece of tape before proceeding to step 2. You need to do this because the low angle of the gnomon on these models will not permit you to insert the centre screw with the gnomon in place as described in step 6

Hold the gnomon as shown and slide the thin end with the two holes into the dialplate, so that it is slanting towards the centre as shown. The gnomon is a tight fit in the dialplate, in order to ensure it is at the correct angle. It is best to start with the acute angle, and then "rock" the inner angle into position.

Turn the sundial over. The two holes in the gnomon should both be clear of the baseplate. Position the gnomon retaining clip so that the "arms" are flat on the baseplate, and the "hoop" is raised off the baseplate as shown in panel 3a. Then slide the clip through the two holes in the base of the gnomon.

Push the gnomon retaining clip into the holes as far as is possible by hand. (The arms are very slightly tapered to ensure a tight fit.)

Set up the plinth on which the sundial will rest. Ensure that it is completely level in 2 directions at right angles to each other. It is worth taking trouble with this since the accuracy of your sundial depends on it. (it is particularly important to get it level in the east-west plane, since an error of 1 degree in the level will lead to an error of 5 minutes or more in the reading; an error of 1° in the north-south plane will only result in an error of 2 minutes or so)

Place the baseplate in the desired position on the plinth, and mark the position of the screws on the plinth using a pencil through the screw holes on the baseplate.

If you are certain that your plinth is level to within ½°and you want to compensate for the small difference between the latitude stamped on the dial and your actual latitude, so that you get the maxim mum possible accuracy from your Spot-On Sundial, you should read now our advanced setup page.

Drill out the screw holes in the plinth.

Screw the baseplate down onto the plinth with the 4 screws. Place the dialplate on top of the baseplate, and line it up so that the centre screw will pass through the dialplate and locate in its correct position in the baseplate. Insert the centre screw and tighten it by hand, leaving the dialplate free to rotate.

For the final stage of the setup

1. Set your watch accurately by a radio time signal.

2. Find out the time of solar noon at your location using our unique Solar Noon Calculator.

3. When your watch reaches the exact time of Solar Noon, rotate the dialplate until the shaft of sunlight shining through the slit in the gnomon lies exactly along the dotted noon line. Then tighten up the centre screw further with the aid of the tightening tool. Your sundial is now set.
4. Please look at the pages on Reading the Spot-On Sundial and on Looking after your Spot-On Sundial if you have not already done so.

Spot-On Sundials is the trade mark for sundials designed by Piers Nicholson andincorporating the unique "line of light" which enables them to be set up (and therefore read) to great accuracy. Spot-On Sundials are also available in stainless steel.