EQUATION OF TIME ENGRAVINGS

Equation of time graphs can be incorporated into the sundial design for a small additional charge, or engraved on a separate brass or slate plate

The standard brass Equation of Time graph is shown on the left is available from stock. The 3mm thick plate is 125mm x 75mm (approx 5" x 3"), and has a matt finish. The easiest way to fix is with an epoxy resin. Also available with four screw holes.

The slate Equation of time plaque on the right was specially made to fix at eye level below a large slate wall sundial commission. Sundialman can custom make an equation of time a plate in brass or slate to your requirements.

It is possible to engrave an EOT plate that will compensate for the longitude difference. Hence watch time can be determined directly from the chart.

SUNDIAL TIME

TIME (MEAN & TRUE)

The sundial shows true time. A clock or watch can only show mean time. The difference between the two is shown by the equation of time.

To enable a watch to show the correct time it is necessary to make 2 adjustments to get GMT. Three adjustments are required during the summer when the UK has BST.

1. Add or subtract the Equation of Time value (EOT), as shown on the EOT graph for the current date. When graph shows SLOW, ADD minutes to watch to get true time.

2. Adjust for longitude.

For each degree of Longitude EAST of the Greenwich Meridian ADD 4 minutes.

For each degree of Longitude WEST of the Greenwich Meridian SUBTRACT 4 minutes.

3. During British Summer Time SUBTRACT 1 hour.

You now have true time as shown on the sundial

THE SUNDIAL MAKING PROCESS

Using solid brass and local slate Nick produces a unique range of sundials. Each sundial is individually designed and calibrated prior to manufacture. The exact position of each time line has to be individually calculated. Brass sundials usually show quarter hours, slate sundial the hours only. Alternative increments can be provided on request. The correct hours will be engraved for your location, dials made for further north will have more hours because of the longer summer days at these latitudes than in the south. This is the way traditional sundial makers of past centuries would calibrate the state of the art time piece of its day. Your sundial will be made for your location, using the postcode or town given when ordering.

The dials are made to show true time (local apparent time). If you wish to specify an alternative, Nick will be happy to discuss your requirements.

A. On receipt of your order Sundialman finds the Latitude from Bing or Google Maps.

B. Using this Latitude the angles of the hour lines are calculated.

C. The Gnomon is made from best quality brass. The gnomon angle is crucial to telling the correct time. This has to be the same as the Latitude at the sundial location. For example, on a 29cm dial made for London (Latitude 51deegrees 30 minutes North) the tip of the gnomon will be 4 mm higher than one made for Brighton (Latitude 50 degrees 50 minutes North) just 50 miles further south.

D. The best Welsh slate or 3mm thick brass are selected for the plate of the dial. It is cut to the exact size and shape you require before being engraved or carved. Any wording or design can be included on the dial. You will be sent a copy of the design before work starts.

Nick Canfield, Sundialman, The Smithy, Pentrefoelas, Betws-y-Coed, LL24 0HY. Tel.(01690) 720288 Mob. 07788 543 550

E mail:- nick@sundialman.co.uk