Sundial calculation

Wall sundial at Royal Square in St Helier, Jersey

Wall sundial at St Helier, Jersey

Wall sundial in Royal Square at St Helier, Jersey, Latitude 49.1839° N, Longitude 2.1057° W. The inscription reads: REGULATE YOUR CLOCKS BY THE SUN DIAL. CORRECTION MUST BE MADE FOR THE EQUATION OF TIME WHICH IS GIVEN IN ALL THE ALMANACKS.

This beautiful sundial is set into the wall of the old Picket House in Royal Square, St Helier, Jersey. Historical records show it was made by a talented Jerseyman called Elias Le Gros in the 1820s. In spite of being plastered over at one time by the military authorities and then restored again in 1875 after a public outcry over the dial’s obliteration, it is now in excellent condition, as our photo shows. Our host for lunch that day told us: “The dial is much admired but of course it isn’t accurate.” Poor old Elias Le Gros, now was the time to rescue his reputation! Continue reading

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Restoration of a small brass garden sundial from the 1930s

Brass sundial from the 1930s restored with a new gnomonThis small brass garden sundial had lost its gnomon. It is dearly loved by its owner who has known it since childhood, and she wanted to have it restored. As often happens at different times the family moved home and the sundial moved too. Continue reading

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Rustic stone sundial in an Edinburgh garden

A stone sundial carved in rustic style for an Edinburgh garden

This sundial is delightful. It is the first piece of work by someone in Edinburgh who is learning to do stone carving. It is a very good sundial and they should be proud.

A sundial carved in stone is always special. This sundial is the first piece of work by a stone carver who has begun learning the craft of carving for their own pleasure. The result is very good. The rustic design suits the sunny spot on their slightly overgrown wall in the garden in Edinburgh so well.

Even a rustic design has to follow the sundial rules for the angles of lines on the dial and the angle of slope of the gnomon. Continue reading

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What is the declination of the wall for a sundial

The diagram illustrates a method for calculating wall declination.

Knowing the declination of the wall (WD) is important for designing a sundial. The basic calculation is azimuth angle (AA) minus protractor angle (PA) plus 90°. You can repeat your measurements for accuracy. Do ask for help if you are unsure.

“What is the declination of the wall for a sundial?” A stone sculptor asked us just this question recently . It is a good question because you must know the declination if you are making a sundial that is accurate for the wall. The sculptor was not confident about their own measurements and calculations so they asked us for help. Continue reading

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