sundial mathematics

A modern altitude sundial after Erasmus Habermel

A modern circular altitude sundial after Erasmus Habermel of Prague

Modern reconstruction of a 16th century altitude sundial for studying its mathematics and accuracy. An altitude dial uses the height of the sun to find the time. The dial is double-sided with the two half-years back-to-back.

Erasmus Habermel was a renowned scientific instrument maker working in the court of Emperor Rudolf II in Prague in the 16th century. He made instruments for all disciplines including astronomy and navigation. One of his sundials is an altitude dial in the clocks collection of the Augustine Museum in Freiburg im Bresgau*. It is an elegant circular dial and the mathematical construction is intriguing. Continue reading

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Calibrating a new obelisk sundial in stone

Inclined test dial facing east

This dial stone is a test piece for the new obelisk sundial, and is on a board at the correct angle for one of the faces of the obelisk. It faces East and inclines 61° to horizontal so the shadow of the temporary plastic gnomon will show the time.

Obelisk sundials carved in stone were popular in Scotland in the 17th and 18th centuries. Quite recently stonemasons in Fife have done the work to carve a new obelisk sundial for one of their clients. Its dials have remained blank for mathematical calibration. Macmillan Hunter are responsible for the calibration and have supplied detailed dial instructions and drawings for the mason to use together with the required set of geometric bronze gnomons. Continue reading

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Historic Scottish Stone Sundial Restored

Scottish stone sundial restored

The octagonal base and baluster shaft support a carved cube stone. Before restoration the stones were covered in moss lying on the ground in the owner’s garden. The bronze horizontal dial is new.

Stone sundials were common in Scotland in the 17th and 18th centuries. They stood in the gardens of great houses, and in public places. The geometric form of the sundial would reflect the popular interests of the day in science and mathematics, and many displayed complex multiple dials. Originally this particular sundial may have belonged to a country estate near Falkirk. The present owner has had it for many years and in 2023 decided to restore it. Continue reading

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An armillary sundial in early morning

An armillary sundial in early morning

This is our new sundial design. It stands in our garden among the plants. It is early morning and the sun has just reached the centre band where you read the time.

An armillary sundial has a wonderful form. It has mathematical rings creating beautiful shapes with circles and lines. The sundial in the photo has just begun to catch the early morning sun in the garden.

The sundial gnomon is the slanting rod in the centre of the rings, and the wide sweeping band is where you can read the time. These features are the same as other armillaries, but our design has special secrets. Continue reading

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Modern techniques for a replica sundial exhibit

A first trial assembly of the gnomon and base plate in position on the dial

Details for making the sundial came from archive records and photos. This image shows the design and successful first assembly of the new parts.

The replica of a 19th century lighthouse sundial we are making will be part of a mobile exhibition. It is progressing well. Lighthouse sundials were made by skilled instrument makers, who worked mainly with hand tools. We are using modern techniques for cutting out the metal and etching the intricate design on the dial plate. The picture shows our first trial to assemble the dial and gnomon parts. 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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Supreme Scottish Sundial at Glamis Castle

Sundial at Glamis Castle with 80 dials on the polyhedron

The polyhedron is an upper part of the sundial with 80 dials, and an earl’s coronet on top. Four lion sculptures at a lower level carry dials in their claws.

In the extraordinary world of Scottish historic sundials, the supreme sundial monument stands at Glamis Castle. It is the tallest and grandest sundial and is in the grounds of one of the most beautiful castles in Scotland. In August 2020 a TV crew were filming there for a future series. They asked Alastair Hunter to Continue reading

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Restoration of the obelisk sundial at Drummond Castle gardens

THE DRUMMOND CASTLE OBELISK SUNDIAL

The sundial consists of 61 multiple dials on raised panels and in sunken hollows. The date of the sundial is 1630. It has been made as an exhibition piece to show all of the sundial mathematics of its era.

The sundial obelisk at Drummond Castle in Perthshire has a long and distinguished history. It has its place in the architecture of the ancient castles and houses in Scotland. It is connected with the very earliest days of the British Sundial Society (BSS). And it is one of the most important free-standing sundials in the British Isles from the early 1600s still surviving.

In 2017 after almost four hundred years outdoors the sundial was showing serious signs of the stone deteriorating. The whole structure was feared to be unsound. Making it safe had become urgent. Continue reading

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