Take a circular strip out of which hour numerals have been cut, place this hoop in the equatorial plane on a sundial face, and we have a sundial that reads time by lighted numbers on the meridian line.
The principle was long known, but nowadays more and more sundials like this emerge.
Below you see a photograph of such a sundial in Australia. The sundial face is the polar plane directed north.
Observe how the hour figures run the other way ‘round, compared with the situation in the northern hemisphere.
The same designer made the sundial that we will describe next. The principle is the same.
The sundial consists of two apparently detached elements:
- the equatorial band with the cut-out hour numerals
- a central sundial face, supported by two children’s figures who represent the grandson- and daughter of the designer.
Together, they form a very attractive sundial.
The curved sundial face also shows an equation-of-time loop around the meridian line, enabling conversion to clock time.
But now to the title of this page: A clock for an indicator.
The hour designators in the equatorial band are cutouts in the shape of a clock dial:
- a complete clock with 12 hours for each whole hour
- half a clock, with 6 hours, for each half hour in between
and each clock complete with an hour hand.
And as if that is not enough, between all these clocks, small triangles mark the quarters.
The figure below shows the figures projected onto the sundial face.
To the left is the twelve-o-clock dial with the hour hand straight up; to the right is the image of the twelve-thirty dial with the hour hand shifted half an hour ahead.
In between, the quarter-hour triangles are visible.
It is slightly over quarter past twelve.
Notice how the light-image moves to the left. In our country, it would move to the right.
The different clocks, each with its hour hand half an hour further on, are easily recognized in the last photograph.
Overall, this is a splendid idea for the realization of a sundial indicator.
Our member Folkert Visser of Spain made and sent the four photographs.
Bill Newman of Australia is the designer of these sundials.
Fer de Vries
English translation: RH