Year 2005

Work of our members

Equatorial sundial

It is well known that the hour lines on an equatorial sundial are distributed quite evenly. The angle between them is always fifteen degrees.
No calculation is involved.
It suffices to know on which latitude the sundial is to serve.

This sundial, however, does not show hour lines, just single points of those lines.
It indicates apparent time, and so the hour points on top and on the bottom of the equatorial disk are directly over each other.
They were therefore replaced by holes in the disk.

The thickness of the style triangle should be taken into account.
The centre for the fifteen-degree angles changes back and forth every six hours.

Because the equatorial dial face is circular, its shadow on the pole style indicates the date.
This way, the sundial is not only a clock, but also a calendar.