Article of the month September

Construction of
a combination sundial

In the column “Work of members”, there is a combination horizontal-vertical sundial by Dees Verschuuren.
See: Work of members, 2005 archive, month 09.

Here, we show the construction of just such a sundial, but with an added equatorial dial.

We chose a latitude of 52 degrees North, and the figure below shows a side view of the combination dial.

Take three postcards and tape them together.
In the centre card, draw a horizontal centre line and a circle.
On all three cards, draw the vertical centre line through the circle.
Cut the circle along the dotted line. Later, you will fold the centre card double along the horizontal centre line, but leave the circle part.
In the centre card, draw 24 hour lines, spaced 15 degrees.

To the side of the cards, draw two right-angled triangles with one corner of 52 degrees.
Make sure that side DE equals half the width of a postcard.
Draw the VI-VI lines twice to find the foot of the pole style.
Draw the other hour lines, and fold the cards.

This leaves only a style to be added. The finished three-sundial model shows the relationship between the three planes quite clearly.

Another example of such a combination sundial is shown below.
Here, a polar sundial was added as well.

Model by Tony Moss, UK.