Article of the month February

New Dialling Scales

Dialling scales were developed centuries ago. They enable one to draw a sundial in moments.
See Article of the Month for November 2004 on this site.

Since then, various models were invented. Recently, Fred Sawyer of the USA added a new development, which is shown here.
Note: This is just one example out of many possibilities.
The advantage of this model is that it may be used in the higher latitudes.

The latitude scale is split in two parts: the right for the range from 0 to 45 degrees, the left for the range from 45 to 90 degrees.

The time scale now has a different symmetry point; in this example at an hour angle of 50.768480 degrees.
Note that in use, the 12-hour mark is still on the noon line of the sundial.

Store and then open in your own application for a larger image.

The use of these scales in latitudes from 0 to 45 degrees is the same as that of the classic dialling scales.
The zero point is the 0-degrees mark on the scale from 0 to 45 degrees.

The use in latitudes of 45 to 90 degrees is shown in the example below, using a latitude of 60 degrees.

The latitude is plotted on the horizontal line from the 60-degrees mark to the mark for 60-45 = 15 degrees.
The hour scale is placed with its 12-hour mark on the noon line of the sundial.
All hour lines may now be drawn directly.