Article of the month November

Dialling scales

Draw a sundial in a moment - use dialling scales!
Their use dates back to the 17th century.

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Draw a XII-hour line and the two VI-hour lines perpendicular to it.
Using the latitude scale, mark off the desired latitude on both sides on the VI-VI line.
Place the hour scale over the marks in turn, while keeping its XII-hour point on the noon line.
Draw the points for the wanted hour lines.

The figure below shows the construction for a horizontal sundial for 40 degrees north latitude.
For the same sundial in the southern hemisphere we just interchange the rulers.