Build a horizontal Sundial

The hour lines on a horizontal sundial are not evenly spaced, as they are on a polar sundial. Although there are formula available to calculate the angle between the substyle and each hour, here is an easier way for those that are not mathematically inclined.

Instructions to build the model in the photo below:

  • Decide on the approximate size of your dial, lets say 300 x 300 mm.
  • More important, decide on the base length of your style, lets choose 138 mm.
  • Calculate (or measure) the side opposite the angle representing your latitude (for Pretoria that would be 60 mm if the base length is 138 mm).
  • In the middle of a rectangle 60 mm high, draw half a circle with diameter 60 mm.
  • Fill in the hour lines as for a equatorial dial.
  • Place this long strip on one edge of your template and mark the hour lines.
  • On the 12 o'clock line, measure a distance equal to the base of your style (138 mm for this template).
  • From that spot, draw straight lines to the hour markers.
  • Gently score the edge of the style and fold it over.
  • Glue it to the 12 o'clock line.
  • Test your dial in the sun.


Model - Equatorial Dial
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© Helga Nordhoff (2001-2003)