A Simple Horizontal Sundial

A two-piece paper sundial for students to print, cut, and assemble.


This paper sundial is intended for all ages, with only two pieces to cut out and fold, and should take less than a class period to construct. It requires scissors, a hobby knife (or a carpenter's utility knife, or a scalpel, if you have dissection supplies), and tape or glue. Many designs of sundial are possible — this one represents the "traditional horizontal" design you might find in garden supply stores.

There are two small steps that need a little bit of care. First, there is a slot to be cut out. Older children who can handle a hobby knife should have no trouble with it, but younger children should probably have help. Also, scoring the fold lines isn't strictly necessary, but it is a great help in making the folds crisp and straight. Again, older children should have no problem with this, but younger children might need some guidance.

Every sundial must be designed for the latitude in which it is to be used, and in the download links you can find several versions that can be adapted to any mid-northern latitude. The "gnomon" or shadow-stick part needs to point at the North Star (or more precisely, the North Celestial Pole), meaning it needs to tilt up at the right angle for your latitude. You handle this by constructing your own pair of fold lines on the gnomon at the appropriate latitude. Also, the hour-line marks will change gradually with latitude, so for the most accuracy, you will want to choose the page representing the latitude closest to you.

To make the dial, choose the page containing the nearest latitude to yours, and print it onto card stock. (If you don't mind a floppy sundial that probably won't last long, you could also just use normal paper.) Mark the fold lines for the gnomon before cutting it out. Draw a line on each side of the gnomon's centerline, starting at the center, and ending at the appropriate latitude mark These become the fold lines along which you will fold the paper to make the flaps that will rest against the bottom of the dial.

Marking the Gnomon for Latitude 35°N

After marking the fold lines for the gnomon, cut out the two pieces of the sundial along the thick black lines, including the incision into the base of the gnomon, and the slot in the dial. If you wish to score the fold lines, place a ruler or other straight edge along the fold line, and run a pin or dull blade (I used the back side of my utility knife blade) gently along the line. Fold the gnomon in half along the centerline, and fold up the two flaps resulting from the construction of the latitude lines. Insert the gnomon through the slot in the dial, and tape or glue it in place. The tip of the gnomon must point north, not south.

Folding the gnomon

Whenever the sundial is in the sunshine, and as long as it is turned the right way, it should give reasonably accurate "solar time". On solar time, "noon" is the exact moment when the sun is due south, at the peak of its arc, exactly halfway between sunrise and sunset. Daylight Savings Time will shift clock time from solar time by an hour, and your longitude within your time zone will also shift your clock time away from solar time. If you live near the center of your time zone, and you are not on Daylight Savings Time, your sundial should be accurate to within 15 minutes or so.

Assembled Dial




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