Directions for Making a Sundial

Sundials are a feature in many gardens.

Sundials are an ancient and immediately recognizable means of telling time. There are many forms of sundials, the garden or horizontal sundial being the most common, all of which can be constructed from very basic materials. A homemade sundial may not be as versatile as a watch, but it never needs new batteries and will tell relatively accurate time as long as it's sunny.

Things You'll Need

• Cardboard
• Craft knife
• Country map
• Protractor
• Ruler
• Glue
• Pen
• Flat outdoor surface
• Magnetic compass

Instructions

1. Cut out an 8-inch square of cardboard. This will form the base of the sundial.

2. Locate your latitude on a map of your country.

3. Cut out a triangle from one corner of a piece of cardboard to form the gnomon, or vertical piece of the sundial. To do this, measure 6 inches across the cardboard's bottom edge from the bottom-left corner, then place your protractor at that point and measure an angle equal to your latitude from the bottom edge. Draw a line at this angle from the 6-inch marking to the left side of the cardboard, then cut along this line.

4. Draw a line on the base of your sundial parallel to, but 1 inch away from, one of its sides. Measure and mark the center point of this line. This line will be the sundial's 6:00 a.m. and 6:00 p.m. line.

5. Draw a line perpendicular to the first line, starting at the center point marking and continuing to the opposite edge, forming a large "T." This will be the sundial's noon line.

6. Turn the base so that the noon line is horizontal, then use your protractor to draw five lines, all emanating from the point at which it connects with the original line, to the edges of the base between the noon and original lines. The lines, measured from the noon line, should be at a 9.4-degree, 19.6-degree, 31.6-degree, 46.8-degree and 66.5-degree angle (for the 11:00, 10:00, 9:00, 8:00 and 7:00 lines respectively). Rotate the base 180 degrees and repeat the process with the same angles for the 1:00, 2:00, 3:00, 4:00 and 5:00 lines, making them symmetrical with the first five.

7. Label the lines along the edges of the sundial, starting at 6:00 a.m. and proceeding clockwise.

8. Apply glue to the 6-inch long side of the gnomon, line it up with the noon line so that the shorter end terminates at the center point of the original line. Press it into place, and allow the glue to dry.

9. Place the sundial on a flat, outdoor surface that is as level as possible.

10. Use a compass to point the noon line of the compass directly north.

Tips & Warnings

• Due to irregularities in the Earth's orbit and how time zones are configured, sundial time will sometimes be slightly different from clock time even with a properly made and adjusted sundial. NASA says to keep in mind that sundials will differ from clock time during daylight saving time.

• The angles given for the 7:00-11:00 and 1:00-5:00 lines are calculated for latitude 38, and are usable for much of the continental United States. If your latitude is significantly different from that or you want more specific angles for your location, there are websites that can calculate the angles for you.

References

• "Sundials: Design, Construction, and Use"; Denis Savoie; 2009
• NASA: The Sundial

Resources

• Montana State University: Enter Your Latitude