How to Make a Sundial

Sundials have been used for thousands of years to tell time. You can make this simple horizontal sundial in just an hour or two.

Difficulty:

Moderately Easy

Instructions

Things You'll Need

• Protractor And Drafting Compasses
• Maps
• Laser Printers
• Local Newspapers
• Internet Access
• Pencils
• Felt-tip Pens
• Pens
• Common Nails
• Disk Of Wood Or Cardboard
• Hammers

1. Use a disk made from wood or heavy cardboard for the base of your sundial. Mark its center with a pen or pencil.

2. Choose an item for the gnomon, or hand, of your sundial. This is the part of the sundial that casts a shadow onto the dial. A pencil, pen or nail (for a wood disk) can each work well.

3. Determine your latitude. This number can be found on either a map or on one of many Internet sites that will calculate your latitude for you.

4. Insert the end of the gnomon into the disk at its center. The angle of the gnomon relative to the face of the disk should equal your latitude angle. Use a protractor to verify that the gnomon is at the correct angle to the disk.

5. Find an Internet site that will allow you to input your latitude information and will then produce a horizontal sundial face diagram that is specific to your latitude (try physics.uwyo.edu/~rberring/sundial.html)

6. Print out the dial face diagram. The diagram will consist of a horizontal line with lines radiating upward from its center.

7. Place your disk onto the diagram so that the gnomon lines up with the radiating vertical line. The center point of the disk should rest where the horizontal and vertical lines meet.

8. Use a felt-tip pen to transfer the lines from the diagram onto the disk. The lines should radiate from the center of the disk outward. Label the lines on your disk to indicate the hour that each represents. Use the diagram as a guide.

9. Take your sundial outside and point the gnomon of your dial due north. The resulting shadow should fall along the appropriate hour line.

Tips & Warnings

• Use a gnomon whose length is approximately ½ to ¾ the diameter of the disk.

• Use these instructions for any location in the Northern Hemisphere.

• Find true north (which differs from magnetic north) by placing a long stick straight into the ground at true midday. The shadow cast at exactly this time will point in the direction of true north. Determine true midday by first converting the sunrise and sunset times into military time (i.e., 6 PM = 1800). Add these two times together and divide by 2 to get the true midday time.

• Find the sunrise and sunset times in your local newspaper.