How to Make Sundials

A sundial is a simple and elegant machine used to tell time.

Our timekeeping is based on the apparent motion of the sun across the sky. Even before clocks were invented, humans had ways of keeping accurate track of a day's hours. A sundial is one of the oldest ways of keeping track of time and is relatively easy to construct. While there is no standardized set of materials for making a sundial, some basic design principles must be followed to ensure its efficacy and accuracy.

Print this article

Cardboard (2 pieces)
Scissors
Pen
Protractor
Tape or glue
Computer

Instructions

- 1
  
  Determine your latitude. You may know this already, or you might wish to consult a map.
- 2
  
  Draw an angle on the cardboard equivalent to your latitude. Use your protractor for accuracy.
- 3
  
  Cut out the triangular piece of cardboard that is outlined by your latitude angle. This will be the gnomon, or pointer, of your sundial.
- 4
  
  Draw a line at a 90-degree angle from the base of another piece of cardboard. This is the base of your sundial, and your gnomon will eventually be placed on the 90-degree line. This will also be the line for noon.
- 5
  
  Enter your latitude into an online sundial angle calculator. This will tell you where to draw lines on your base, which will represent the hours of the day.
- 6
  
  Draw the appropriately angled hour lines on the base of your sundial using your protractor.
- 7
  
  Affix the gnomon to the base of your sundial using tape or glue. Make sure it sits exactly on the noon line.
- 8
  
  Place your sundial in an outside area that gets a lot of sunlight, and point it directly at True North. True North is the point on the horizon that the North Star is directly above.

Tips & Warnings

During daylight savings time, add 1 hour to all of your hour readings.
For a sundial with a longer lifespan, use more weather-resistant material, such as plastic.
The time told by a sundial can be slightly different than the time told by a clock. This is due to the way Earth orbits the sun. See the Resources for information about the Equation of Time, which explains this discrepancy.