Labs from YSI 94 :
Individual Horizontal Sundial 2 (Cloud/Rain Activity).

April Whitt
CARA Yerkes Summer Institute, August 1994

This is a lab and a Teacher's Guide that's missing a graphic.

This sundial will work best at 42 1/2° latitude, the latitude of Yerkes Observatory.


This page, thin cardboard, scissors, glue


  1. Glue the sundial and gnomon pieces to a sheet of thin cardboard. Let dry.
  2. Cut out the sundial and the gnomon carefully.
  3. Glue the gnomon to the sundial on the 12:00 Noon line, matching points (a) and (b).
  4. Set the sundial up outside or in a sunny window level to the ground. Point the Noon line and the gnomon directly North. Adjust the sundial by comparing the time you see on the dial with the time on a clock and turning the sundial until the times most nearly match.
  5. If you measure the time at different times of the year, how accurate will your sundial be?


Sundials measure Local Apparent Time, which depends on the position of the sun in the sky overhead. You will need to make an adjustment to the time you read on the sundial to get Standard Time. Many astronomy books and the books listed below give the corrections factors required to make this adjustment.

For more information about sundials, try these titles:
Sundials, Their Theory and Construction by Albert E. Waugh
Sundials by Roy K. Marshall

Important Disclaimers and Caveats: