Expecting the worse, I ordered a calibrated photo cell from the Edmund Scientific Company. The photocell has a linear output and the intensity of the light is directly related to the current on a digital meter. I placed the photocell in a glass jar and placed it on the roof of my classroom. While the moon was coming in front of the sun, the current on the meter began to go down. I had 2 students take turns writing down the current every few minutes. The change in the amount of light level caused by the changing of the cloud thickness did not seem to have caused any great variations in the results which clearly showed the time of the maximum eclipse of over 90%.
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© 1998, James A. Petrait,