PBS
Pbs Teachers: Galileo's Battle for the Heavens Plotting Sun Spots
For this activity, students follow in Galileo's footsteps as they examine the nature of sunspot cycles, define solar minimum and solar maximum, and graph data for a solar cycle. Then they will predict the next solar maximum and when the...
NOAA
Noaa: Ngdc: Sunspot Numbers
This brief article examines the historical work on sunspot recording by Rudolph Wolf. Also discusses how sunspot numbers are calculated today and provide graphs of sunspots numbers from past years.