Daily Sun Spot Number

The official SESC sunspot number is computed according to the Wolf Sunspot Number formula R = k(10g + s), where g is the number of sunspot groups (regions), s is the total number of individual spots in all the groups and k is a scaling factor that corrects for seeing conditions.

A sunspot number of zero indicates there were no visible sunspots on that date; a blank indicates that no observations were possible that day.

The sunspot region information used to compute the daily sunspot number incorporates reports from as many as six observatories. These reports are used to form a composite picture of each individual region, taking into account such factors as the time of observation and the quality of seeing.