The idea of computing sunspot numbers was originated by Rudolf Wolf in 1848[1] in Zurich, Switzerland and, thus, the procedure he initiated bears his name (or place). The combination of sunspots and their grouping is used because it compensates for variations in observing small sunspots. The relative sunspot number R is computed using the formula (collected as a daily index of sunspot activity):
R=k(10g+s),
where
s is the number of individual spots,
g is the number of sunspot groups, and
k is a factor that varies with location and instrumentation (also known as the observatory factor or the personal reduction coefficient K).