How long are the fluctuations in sunspot numbers ?
The relative sunspot number formula_1 is computed using the formula ( collected as a daily index of sunspot activity ) : formula_2 where formula_3 is the number of individual spots , formula_4 is the number of sunspot groups , and formula_5 is a factor that varies with location and instrumentation ( also known as the " observatory factor " or the " personal reduction coefficient " formula_6 ) .