SILSO data/image, Royal Observatory of Belgium, Brussels

Yearly mean total sunspot number
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Time range: 1700 - 2014

Data description: 

Yearly mean total sunspot number obtained by taking a simple arithmetic mean of 
the daily total sunspot number over all days of each year. (NB: in early years 
in particular before 1749, the means are computed on only a fraction of the days 
in each year because on many days, no observation is available).  


Filename: yearssn.dat
Format: plain ASCII text

Contents:
Column 1: Gregorian calendar year (mid-year date)
Column 2: Yearly mean total sunspot number.
Column 3: Definitive/provisional marker. A blank indicates that the value is definitive. 
          A '*' symbol indicates that the yearly average still contains provisional 
          daily values and is subject to a possible revision.

Line format [character position]:
 - [1-6]  Year (decimal)
 - [8-12] Yearly mean total sunspot number
 - [14]   Definitive/provisional indicator for monthly numbers