Provisional Sunspot Relative Numbers
The provisional sunspot relative numbers are derived from the daily sunspot drawings.
For this purpose the solar disk is projected with a diameter of 25 cm onto a drawing desk. The also called Zürich Number or Wolf Number R is calculated
R = k(10g+f)
k...Correction factor (which depends on the actual seeing conditions and the used instrument) to make observations from different places comparable
g...Number of sunspot groups
f...Number of spots (umbrae) observed
The Kanzelhöhe Provisional Sunspot Numbers Reports are available as ASCII Files.
Definitive Sunspot Relative Numbers
The provisional numbers are compiled and reported monthly to the Solar Influences Data analysis Center (SIDC) at Brussels.
Contributions of several observing stations are averaged in an advanced form and published as definitive sunspot numbers.