HRIEUV - High Resolution Imager in the EUV - The squares are examples of little campfires, the circle (left under) denotes the size of the Earth.
Click on the picture to download the movie.
CREDIT: ESA/Solar Orbiter/EUI Team: CSL, IAS, MPS, PMOD/WRC, ROB, UCL/MSSL.
With the introduction of the new series, we stop the extension of the original series as the new series gives a better number, cleaned from past defects. It turns out that the main defect in the series was the use of weighted counts by the main reference station in Zürich and now Locarno. As such counts were not used for the whole series before 1947, it produced a strong inhomogeneity.
Our observers, among which very faithfull ones for more than 30 years, would probably tell you that they simply enjoy sunspot observing because: - it is one of the best ways to have a front-row view of the changing solar activity - it is not highly demanding: a few minutes per day at any time of the day is just what is needed to get this global count. Some of our observers do it even at their workplace, e.g. during the lunch break. Very flexible! - it is cheap: no costly camera or optics. Just a small telescope, a paper screen and your eyes are all you need.
Anyone can become member of our world wide observing network. We have both professional observatories(~30%) and amateur astronomers (~70%), from more than 30 different countries. As our current network is rather concentrated in Europe, we are particularly happy to welcome observers from other continents and latitudes.
The daily sunspot number is based on an average of all Wolf numbers reported during the 24h time bin of a UT day, i.e. between 0h00 and 24:00 UT. Therefore, the most logical time tag for each daily sunspot number is 12h00 UT.
The yearly average sunspot number is now obtained by taking the average of all daily numbers for the corresponding year. The result can thus be slightly different from a simple average of the 12 monthly mean values. Indeed, the months have different lengths. For years before 1849 and in particular before the 19th century, the yearly mean becomes more approximate. Indeed, when collecting past historical observations, R. Wolf had to derive monthly and yearly averages when sunspot counts were not available every day.
