The importance of visual counting (PLEASE READ)

American Association of Variable Star Observers (AAVSO)
Fri, 02/03/2023 - 21:49

“Although visual counting of spots may sound archaic in comparison with the many advanced modern solar data collected by ground-based observing networks and space missions (25- year old SoHO, SDO, Parker Probe, Solar Orbiter), they remain our sole link to the distant past. In order to put this detailed but mostly very recent solar knowledge in a temporal perspective, it must be attached to a long-term standard. We need to be able to answer the question: is the Sun, as we observe it today, equivalent and representative of the state of the Sun several centuries or millennia in the past and in the future? Therefore, today, we need to continue this heritage series in parallel with all other techniques, in order to calibrate the relation between various solar parameters (spectral irradiance, solar wind flux, global magnetic fields) and the sunspot number, and this over/ the whole range of possible activity regimes (See for example Kopp et al 2016). This means that we must continue for at least one or more solar cycles" (Clette 20-1)

The bottom line is that solar scientists need reliable visual observations that are done in a way that is consistent with the way observations have been done for nearly two centuries. Through the use of k-factors and other statistical analysis we can turn what one might consider the problem of variance in human interpretations into a solid, reliable timeline of solar activity. 

The AAVSO exists to help observers collect scientifically useful data on variable stars, including the sun, and house that data in a historically robust database for the use of the scientific community. This has been our mission for more than a century. It is an amazing honor and responsibility to be involved in the process of making sure that our database remains a gold standard. 

We therefore respectfully request that all observers follow the posted observing procedures of the solar section; this includes the submission of visual white light observations via either the filtered or projected image of the sun as seen with the observer's telescope (not an online image or a photograph or CCD or CMOS or DSLR or any other non human eyeball technology). Following this procedure will keep your observations scientifically useful as part of the AAVSO solar database. 

Many thanks to each and every observer who has submitted data to us, whether you have submitted 10 or 10,000 observations. Every data point is valuable. 


LKR, aka Dr. Kristine Larsen, Professor of Astronomy, Central Connecticut State University, Past President of the AAVSO, co-leader of the AAVSO Solar Observing Section



Clette, Frédéric (2021) The Sunspot Number: Reconstructing the Past Solar Cycle for the Future. Space Research Today 210: 10-23.