How a sunspot number is calculated by an individual observer?

I would like to learn how to calculate the daily number of sunspots and where to get daily input images of the Sun.

I have read tens of web links and none mentioned or described any algorithm to work for the calculation of the sunspot number.


What is the number of sunspots in this paper plate drawing?




and still no hint and how numbering, encoding is assigned to individual sunspots in the paper plate drawing (as above).

  • 1
    $\begingroup$ Isnt there a guide for the formula.. k(10 g + s) where g is the number of sunspot regions, s is the number of spots, and k is a variable quantifying observing conditions and observer biases? $\endgroup$ Nov 1, 2022 at 22:51
  • 1
    $\begingroup$ @LifeInTheTrees since s is the number of spots, so how do you calculate that number ? Exactly what I was asking about. $\endgroup$
    – darius
    Nov 1, 2022 at 23:02
  • 1
    $\begingroup$ As far as I know, it’s the number of spots. The same thing as, e.g., the number of slices of pepper on a pizza. I count ≈ 35 in the drawing you link to, although it’s sometimes difficult to distinguish between two spots or a single large one that is “wasp-shaped.” $\endgroup$ Nov 2, 2022 at 0:22
  • 1
    $\begingroup$ @LifeInTheTrees you are right and I am ready to start with morphological analysis of sunspots. In the mean time I have visited 100+ websites STARA Project: STARA theses.gla.ac.uk/3429/1/2012watsonphd.pdf Glasgow Theses Service theses.gla.ac.uk [email protected] Watson, Fraser Thomas (2012) Investigating sunspot and photospheric magnetic field properties using automated solar feature detection. PhD thesis. theses.gla.ac.uk/3429 29. The STARA Sunspot Catalog Fraser Watson National Solar Observatory, Tucson, AZ 85719, USA $\endgroup$
    – darius
    Nov 3, 2022 at 21:43
  • 1
    $\begingroup$ 2. Sunspot Surface Calculation (Case Study on solving complex problems) V. codeproject.com/Articles/812896/… abandoned project since V. left institute I need to contact Chuck Bueter from Paper Plate Backyard Astronomy Project analyzer.depaul.edu/paperplate since his sunspots count is for real analyzer.depaul.edu/paperplate/images/Sun_trace_Clyde_zoomR.jpg He moved from project to project and hope to contact him via Facebook one day. Than I go to Japan: swc.nict.go.jp/en/trend/sunspot.html $\endgroup$
    – darius
    Nov 3, 2022 at 21:56


You must log in to answer this question.

Browse other questions tagged .