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Digitization of Spörer's sunspot drawings

Published online by Cambridge University Press:  18 July 2013

Andrea Diercke
Affiliation:
Leibniz-Institut für Astrophysik Potsdam, 14482 Potsdam, Germany email: adiercke@aip.de Institut für Physik und Astronomie, Universität Potsdam, 14476 Potsdam, Germany
Rainer Arlt
Affiliation:
Leibniz-Institut für Astrophysik Potsdam, 14482 Potsdam, Germany email: adiercke@aip.de
Carsten Denker
Affiliation:
Leibniz-Institut für Astrophysik Potsdam, 14482 Potsdam, Germany email: adiercke@aip.de
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Abstract

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Much of our knowledge about the solar dynamo is based on sunspot observations. It is thus desirable to extend the set of positional and morphological data of sunspots into the past. Gustav Spörer observed in Germany from Anklam (1861–1873) and Potsdam (1874–1894). He left detailed prints of sunspot groups, which we digitized and processed to mitigate artifacts left in the print by the passage of time. After careful geometrical correction, the sunspot data are now available as synoptic charts for almost 450 solar rotation periods. Individual sunspot positions can thus be precisely determined and spot areas can be accurately measured using morphological image processing techniques. These methods also allow us to determine tilt angles of active regions (Joy's law) and to assess the complexity of an active region.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2013 

References

Spörer, G., 1874, Pub. Astron. Ges. 13Google Scholar
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Gonzalez, R. C. & Woods, R. E., 2002, Digital Image Processing, Prentice-Hall, NJ Google Scholar