TY  - GEN
A1  - Diercke, Andrea
A1  - Arlt, Rainer
A1  - Denker, Carsten
T1  - Digitization of  Spörer’s sunspot drawings
T2  - Postprints der Universität Potsdam : Mathematisch Naturwissenschaftliche Reihe
N2  - 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.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 577 
KW  - sun: sunspots
KW  - sun: photosphere
KW  - sun: activity
KW  - techniques: image processing
KW  - astronomical databases: miscellaneous
KW  - history and philosophy of astronomy
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-413922
SN  - 1866-8372
IS  - 577
SP  - 63
EP  - 64
ER  -