Fraser Watson

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STARA
Sunspot Tracking And Recognition Algorithm



This algorithm works on level 1.5 continuum data from the SOHO MDI instrument and automatically detects and tracks sunspots as they move with the solar rotation.

A FITS file is inverted and then a top-hat transform is taken which essentially flattens the background leaving the sunspot intensity peaks intact. This produces a list of detected sunspots along with various physical properties such as their area and 'centre of mass' locations. The various sunspot detections are then corrected for solar rotation and compared with sunspot locations in subsequent images to allow the evolution of physical parameters to be studied.

The STARA code was provided to researchers at Kanzelhohe Observatory in Austria where it is used as a guide for sunspot detections in their daily solar observations (see Kanzelhohe Observatory for more details).

Relevant publications

Automated sunspot detection and the evolution of sunspot magnetic fields during solar cycle 23
F. T. Watson, L. Fletcher and S. Marshall (submitted)

Modeling the longitudinal asymmtery in sunspot emergence - the role of the Wilson depression
F. T. Watson, L. Fletcher, S. Dalla and S. Marshall (2009)
Solar Physics, 260, p5 (arXiv link)