Abstract
A great sunspot group of October 1991 (NOAA 6891 atL = 189,B = −10) was observed, in which an eruptive flare of importance (X2.5/31B) has been reported. A Caii-line 3933 A filter was used, and during a time interval of 3 hours more than 90 frames were taken, using a CCD camera. The progress and the distribution in size of the two main flare points have been obtained; they covered an area of about 1800 millionths of the solar disk within a time interval of about 24 min. The average apparent horizontal velocity was 70 km s−1.
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