College of Science;
China Three Gorges University;
Yichang 443002;
China;
Yunnan Observatories;
Chinese Academy of Sciences;
Kunming 650216;
China;
National Astronomical Observatories;
Chinese Academy of Sciences;
Beijing 100101;
China;
Chongqing University of Arts and Sciences;
Chongqing 402160;
China;
sunspots; methods:data; analysis; techniques:image; processing;