Purple Mountain Observatory
Nanjing, Jiangsu, PRC

9. Great Sunspot Group

This is photograph taken with the Purple Mountain Observatory 20 cm aperture refracting telescope on July 15, 1980. The granulation on the disc of the sun is very distinct. The umbra and penumbra of the sunspot area also very clear. The total area of the group is 1,315 solar disc unit (1 unit is equal one millionth of sun's disc are). The size of the biggest sunspot on the right is equal to 4 times the earth's diameter.