A study of the contrast of sunspots from photometric images

The thermal contrast alpha, and the umbra-penumbra A(u)/A(p) were calculated for 63 sunspots of various sizes and morphologies. Results show that values of alpha ranged from 0.1807 to 0.4266 and A(u)/A(p) ranged from 0.0089 to 0.4899. The values of thermal contrast and umbra-penumbra were compared with complexity ratings, magnetic field strength, and time factors and found to be independent of these parameters.