High-Resolution Photography of the Solar Chromosphere. XIV: Morphology of Sunspots at the Chromospheric Level
A detailed description is given of the morphology of two isolated, fairly regular sunspots based on high-resolution observations obtained at seven wavelengths in the Hα line with a spectral purity and discrimination not hitherto achieved. Photometric traces across one of the spots confirm an earlier conclusion that the umbra-penumbra boundary is diffuse near the line centre but sharp in the wings. They also reveal considerable changes in the intensity contours of a sunspot from line centre to wings.