Kodaikanal Solar Observatory (KoSO) White-Light Sunspot Regions Masks (1904-2017)

Regular observations at the Kodaikanal Solar Observatory (KoSO) began in 1904 using a white-light telescope with a 10-cm aperture lens and an f/15 light beam. Between 1912 and 1917, the objective lens was changed several times. In 1918, a 15-cm achromatic lens was installed. This new configuration produced a 20.4 cm size image of the Sun in the image plane. Photographic plates were used to capture the image. The same telescope has been used since 1918 up until 2017 to take regular white-light observations of the Sun. This data set provides the sunspot mask in HDF5 format for all the White Light Observations acquired at KoSO. Each HDF5 file contains the sunspot mask for all the observations for that year. The sunspot masks are provided in two different coordinate systems: (i) Full Disk as observed and (ii) Carrington heliographic coordinate, which is transformed from full disk using near point interpolation. Each data set also contains metadata in the form of HDF5 attributes. The Carrington co-ordinate data if full Sun map, hence the near-side  of the Sun is the region where values in the mask in non-zero, where as sunspot regions are filled with value 2. 

A Python package (KoSOpy), which can be located on GitHub, is being developed which can be used to navigate through these data sets.