The dataset consist of camera shots of the sky. The camera - a total sky imager manufactured by Canon (Powershot) - was mounted at the top of the Research Vessel Polarstern. At the leg4 (from June until August 2020) of the MOSAIC experiment from Longyearbyen - Arctic Ocean this camera shots were taken with a temporal resolution between 1 minute and 16 seconds. The dataset represents the visible projection of weather conditions and cloud cover recorded on the vessel Polarstern in the direction near the zenith. These observations are useful for the interpretation of the atmospheric radiation measurements.