The Tetra ARmed Super-Ifu Spectrograph, TARSIS, is a new instrument to be placed in the 3.5m telescope in the observatory of Calar Alto, in Southern Spain. TARSIS aims to study galaxy clusters at redshift z∼0.15 in the near ultraviolet range. As the observations will take place on the ground, we need to study and quantify the extinction of the atmosphere in these wavelengths. This project focuses on taking and processing photometric observations of stars, reducing and analyzing the images to calculate the final contribution of the atmosphere and trying to establish a correlation between the extinction produced in the V and the NUV bands.