Focal plane deformation for the two CONCERTO arrays. The top panels present the focal plane distribution of the valid kids for the 2021 and 2022 kid sweep parameters, in Cassegrain offsets coordinates, with the LF and HF array on the left and right panels, respectively. Overall the FoV is enclosed by a circle with a diameter of 18.54′ represented as a solid black line. The bottom panel shows the deformation between the constructed offset and the recovered positions in the sky. The underlying black arrows show the fitted two-dimensional polynomial of degree 4 used to match the two positions. A main deformation mode is common to both LF and HF arrays.