Example of the PSF star selection panel provided by the software. For each candidate star, the interface displays its 20 × 20 pixels image alongside its light profile, also in 20 pixels (even if the PSF fitting radius is fewer than 10 pixels). Each line in the profile represents a line crossing through the star center, with consecutive lines corresponding to rotated profiles at different angles. The solid line indicates the averaged profile, which ideally approximates a Gaussian shape. Ideally one rejects the profiles which have contamination of near sources in the inner user selected fitting radius.