Field of view around HD 172555 showing only background stars with their CHEOPS triangular PSF. East is downward and north is leftward. Gaia identified objects are indicated as red circles and the large black circle represents the optimal aperture of CHEOPS with a size of 25″. Apart from HD 172555, the three closest objects within the aperture have G magnitudes of 18.5, 15, and 20 in order of increasing distance from the centre of the aperture. The brightest object in the east is the M-dwarf companion CD-64 1208 with G = 8.9 mag.