S/N = 5 detection limit of our AstraLux observation of CVSO 30 (Fig. 7). The reached magnitude difference that is dependent on the angular separation to the star is shown. The horizontal dashed lines indicate the expected magnitude differences of sub-stellar companions of the star at an age of 3 Myr. Beyond about 1.8 arcsec (or ~640 au of projected separation), all companions with masses down to 10 M_Jup can be excluded around CVSO 30.