Representative PSFs for the cameras of the northern station, taken from the 6.4 s exposures made by the cameras on July 7 2016 23:42:16 UT. Stars with 6 <m_V< 7 were selected close to the points of a 3 × 3 grid across the CCD with coordinates at , and the size of the image in both x and y. The colour scale of each PSF was adjusted to run from −3 to 9 times the standard deviation on the local background. Near the centre (column ) the PSFs are symmetric, whereas toward the edges they are distorted by varying degrees of coma that are introduced by the optics.