The eight main steps in the formation of the full 2D PSF for a source in a given instrument, of a given energy and at a given off-axis and azimuthal angle: the King (beta2d) component [1] is constructed, then the Gaussian (gaus2d) core [2] is constructed, and these are added [3] in the correct ratio (the CCF parameters in steps 1−3 are all functions of instrument, energy and off-axis angle). Then this is rotated [4] according to the azimuthal position of the source on the detector, and only then are the radially-dependent primary [5] and secondary [6] spoke structures azimuthally filtered in, using a flat-topped triangular function. Finally, the large-scale azimuthal modulation (a function of EPIC instrument) is filtered in [7], and the very light radially-dependent smoothing applied [8]. The example shown is for MOS2, at an energy of 1.5 keV, an off-axis angle of 9′, and a source azimuthal position of 30°.