Cover Caption

The Fourier transform of a 64 mrad diameter patch from a simulated electron Ronchigram of 4 nm thick strontium titanate [100]. Defocus = −600 nm, spherical aberration = 0.1 mm at 300 kV. For a large patch, the positions of the heads of the comet-like spots depend on the sample and primarily the low-order aberrations (such as defocus), while the tails depend on higher-order aberrations.