A charged particle apparatus is equipped with a third stigmator positioned between the objective lens and a detector system, as a result of which a third degree of freedom is created for reducing the linear distortion. Further, a method of using said three stigmators, comprises exciting the first stigmator to reduce astigmatism when imaging the sample, exciting the second stigmator to reduce astigmatism when imaging the diffraction plane, and exciting the third stigmator to reduce the linear distortion.