A new method is described for simulating charged particle rays in arbitrary electrostatic lens systems of cylindrical symmetry. The method is so efficient (<4 ms/step) that even for complex lens systems the trajectories can be computed and displayed during the lens voltage adjustment, using the same laboratory microcomputer which controls the lens voltages. The time lag between a change of a lens element voltage and the trajectory display is of the order of a few seconds for long, multielement lens systems. This also allows one to optimize the voltage combinations by performing trajectory calculations for many lens voltage settings. The performance is demonstrated by comparing with recent experimental data of Heddle and co‐workers on imaging properties of a three‐element tube lens. As an application of the fast computation time feature, trajectories and voltages are shown for a lens system providing an electron optically adjustable angle resolution as used in a spin polarized photoemission experiment with synchrotron radiation.