A method for mass analyzing multiply-charged ions is provided as well as a mass analyzer suitable for performing the method, the method comprising: introducing multiply-charged ions into an electrostatic mass analyzer where ions undergo multiple changes of direction of motion; detecting the ions in the analyzer; and determining the mass-to-charge ratio of at least some of the detected ions; wherein the absolute velocity in the analyzer of at least some of the ions whose mass-to-charge ratio is determined is not greater than 8,000 m/s and the average path length over the duration of detection of such ions is longer than required for detecting such ions with a mass-to-charge ratio resolving power of 1,000. High resolution mass spectra of high m/z protein complexes, for example in a native state and with low charge, can be achieved.