A microscope includes an optical imaging system with an adjustable corrector, a microscope drive, a position sensitive detector, an optical measuring system and a control unit. The optical measuring system configured to form first and second measuring light beams, direct the measuring light beams into an entrance pupil of the optical imaging system eccentrically with first and second distances to the optical axis thereof, receive first and second reflection light beams, and direct the reflection light beams onto the position sensitive detector. The control unit is configured to record positions of the reflection light beams on the position sensitive detector, and determine an aberration based on the recorded positions.