Optical system for tracking and visually examining a target, comprising an image sensor and a lens arrangement having a variable position relative to the image sensor to project an image of the target onto the image sensor, a light source for emitting light in a predetermined wavelength range in the direction of the target and a filter switch for switching an optical filter for selectively allowing the light in the predetermined wavelength range to pass through to the image sensor into and out of the optical path to optionally perform a visual examination and monitoring of the tracking. A tracking device is provided to perform the tracking of the target using the reflected light in the predetermined wavelength range in a sequence of images held by the image sensor when the first optical filter is switched into the optical path.