An optical system for a microscope for imaging an object includes: a telescope system having an optical correction unit, which is adjustable in order to correct a spherical imaging aberration, and having a zoom optical unit, which is adjustable in order to adapt a magnification of the telescope system to a ratio of two refractive indices, one of which is assigned to an object side and an other of which is assigned to an image side, within a predetermined magnification range. The telescope system is telecentric over an entire magnification range both with respect to the object side and with respect to the image side by the zoom optical unit contained in the telescope system.