An apparatus for adjusting a viewing angle of a microscope is disclosed. In a preferred embodiment thereof, a bent eyepiece tube includes a prism on a first optical axis thereof for redirecting an object image to a second optical axis of the tube on which a magnifying eyepiece is aligned. The eyepiece tube is mounted on the microscope for rotation about the first optical axis by a collar, and a spring plunger carried by the tube is biased for respective engagement with a pair of opposing recesses in the collar to releasably secure the eyepiece tube in predetermined rotational positions corresponding to a pair of different viewing angles.