Provided is a telescope (TSC) having: an objective optical system (OB); an erecting optical system (PR) for erecting an image formed by the Objective optical system (OB); and an eyepiece optical system (EP) for observing the image which is formed by the Objective optical system (0B) and erected by the erecting optical system (PR). The objective optical system (OB) includes, in order from an object, a first lens group (G1) having positive or negative refractive power, a second lens group (G2) having positive refractive power, and a third lens group (G3) having negative refractive power. The second lens group (G2) and the third lens group (G3) rotate together around a point (O) on the optical axis of the Objective optical system (OB) in order to correct the image.
