Fastening device for an aiming telescope on a weapon

A fastening device for attaching an aiming telescope (1) on a weapon using a mounting rail (2) connected to a telescope housing and extending along the telescope, the mounting rail being supported on at least one mounting apparatus (3a, 3b) fastened to the weapon. The mounting rail is provided with a longitudinal groove (5) and a clamping part (7) corresponding to an inside profile of the longitudinal groove (5) is inserted into the groove and fixed with an attaching screw (8) that engages threads (9) in the clamping part (7). The attaching screw (8) is passed through an opening (11a, 11b) in the mounting apparatus (3a, 3b). The mounting rail (2) is provided on the side facing the mounting apparatus (3a, 3b) with a toothing (22) that is engaged by at least one projection (23) protruding from the mounting apparatus.