Operating knob for an optical system

An operating knob for an optical system comprises:

• a first and a second coaxially arranged rotating element, wherein the first and the second rotating element are independently rotatable, the first rotating element rests against the optical system, the second rotating element is arranged downstream of the first rotating element, the first and the second rotating element have at least partly conical form, and that the first rotating element has one side directly opposing the second rotating element and has a larger maximum diameter than the second rotating element and a step is formed at the side of the second rotating element directly opposing the first rotating element, wherein the step possesses a diameter which is approximately the diameter of the first rotating element close to the second conical rotating element and wherein the first conical rotating element has a maximum diameter (D1) close to the optical system from 57.0 to 63.0 mm, and a diameter (D2) close to the second conical rotating element from 51.5 to 56.5 mm and wherein the second conical rotating element has a maximum diameter (D3) close to the first conical rotating element from 34.0 to 38.0 mm and close to a front end from 29.3 to 33.3 mm.