An optical device for viewing an object at a range of working distances. The device comprises a slender tube of a certain length and having a distal end and a proximal end. The device farther comprises an imaging system disposed at the distal end and having a wide viewing angle. The device also comprises a telescopic system associated with the proximal end and having a narrow viewing angle. The imaging system is designed to form an image of the object at an image plane located on the device's optical axis and within the tube closer to the distal end than to the proximal end. The telescopic system is designed to enable viewing of the image of the object. The device is especially adapted to function as an endoscope in medical applications and may be disposable.