This device, signed by Giovanni Battista Amici, served to move the eyepiece on the focal plane of the telescope by means of a slide and rack mechanism. The mount enabled the observer to explore the sky with controlled movements, or to track an object when it was escaping from view because of the apparent motion of the celestial sphere. The mount could also rotate on an axis parallel to the optical axis of the telescope so as to orient the eyepiece in the direction required by the observation.