Purtroppo, questa descrizione non è stato tradotto in italiano, in modo da trovare a questo punto una descrizione inglese.
Dobsonian telescopes need to be finely balanced along the vertical axis. If the object placed in the centre of your eyepiece leaves the visual field as soon as you let go of the tube, no proper observation is possible. Normally this is not a problem as the telescopes are designed to remain balanced. But when you attach heavy accessories to the focuser, e.g. a high quality eyepiece, a pair of binoculars or a large finderscope, the telescope can become “top heavy”.
Additional weights can bring your Dobsonian back into balance.