Le porte oculaire dois être précis et doux a manœuvrer

        Il existe le même en commerce mais très cher

                                                                                                                                                                                           La pièce jaune viens

                                                                                                                                                                                           en appuie sur la pièce

                                                                                                                                                                                           grise

                                                                                                                                                                                           La pièce grise et en

                                                                                                                                                                                           appuie sur les 4 roulem-

                                                                                                                                                                                           ments bleus

                                                                                                                                                                                           ça fonctionne par

                                                                                                                                                                                           frottements