Abstract: The polar-axis telescope has an objective lens, a focal plate, an eyepiece, a zoom optical system, and a zoom optical system driver. The objective lens forms an object image, and the focal plate is arranged on a focal plane of the objective lens. The eyepiece is arranged backward of the focal plate and forms an observed image. The zoom optical system is arranged between the objective lens and the eyepiece. The zoom optical system makes the observed image appear gradually bigger while maintaining an in-focus situation. The zoom optical system driver shifts the zoom optical system along a polar-axis, corresponding to an optical axis of the polar-axis telescope, so as to change a magnification.

Abstract: The polar-axis telescope has an objective lens, a focal plate, an eyepiece, a zoom optical system, and a zoom optical system driver. The objective lens forms an object image, and the focal plate is arranged on a focal plane of the objective lens. The eyepiece is arranged backward of the focal plate and forms an observed image. The zoom optical system is arranged between the objective lens and the eyepiece. The zoom optical system makes the observed image appear gradually bigger while maintaining an in-focus situation. The zoom optical system driver shifts the zoom optical system along a polar-axis, corresponding to an optical axis of the polar-axis telescope, so as to change a magnification.

Abstract: An eyepiece attachment structure for attaching an eyepiece to an observation optical instrument is provided with an attaching sleeve protruding from the eyepiece, a holding member secured to the body, the holding member frictionally holding the attaching sleeve when the attaching sleeve is inserted in the observation optical instrument, and a rotation preventing mechanism that mechanically prevents rotation of the attaching sleeve relative to the holding device when the attaching sleeve is inserted into the observation optical instrument.

Abstract: A mounting base which includes an object side portion, an eyepiece side portion, and a connecting portion. The connecting portion connects the side portions, and the side portions are parallel. A pair of first mounting holes are formed in the object side portion and a pair of second mounting holes are formed in the eyepiece side portion. An axis line, perpendicular to the object side portion, which goes through a geometric center of gravity of one of the first mounting holes is coaxial with an axis line, perpendicular to the eyepiece side portion, which goes through a geometric center of gravity of one of the second mounting holes. Lens barrels of the objective lenses are fixed to the first mounting holes. Eyepiece units, in which the eyepieces are held, are rotatably engaged with the second mounting holes.

Abstract: A connecting member is provided with a first, a second and a third arm which radially extend. A first hole is formed at an end of the first arm, and a second hole is formed at an end of the second arm. The centers of the first and second holes respectively coincide with optical axes of objective lenses. A pair of eyepiece groups are held by a pair of holders. The holders are rotatably held by the first and second holes, so that an interpupillary adjustment is carried out. A rotation ring axle is threadably engaged with a third hole formed at an end of the third arm. A guide shaft passes through a junction of the first, second and third arms. The connecting member is movable along optical axes of the eyepieces, so that a focusing operation is carried out.

Abstract: An eyepiece attachment structure for attaching an eyepiece to an observation optical instrument is provided with an attaching sleeve protruding from the eyepiece, a holding member secured to the body, the holding member frictionally holding the attaching sleeve when the attaching sleeve is inserted in the observation optical instrument, and a rotation preventing mechanism that mechanically prevents rotation of the attaching sleeve relative to the holding device when the attaching sleeve is inserted into the observation optical instrument.