Japanese 22.5 + 30 x 180 mm Binoculars
A 180 mm version with Cooke f4.5 triple element objectives and double turret oculars providing 22.5 x and 30 x was produced in small quantities. The real fields are 2.6 and 2 degrees, respectively. Both the 150 mm and 180 mm instruments have Porro Il prism systems. The 60, 80, 105, 120 and several 150 mm instruments are collimated by adjustable eccentric objective rings. In other 150 mm and in the 180 mm models, collimation is achieved by prism adjustment. Without fixtures this can be, and usually is, a very tedious affair. The larger versions can be quite heavy. Depending on the design, the 120 mm can weigh from 30 to 50 pounds without mountings. The 150 mm can weigh 80 pounds and the 180 mm can tip the scales at 130 pounds - not recommended for a bird watching expedition. One hundred and thirty pounds is not in itself very heavy, but these instruments do not have many hand holds and the alarming possibility exists of dropping such a rare specimen. To my knowledge, the 150 mm and 180 mm models were not produced in inclined eyepiece versions.