Antique Monocular Nautical Brass Binocular Telescope for Bird Watching Camping Vintage Spyglass Collectible Brass Marine Binocular Sailor Instrument

Almost From The Invention Of The Telescope In The 17Th Century The Advantages Of Mounting Two Of Them Side By Side For Binocular Vision Seems To Have Been Explored. Most Early Binoculars Used Galilean Optics; That Is, They Used A Convex Objective And A Concave Eyepiece Lens. The Galilean Design Has The Advantage Of Presenting An Erect Image But Has A Narrow Field Of View And Is Not Capable Of Very High Magnification. This Type Of Construction Is Still Used In Very Cheap Models And In Opera Glasses Or Theater Glasses. The Galilean Design Is Also Used In Low Magnification Binocular Surgical And Jewelers' Loupes Because They Can Be Very Short And Produce An Upright Image Without Extra Or Unusual Erecting Optics, Reducing Expense And Overall Weight. They Also Have Large Exit Pupils, Making Centering Less Critical, And The Narrow Field Of View Works Well In Those Applications. These Are Typically Mounted On An Eyeglass Frame Or Custom-Fit Onto Eyeglasses. Binoculars Using Roof Prisms May Have Appeared As Early As The 1870S In A Design By Achille Victor Emile Daubresse. In 1897 Moritz Hensoldt Began Marketing Roof Prism Binoculars.