Using the principle of normal telescopes, in the 18^th century, lenses were encased in wooden, vellum or leather tubes held together with brass fittings. Obviously most of them were too large in size and unwieldy and in general uncomfortable. However, the march of progress made it possible for the entire telescope to be made up of brass and not wood and vellum and in general a lot of other things. The problem was that science had not yet progressed so far as to make them smaller and portable to use. Even the brass telescope wasn’t suitable for use. The size closed or opened posed a serious problem as well as the length of the thing. The brass telescope even had to sacrifice its field of vision because of its size and weight, about 15 inches radial. 

However, during this time there was also the wonderful invention of the night-vision telescopes. These came equipped with a larger objective lens so that inverted images can be produced, but during the production of the proper image, the extra light could not be reabsorbed by the refracting lens itself. 

The technology that created and made nautical telescopes indispensable for sea voyages, moved on eventually and made way for more portable technology such as binoculars, which made it easier for people to use and had the same function as a nautical telescope until its use declined and eventually it had no use on a ship anymore. 

Now, nautical telescopes find home in museums and in private collections as a reminder of the past and of its people. From an important piece of equipment it has been reduced to a mere collectible to be coveted by people from all over the world. Maritime Museum on the Atlantic in Nova Scotia and National Maritime Museum in UK house some of the best collections of nautical telescopes while preserving their nautical heritage.