A remarkable 7-draw portable achromatic terrestrial telescope by Dudley Adams, one of the foremost opticians at the turn of the 18^th century.  The telescope measures 20” when fully extended, and only 4 5/8” when closed.  The main lens is 1 1/2” in diameter.   The front tube is mahogany in fine condition, while the body is German silver – a mixture of copper, nickel, and zinc -- that may be used here for the first time. The eyepiece draw is signed, “Adams’s New Patent Portable Telescope, No. 60 Fleet St, London.”   Adams worked at this address between 1796 and 1826, which helps date the instrument to circa 1820.  The “Patent” referred to is the way in which Adams maintains the constant ratio between the lens elements of the eyepiece and erecting lenses as the draws tubes are opened and closed. His ingenious invention made it possible to collapse a telescope to a very portable size.  The optical system is excellent, delivering a sharp image of good contrast.  The highly innovative portable optical system, coupled with the early use of German silver make this an important telescope from a very important maker. 

Item 5030...................sold