7-draw English telescope by Dudley Adams –
7-draw portable achromatic terrestrial telescope by Dudley Adams, one of
the foremost opticians at the turn of the 18th 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