IMPROVEMENTS IN TELESCOPES
Year: 1876

page_text: LETTERS PATENT to John Lyon Field, of Manor House, Broadwater, in the
County of Sussex, Gentleman, for the Invention of "IMPROVEMENTS IN
TELESCOPES."
Sealed the 1st September 1876, and dated the 20th May 1876.
PROVISIONAL SPECIFICATION left by the said John Lyon Field at the Office
of the Commissioners of Patents on the 20th May 1876.
JOHN LYON FIELD, of Manor House, Broadwater, in the County of Sussex
Gentleman. "IMPROVEMENTS IN TELESCOPES."
This Invention has for its object improvements in telescopes.
In ordinary hand telescopes much inconvenience arises in adjusting the focus
owing to the friction of the parts, which results from the necessarily accurate fit
of the "draws" or tubes one within another; sometimes when only a slight expan-
sion or contraction is needed the force that has to be exerted to overcome the
friction of the draws or tubes results in the jerking or moving through a greater
distance than is required of the draw or tube to be adjusted.
Now my Invention is designed to obviate this inconvenience. For this purposo
I construct the ordinary hand telescope with a swivelling or revolving eye plate or
steadier so arranged that the last draw or tube which contains the crector and cyc
piece may be rotated without turning the eye plate or steadier which rests against
the user's eyebrow or face.
Between some two of the draws or tubes, preferably between the last draw or tube
and that into which it takes, I interpose an intermediate tube cut or formed with a
helix or worın. This tube fits on the one draw or tube of the telescope, and the
helix or worm receives a pin or piece projecting from the adjacent draw or tube.
Thus by turning the intermediate tube the final adjustment of the telescope to suit
the user may be readily effected with the greatest nicety.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Lyon Field in the Great Seal Patent Office on the 17th November
1876.
JOHN LYON FIELD, of Upper Norwood, in the County of Surrey, late of Manor
"IMPROVEMENTS IN
House, Broadwater, in the County of Sussex, Gentleinan.
TELESCOPES."
This Invention has for its object improvements in telescopes.
In ordinary hand telescopes much inconvenienco arises in adjusting the focus
owing to the friction of the parts, which results from the necessarily accurate
fit of the "draws" or tubes one within another; sometimes when only a slight
clongation or contraction is needed the force that has to be exerted to overcome
the friction of the draws or tubes results in the jerking or moving through a
greater distance than is required of the draw or tube to be adjusted.
Now my Invention is designed to obviate this inconvenience. For this purpose
I construct the ordinary hand telescope with a swivel or revolvable eye plate or
steadier so arranged that the last draw or tubo which contains the erector and eye
piece may be rotated without turning the eye plate or steadier, which rests against
the user's eyebrow or face and serves as a shield from the surrounding light.
Btween some two of the draws or tubes, preferably between the last draw or tube
and that into which it takes, I interpose an intermediate tube cut or formed with a
helix or worm. This tube fits on the one draw or tube of the telescope, and the
helix or worm receives a pin or piece projecting from the adjacent draw or tube.
Thus by turning the intermediato tube the final adjustment of the telescope to
suit the user may be readily effected with the greatest nicety.
The accompanying Drawing shows a telescope embodying my Invention, the
view being a central longitudinal section with part of the intermediate tube in
full to better shew the helix or worm.
b
The last
is the body of the telescope, 6 the first draw, c the second draw, and d the
third or last draw, provided with a swivel or revolvable eye plate c.
draw d is made adjustable by the interposition between it and the draw c of an
intermediate tube f, one end of which is screwed as usual to receive the slide
piece of the last draw (d). The draw d slides somewhat stiffly in its slide piece g.
On the other end of the intermediate tube f is cut or formed a helix or worm h
fitting freely but nicely in the draw c. The front end of the tube f is also reduced
in diameter below that of the body of the screw h for the purpose of forming a
shoulder. Against the stop ring i of the draw ca pink (or it may be a helical
piece) securely fixed in or to the draw c takes into the helix or worm h, thus the
draw c in conjunction with the pin (or helical piece) acts relatively to the inter-
mediate tube f in the manner of a nut, within which the helix or worm h freely
moves in a combined rotary and longitudinal senso.
The action is as follows:-Assuming all the draws to be tolerably stiff, the
body a of the telescope is held in one hand whilst with the other hand the user
pulls out the draws to the full extent, which involves no judgment or nicety of
adjustment. Then the eye plate is placed up to the eye, and whilst the body a
is still held by the one hand the focus is easily adjusted by simply rotating the last
draw d either to the right or left, as the case may be, by the other hand.
Having described the nature of my said Invention, and explained in what
manner the same is to be or may be performed or carried into practical effect, I
hereby declare that what I consider to be novel and original, and therefore clnim
as the Invention secured to me by the herein-before in part recited Letters
Patent is-
The making the focus of the ordinary hand telescope adjustable by the turning
of one of the draws, substantially as described and shewn.
I also claim in conjunction with the arrangement for adjusting the focus by the

page_text: turning of one draw, the application and use of the swivel or revolvable eye plate
or stendier c, as shewn.
In witness whereof, I, the said John Lyon Field, have hereunto set my hand
and seal, this Seventeenth day of November, in the year of our Lord One
thousand eight hundred and seventy-six.
JOHN LYON FIELD. (L.S.)