IMPROVEMENTS IN REFRACTING AND REFLECTING TELESCOPES."
Year: 1854

page_text: LETTERS PATENT to Andrew Barclay, of Kilmarnock, in the County of
Ayr, North Britain, Engineer, for the Invention of "IMPROVEMENTS IN
REFRACTING AND REFLECTING TELESCOPES."
PROVISIONAL SPECIFICATION left by the said Andrew Barclay at the
Office of the Commissioners of Patents, with his Petition, on the
15th September 1854.
I, ANDREW BARCLAY, of Kilmarnock, in the County of Ayr, North Britain,
Engineer, do hereby declare the nature of the said Invention for "IMPROVE-
MENTS IN REFRACTING AND REFLECTING TELESCOPES" to be as follows:-
This Invention relates to the construction and arrangement of refracting
and reflecting telescopes. in such manner as greatly to increase their magnifying
capabilities, and enlarge their field of view.
The chief improvement in refracting telescopes consists in inserting an
intermediate lens or set of lenses between the object lens or lenses and
the lenses composing the eye-piece, in telescopes as ordinarily constructed.
For this intermediate lens or set of lenses, I prefer to use a double-concave
or a plano-concave lens or lenses, but other forms or combinations of lenses
may be used; and I fit this lens or lenses in a shifting tube or otherwise,
in such a manner that its position may be adjusted from the outside; or the
intermediate lens or lenses may be fixed, the eye-piece being made to shift,
037

page_text: as in ordinary telescopes. I use this intermediate lens or set of lenses in
combination either with an achromatic object glass, as ordinarily constructed,
or with a single double-convex lens, dispensing with the usual concave lens; or
with a single plano-convex or meniscus lens; or again, with two or more
double-convex, plano-convex. or meniscus lenses. placed one behind the other
at equal or unequal distances apart. In constructing reflecting telescopes,
I employ a large object lens or set of lenses, placing them at the mouth of the
instrument in front of the first reflector, the reflectors and the eye-piece being
arranged similarly to those in the telescope known as the Gregorian reflecting
telescope.
The use of the object lens or lenses is to concentrate or converge a much
greater amount of light upon the first reflector, and at the same time to
increase the magnifying capabilities of the instrument. The object glass may
consist of an achromatic lens, or of any of the arrangements of object lenses
herein-before described in reference to refracting telescopes.
These improvements are obviously applicable to all forms of reflecting
telescopes, and by them a compound magnifying power is obtained, as well as
an enlarged field of view.
According to another modification of these improvements, two or more
telescopes are arranged to bear on the same object, and are fitted with reflect-
ing or other apparatus for throwing the rays of light from all the telescopes
into one eye-piece, so as to combine the several images into one, and thereby
increase the amount of light which the eye receives.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Andrew Barclay in the Great Seal Patent Office on the
15th March 1855.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ANDREW
BARCLAY, of Kilmarnock, in the County of Ayr, North Britain, Engineer,
send greeting.
WHEREAS Iler most Excellent Majesty Queen Victoria, by ler Letters
Patent, bearing date the Fifteenth day of September, in the year of our
Lord One thousand eight hundred and fifty-four, in the eighteenth year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said Andrew Barclay, Her special license that I, the said Andrew
Barclay, my executors, administrators, and assigns, or such others as I,
the said Andrew Barclay, my executors, administrators, or assigns, should

page_text: at any time agree with, and no others, from time to time and at all times
thereafter during the term therein expressed, should and lawfully might make,
use, exercise, and vend, within the United Kingdom of Great Britain and
Ireland, the Channel Islands, and Isle of Man, an invention for "IMPROVE-
MENTS IN REFRACTING AND REFLECTING TELESCOPES," upon the condition (amongst
others) that I, the said Andrew Barclay, by an instrument in writing under
my hand and seal, should particularly describe and ascertain the nature of the
said Invention, and in what manner the same was to be performed, and cause
the same to be filed in the Great Seal Patent Oflice within six calendar
months next and immediately after the date of the said Letters Patent.
NOW KNOW YE, that 1, the said Andrew Barclay, do hereby declare the
nature of my said Invention, and in what manner the same is to be performed,
to be particularly described and ascertained in and by the following state-
ment, reference being had to the accompanying Drawings, and to the letters
and figures marked thereon, that is to say:--
My said Invention relates to the arrangement and construction of refract-
ing and reflecting telescopes, in such manner as to greatly increase their
magnifying capabilities, and enlarge their field of view.
And in order that my said Invention may be properly understood, I shall
now proceed to describe it, with the aid of the several explanatory Figures
on the Sheet of Drawings hereunto attached, such Figures indicating various
arrangements under which the improvements constituting my Invention may
be carried into effect.
Figures 1, 2, 3, 4, 5, and 6, on the Sheet of Drawings, are Diagrams indi-
cating the arrangements of six varieties of my improved refracting telescopes;
and Figures 7, 8. and 9. on the same Sheet of Drawings. are Diagrams
indicating the arrangements of three varieties of my improved reflecting
telescopes. One of my improvements in refracting telescopes consists in
inserting in them an intermediate lens, or an intermediate set or combination
of lenses. between the object lens or lenses and the lens or lenses composing the
eye-piece, comprehending under the term "eye-piece." any lenses such as are
used in ordinary telescopes for merely re-inverting the image, or for bringing it
into an erect position for being viewed by the actual or ultimate eye lens.
Various forms or combinations may be used for the intermediate lens or set of
lenses. In the arrangement delineated in Figure 1 of my Drawings, in which
Figure the object lens or set of lenses is at A. and the eye-piece consists of the
combination of lenses B, C, D. the intermediate lens is an achromatic plano-
concave lens E. In the arrangement delineated in Figure 2, in which the
object lens or set of lenses is at A, and the eye-piece consists of the lenses

page_text: B, C, D, an intermediate combination of lenses, composed of three achromatic
lenses E, F, G, is used. A similar arrangement of intermediate lenses E, F, G,
is delineated, in Figure 3, as in combination with a different arrangement of
eye-piece lenses B, C, D; and in Figure 4 is delineated a duplicate arrange-
ment of intermediate combinations of lenses E, F, G, and H, I, J, in combi-
nation with an eye-piece, composed of three achromatic lenses B, C, D, the
intermediate and eye-piece lenses constituting in fact three sets, each of three
achromatic lenses; 1 however prefer the arrangements delineated in Figures
5 and 6 of my Drawings. In the arrangement represented in Figure 5, I use
an achromatic object lens A, (or two achromatic object lenses may be adopted,
as in some of my other modifications.) and I place an achromatic lens B in the
focus of the object lens A. The best position for this lens B is in the actual
focal point of the object lens A, but it may be shifted a little either in advance
or backwards, without deteriorating the effect to any great extent; or two
such lenses may be placed, one slightly before the focus, and the other slightly
behind it. The lens B re-inverts the image inverted by the object lens A, and
it causes the centre rays C to converge. At the point of conveyance or
crossing of the rays C, I place an achromatic lens D, and behind this lens a
second achromatic lens E, these two lenses acting on the visual rays from the
lens B in much the same manner as the object lens A acts on the visual rays
direct from the actual object, and causing the formation of an image focus
at F, the distance of which depends on the proportions of the lenses B, D, E,
and may be made to suit the description of eye-piece lenses which the optician
wishes to employ. The eye-piece lenses in this arrangement consist of two
achromatic lenses G, H, which throw the several pencils of visual rays parallel,
so as to render the rays fit for vision. The arrangement represented in
Figure 6 differs from that shewn in Figure 5, in having an achromatic plano-
concave lens I, introduced between the object lens A and the re-inverting lens
B. This lens I causes the visual rays from the lens A to diverge or to pass on
in a less convergent direction, so as to form a larger image at the focus, in
which focus the lens B is placed, as before. The same letters indicate corre-
sponding parts in Figures 5 and 6. In some cases, and as is represented in
Figure 6, a single double-convex lens may be used instead of the two lenses
D, E. In the arrangements just described, in reference to Figures 5 and 6, 1
obtain a compound magnifying power, whilst at the same time a greater
amount of the visual rays are carried to the eye and rendered fit for vision, an
increased quantity of light being thus transmitted. In combination with the
arrangements of lenses which I have just described, I use either an ordinary
achromatic object lens, as represented in Figures 2, 3, 5, and 6, or I adopt a

page_text: combination of two or more achromatic lenses, as represented in Figures 1
and 4, by the use of which last-mentioned arrangement I obtain a rapid con-
vergence of the visual rays with. lenses of slight convexity, as compared with
the convexity of a single lens, for obtaining the same degree of convergent
effect upon the visual rays. The object lenses may be placed more or less
apart, but in all cases so that the second or succeeding lens or lenses shall be
in advance of the focal point of the front lens or lenses. Any of the known
arrangements of eye-piece lenses may be used in combination with my inter-
mediate lenses. The eye-piece represented in Figure 2, for example, is of the
description known as Huygen's eye-piece; I however prefer to form the eye-
piece by a combination of achromatic lenses, such as is represented under
different arrangements in Figures 1, 3, 4, 5, and 6. The necessary focal
adjustment in the refracting telescopes which I have herein described may be
effected in various ways. The intermediate lens or combination of lenses may
be carried by a separate moveable support inside the main telescope tube, and
it may be connected to an external adjusting screw, in the manner in which
the reversed mirror in reflecting telescopes is made adjustable; or the interme-
diate lens or lenses may be fixed in the eye-piece tube, so as to be moved and
adjusted along with the eye-piece; or again, the intermediate lens or lenses
may be fixed to the main tube of the telescope, the focal adjustment being
obtained by moving the eye-piece only.
My improvement in reflecting telescopes consists in using an object lens or
combination of lenses, which I place at the mouth of the instrument and in
front of the first reflector. According to one modification, which is indicated
in Figure 7 of my Drawings, and in which the object lens is at A, the first
reflector is a plane annular mirror B, and the visual rays which are made to
converge by the object lens A are reflected by the mirror B upon the central
and reversed mirror C, which also has a plane surface. The mirror C again
reflects the visual rays. which continue to converge after the reflections, and
reach a focus at D, passing thence through the central opening E in the
mirror B to the eye-piece at F. It will thus be seen that the space taken up
by the focal length of the object lens A is practically reduced to about one-
third of the space it would take up were the rays not reflected by the mirror
B and C, and in this manner a telescope of a given or determined power is
brought into a little more than one-third the usual length. In Figure 8 is
represented a combination of an object lens A with concave mirror B, C.
The visual rays converge after passing through the lens A, and this conver-
gence is increased by the concavity of the mirror B, so that in this instance
the rays form a focus, as at D, before reaching the mirror C. This mirror C

page_text: reflects the rays back through the central opening E in the mirror B to the
eye-piece at F. The arrangement represented in Figure 9 is designed to
obviate the loss of light caused by the interposition of the mirror C. To this
end the mirror B is set in an oblique position, so as to reflect the visual rays
to one side; and the reverse mirror C, which is also set obliquely, is placed in
such a position at one side as to receive the rays reflected by the mirror B, and
reflect them in a direction parallel to the axis of the main body of the telescope.
The arrangement of lenses herein-before described, in reference to Figures 5
and 6 of my Drawings, as applicable to refracting telescopes may also be
adapted to reflecting telescopes. As an example of this combination, the
reflecting telescope represented in Figure 9 is shewn with the arrangement
added to it. Here the lens b is placed in the focal point of the combination of
object lens and mirrors A, B, C, and in the crossing point of the central rays c
is placed the double-convex achromatic lens d, e. The image focus is at f,
and the visual rays are rendered fit for vision by the achromatic lenses g, h,
precisely as in the arrangements described in reference to Figures 5 and 6. It
is unnecessary for me to detail the proportions to be adopted in the various
lenses, as the practical optician will be able to ascertain these for himself, as is
done in regard to combinations of lenses already known and in use; but I may
remark that my Drawings indicate approximately the proportions which I
have found suitable, so far as my experiments have gone.
Another portion of my improvements consists in arranging two or more
telescopes to bear on the same object, and in fitting them with reflecting or
other apparatus for throwing the visual rays from all the telescopes into one
eye-piece, so as to combine the several images into one, and thereby increase
the amount of light which the eye receives.
Having now described and particularly ascertained the nature of my said
Invention, and the manner in which the same is or may be used or carried
into effect, I may observe, in conclusion, that I do not confine or restrict myself
to the precise details or arrangements which I have had occasion to describe or
refer to, as many variations may be made therefrom without deviating from the
principles or main features of my 'Invention: but what I consider to be novel
and original, and therefore claim as the Invention secured to me by the herein-
before in part recited Letters Patent, is, -
First, the general arrangement and construction of refracting and reflecting
telescopes, as herein-before described.
Second, the application and use in refracting telescopes of an intermediate
lens or combination of lenses inserted between the object lens or lenses and
the lens or lenses constituting the eye-piece, comprehending under the term

page_text: eye-piece "any lenses for merely re-inverting the image or for bringing it into
an erect position for being viewed by the actual or ultimate eye lens as used
in ordinary telescopes, as herein-before described.
Third, the system or mode of arranging and constructing refracting and
reflecting telescopes, wherein a lens or combination of lenses is placed in or
nearly in the first focus of the telescope, for the purpose of re-inverting the
image, as more particularly described in reference to Figures 5, 6, and 9 on
the Sheet of Drawings hereunto attached, such re-inverting lens or lenses
being used in combination with lenses such as are marked D, E, and d, e, in
the Figures referred to, for converging the visual rays to a second image
focus.
Fourth, the application and use in reflecting telescopes of an object lens or
lenses placed in front of the primary or first reflecting mirror, as herein-before
described.
In witness whereof. I. the said Andrew Barclay, have hereunto set my
hand and seal, this Thirteenth day of March, in the year of our Lord
One thousand eight hundred and fifty-five.
ANDREW BARCLAY. (L.S.)