Improvements in and connected with Astronomical and other Telescopes.
Year: 1889

page_text: Date of Application, 4th Sept., 1889
Complete Specification Left, 19th Mar., 1890-Accepted, 19th Apr., 1890
PROVISIONAL SPECIFICATION.
Improvements in and connected with Astronomical and other
Telescopes.
1, ALFRED RUDALL M.A. of St. Agnes' Vicarage, Scorrier in the Duchy of
Cornwall Clerk in Holy Orders do hereby declare the nature of this invention to be
as follows:-
I make the reflectors of a concave curved surface formed by the revolution of that
part of the parabola which lies at the extremity of the parameter, round the axis
of the parabola, with the semi-parameter as its radius. Or the same effect may
practically be obtained by building the curve of the parabola of a series of very small
planes or sections of a sphere. The reflectors are made of plaster of Paris or of some
other similar material easily moulded into shape, and in the case of large reflectors
they may be built up in sections on some suitable backing or framework. The
reflector sections are each silvered separately before being fitted together.
In constructing an equatorial telescope, the paraboloidal reflector is enclosed in a
box of cubical or other convenient shape and forms the diagonal plane therein. This
box revolves on its horizontal axis in bearings of any suitable and stable construction
and means are provided for moving the box round on its axis.
This box is provided with two circular openings at adjacent sides one of them being
at the top and the other in the direction of the axis of rotation. On it is mounted
another similar box or framework containing an ordinary plane reflector set at right
angles to the main reflector in such manner that rays from the object to be examined
pass through a circular opening in the side of the box on to the plane reflector
whence they are reflected through a circular opening in the bottom of the box and
the upper opening on the lower box with which it coincides on to the paraboloidal
reflector which focusses them into the eye piece. The upper box is mounted on the
lower one in such manner as to be capable of rotating thereon on its vertical axis
relatively to the lower box, the axes of rotation of the two boxes being therefore at
right angles to each other and thus commanding the whole of the celestial hemisphere.
Each of the two exterior openings are provided with tubes of sufficient length to
exclude oblique rays.
The eye piece is always stationary being fixed at the proper distance according to
the focus of the parabola and is entirely independent of the reflector chambers.
For transit instruments I have no plane reflector, the parabolic reflector focusses
the rays direct into the eye piece which as before described is independently
fixed.
The reflector consists of a series of parabolic sections arranged in a vertical arc of
the same material and construction as before described; the portion of the parabola
used will vary with the relative position of the eye piece and the part of the heavens
in right ascension to he observed, but the central portion of the parabola, i.e. the
apex, the only part now used, is not used in these telescopes. The eye piece is
mounted in such manner as to revolve round the focus of the reflector, as its centre,
so enabling any portion of the parabolic arc to be examined.
For coast guard look outs and terrestial purposes generally the main reflector is
made of the usual form, that is, the central portion of the parabola is used, but the
mode of construction is the same as hereinbefore described. The secondary reflector
is plane of half the diameter of the main reflector, although under certain circum-
stances these proportions may be varied so that I am enabled to use a reflector of any
given focus in a shorter tube than usual.
1
2
1
1000
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.

page_text: COMPLETE SPECIFICATION.
Improvements in and connected with Astronomical and other
Telescopes.
I, ALFRED RUDALL M.A. of St. Agnes Vicarage Scorier, in the Duchy of
Cornwall, Clerk in Holy Orders, do hereby declare the nature of this invention and
in what manner the same is to be performed to be particularly described and
ascertained in and by the following statement :-
According to my invention make the reflectors of astronomical and other
telescopes of a concave curved surface formed by the revolution round the axis of
the parabola with the semi-parameter as its radius of that part of the parabola which
lies at or near the extremity of the parameter and my invention also consists in
improvements in the mode of building such reflectors and in the construction of
instruments suitable therefor. And in order that my invention may be more readily
understood I will describe the same with reference to the accompanying drawing of
which,
Figure 1 is a diagram representing a parabola.
Figure 2 is side elevation showing a convenient mode of mounting a reflector and
Figure 3 is a back view of reflector.
Figure 4 is side elevation of a telescope.
Figure 5 is the same partly in section."
Figure 6 is an end view of telescope with upper reflector box turned round a
quarter of a turn.
Figure 7 is side elevation of a telescope with a finder and shaped and covered so
as not to offer too much resistance to the wind.
Figure 8 is a side elevation partly in section of a transit instrument provided with
my improve reflector and
Figure 9 is a longitudinal sectional diagrammatic view of a look-out telescope.
Referring to Figure 1 which is a diagram representing a parabola I would have it
understood that utilize that part designated by a which lies at or near the extremity
of the parameter, instead of the part at or near the apex and designated by b which has
been the practice hitherto.
The reflectors are preferably made of plaster of Paris or of some other material
easily mou.ded into shape and in the case of large reflectors they may be built up
in sections on some suitable backing or framework. Or the same effect may
practically be obtained by building the curve of the parabola of a series of very small
planes or sections of a sphere. A convenient method of making the reflector or
sections thereof is as follows, a convex reflector-form or matrix made of iron or other
suitable material has a coating of silver deposited or laid thereon and a good backing
of copper is then deposited on the silver. The copper is then coated with a layer
of glue or some other adhesive, preferably cold, a coating of very fine plaster of Paris
and lastly a thick coat of rougher plaster. Furthermore a backing of wood or other
suitable material may if required be added. When set, the whole is removed from the
iron form or matrix and the silver surface is polished.
A convenient mode of mounting and adjusting the reflector or reflector-sections is
shown by Figures 2 and 3 in which y represents the reflector or a section thereof
mounted on a beams of wood or other suitable material by means of a screw 7 baving
a universal joint e or its equivalent at the end fixed to the back of the reflector y.
The reflector or reflector-section is eventually adjusted and fixed in its proper position
and at the proper angle by means of the set screws m and check nuts 2. The back
view Figure
shows back of reflector only and d are bearing plates for the set
screws m..
In constructing an equatorial telescope as shewn in Figures 4, 5 and 6, the
paraboloidal reflector y is enclosed in a box n of cubical or other convenient shape
and forms approximately the diagonal plane therein. This box n revolves on its axis
in bearings N or any other suitable and stable construction may be designed for that
purpose.

page_text: The box n is provided with two circular openings at adjacent sides, one of them being
at the top and the other in the direction of the axis of rotation. On it is mounted
another similar box or frame or framework o containing a plane reflector x set at
right angles to the reflector y in such manner that rays from the object to be
examined pass through a circular opening in the side of the box o on to the plane
reflector a whence they are reflected through a circular opening in the bottom of the
said box o and the upper opening on the lower box n, with which it coincides, on to
the paraboloidal reflector y, which focusses them into the eye piece 2, said eye piece
being suitably mounted at the proper distance from, and angle to, the paraboloidal
reflector y. Owing to want of space on the drawing the eye-piece is however shewn
in all cases much too close to the reflector y. The upper box o is mounted on the
lower one n in such manner as to be capable of rotating thereon on its vertical axis
relatively to the lower box, the axis of rotation of the two boxes being therefore at
right angles to each other and thus commanding the whole of the celestial hemisphere.
Each of the two exterior openings are provided with tubes o' and n of sufficient
length to exclude oblique rays. The lower box n is provided with a weight X to
counterbalance the weight of the upper box o.
A telescope of this construction inay be actuated in very much the same manner as
those at present in use for instance by applying motion with suitable releasing and
reversing gear to tooth wheels G and H. The wheel G is mounted on the trunnion
or pivot A of the lower box n whilst the movement of the upper box on the lower box
is provided for by the wheel H and wheel J mounted on a counter-shaft which at its
other end has another wheel F gearing with a spur wheel E and bevel wheel E'
which run loose on the shaft A. The wheels E and E' may be connected in any
convenient manner by clutches or the like and the wheel E¹ thus when desired
actuates bevel pinion d² mounted on a short shaft running in bearings d and having
at its other end a spur pinion c which latter gears with a circular tooth rim B on the
outside of the lower part of the upper box o. It is however evident that any
convenient arrangement of mechanism may be employed for actuating the several
moving parts of the instrument. In order to still further steady the apparatus I
provide the lower box n with a roller guide or guides ³ which moves or move on
pulleys n mounted in bearings on the bed-plate P. The boxes o and n have hinged
or sliding doors at their sides to facilitate easy access to their interiors for adjustment
and cleaning of the reflectors as shewn in Figure 4.
Figure 7 represents a telescope with a finder W, the upper and lower boxes being
covered or fashioned in such manner that they offer the least possible resistance to the
wind. o are handles on the upper box o, and p are handles on the lower box n so as
to facilitate turning the said boxes round by hand if desired.
The eye-piece z is always stationary being fixed at the proper distance according to
the focus of the parabola and is entirely independent of, and unconnected with, the
reflector chambers.
Although the telescopes have only been shown mounted in one position it is evident
that such may he varied according to the necessities of each case which would be
apparent to an astronomer.
The instruments which have just been described may also be used as transit
instruments. They may also be used as ordinary telescopes without apparatus of any
kind for moving the several parts except the handles o² and p or their equivalents.
Referring to Figure 8 it will be seen that for transit instruments I may dispense with
the plane reflector the paraboloidal reflector y focussing the rays directly into the
eye piece z which as before described is independently mounted. The eye piece in
this case however is capable of being moved in any direction round an imaginary
point B, which in the drawing is intended to represent the focus of the paraboloidal
reflector y constructed as before described. By moving the eye-piece z any part of
the reflector may be examined. The portion of the parabola used will vary with the
position of the eye-piece z and the part of the heavens in right ascension to be
observed but the central portion of the parabola (the apex), which is the only part

page_text: now used, is not used in astronomical instruments constructed according to my
invention.
For coast-guard look-outs and terrestrial purposes generally, the main reflector y
is, as shown in Figure 9, made of the usual forin, that is, the central portion of the
parabola is used, but the mode of construction of the reflector is the same as herein-
before described. The secondary reflector x which is of the same material and
construction is plane and of half the diameter of the main reflector, although under
certain circumstances these proportions may be varied so that I am enabled to use a
reflector of any given focus in a shorter tube than usual.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is
First. The employment and manufacture of reflectors, of which the curve is formed
of a part of a parabola, other than at or near the apex thereof.
Second. The method of building up reflectors by mounting parts or sections thereof
on a suitable framing.
Third. The manufacture of reflectors. or sections thereof in superposed layers by
coating or covering a matrix or form with a thin layer of silver, or other suitable
material, depositing a backing of copper or the like thereon and successively covering
this with an adhesive material such as glue and plaster of Paris of various degrees of
fineness or other substance for giving the desired solidity to the reflector removing
the latter from the matrix and finally polishing the silver surface substantially as
described.
Fourth. A telescope consisting of a fixed eye-piece za box or framework n mounted
on a trunnion or pivot A and containing a paraboloidal reflector y and another box or
frame work o having a plane reflector and suitable means for allowing the upper
box o to revolve on the lower box n, substantially as described and shown.
Fifth. A transit instrument consisting of a movable eye-piece and a paraboloidal
reflector substantially as described and shown.
Sixth. A look-out telescope consisting of an eye-piece, a paraboloidal reflector y of
ordinary form and a plane reflector x substantially as described and shown with
reference to Figure 9.
Seventh. The construction of reflectors or sections thereof as shown on the
drawing.
Eighth. The constructions of telescopes as shown on the drawings.
1000
day
of March 1890.
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.