Improvements in Apparatus for Rotating Telescopes for Astronomical and other Purposes.
Year: 1895

page_text: Date of Application, 18th Oct., 1895
Complete Specification Left, 14th July, 1896-Accepted, 17th Oct., 1898
•
PROVISIONAL SPECIFICATION.
Improvements in Apparatus for Rotating Telescopes for Astronomical
and other Purposes.
I, JOHN OVERSTALL, of 24, Alexandra Road, Finsbury Park, London in the
County of Loudon, Optician, do hereby declare the nature of this invention to be
As follows:-
Equatorially mounted telescopes for astronomical purposes are usually provided
with clockwork mechanism devised to rotate the telescope at a given speed,
adjusted to neutralise the displacement of the line of sight due to the rotation of
the earth, and thus maintain the field of vision of the telescope fixed upon a given
object.
The desired movement has hitherto been imparted to the telescope directly
through the driving clock. This method necessitates a powerful driving, mechanism
with heavy trains of wheels and consequent waste of energy and increase of cost
and these inconveniences increase in proportion to the increased size and weight of
the telescope. My invention is designed to obviate these drawbacks, and consists
in providing means for rotating the telescope by the application of direct motive
power thereto independently of the clock movement which then serves merely to
check and control the motion.
In carrying my invention into effect attach to the polar axis of the equatorial
stand a circle bearing teeth on its periphery into which a tangent screw or other
equivalent devico is arranged to gear. The taugent sorow shaft bears a drum
upon which is wound a cord provided with a suitable weight; the drum is capable
of being wound up without turning the tangent screw, The axis of the tangent
screw is prolonged and bears a toothed wheel arranged to actuate an ordinary
balance wheel or other light clock suitable for controlling the motion. No clock
main-spring is then necessary as the weight on the tangent screw drives both the
telescope and clock.
DL! AL 110ne
Improvements in Apparatus for Rotating Telescopes for Astronomical
and other Purposes.
I JOHN OVERSTALL, of 24, Alexandra Road, Finsbury Park, London, in the
County of London, Optician, 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 :—
Equatorially mounted telescopes for astronomical purposes are usually provided
with clockwork mechanism devised to rotate the telescope at a given speed,
adjusted to neutralise the displacement of the line of sight due to the rotation of
the earth, and thus maintain the field of vision of the telescope fixed upon a given

page_text: The desired movement has bitherto been imparted to the telescope directly through
the driving clock. This method necessitates a powerful driving mochanism with
heavy trains of wheels and consequent waste of energy and increase of cost, and
these inconveniences increase in proportion to the increased size and weight of the
telescope.
My invention is designed to obviate those drawbacks, and consists in providing
means for rotating the teloscope by the application of direct motive power thereto
independently of the clock movement, which then serves merely to check and
control the niution.
In order more clearly to set forth my invention and the mole of carrying the
same into effect, I will now proceed to describe the same with reference to the
accompanying drawines, in which
N. circle fixed to M.
O. bracket for tangent screw I and fixed to declination bearing Q.
P. circle carrying clock tangent circle B fixed to and revolving with circle H.
Q. declination bearing.
Figure 1 represents an elevation of the apparatus with the telescope attached.
Figure 2, represents a section of the equatorial stand.
Figure 3 represents a side elevation of the tangent screw and universal joint for
hand movement.
Like parts are indicated by the samo letters throughout the drawinga.
The circle or sleeve B is secured to the upper tangent cirole H by means of a
clamp J in such a manner that A can be connected or disconnected with the clock
movement at will. The circle H is also not fixed directly to the polar axis A but
is connected therewith by means of the upper tangent screw, the end of which is
shewn at I. The drum D on the shaft of the tangent screw C bears the weight E
which drives both the telescope and the clock G. This clock may be of any usual
pattern for the purpose of controlling and regulating the movement and may have
a balance wheel pendulum or governors as preferred, but in place of a mainspring,
the weight E supplies the motive power. The drum D is arranged by means of a
pawl and ratchet to admit of the weight being wound up without turning the
spindle. The wheel F imparting motion to the clock has sich a number of teeth
as to allow the tangent screw, when the clock is properly adjusted, to turn at suoh
a speed as to cause the circle B to make one revolution in 24 hours.
In another modification of the driving arrangement I replace the tangent
Borew C by a pinion, gearing in like manner with B and bearing at the other end
of its shaft the wheel as aforesaid: in this case the shaft of the pinion could be
arranged parallel or at any angle to the polar axis in place of transversely as
shown in the drawing.
The circle B has no direct connection with the polar axis, but is attached to the
circle H by the clamp J as aforesaid.
When the clamp J is tightened up, the circles H and P are connected to the
circle B. The circle H is connected with the declination bearing Q by means of
the tangent screw I supported by the bracket O which is fixed to the declination
bearing: consequently the clock rotates the declination bearing. The hand
control of the motion is effected in the following manner.

page_text: By means of the handle K, connected to the tangent sorew I by a universal:
joint L, the said screw can be rotated in either direction at will. According as the
tangent screw I is rotated in the one direction or the other, the speed of revolution.
of the polar axis A will be accelerated or retarded.
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 :-
1. In apparatus for rotating equatorially mounted telescopes, the application of
the motive power directly to the shaft of the actuating tangent screw or pinion
substantially as described."
2. The apparatus for rotating and controlling equatorially mounted telescopes.
substantially as described and shown in the accompanying drawing.
Dated this 14th day of July 1896.
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C., Patent Agents for the Applicant..