IMPROVEMENTS IN SPECTROSCOPES CHIEFLY FOR USE WITH ASTRO- NOMICAL TELESCOPES
Year: 1876

page_text: LETTERS PATENT to Frank McClean, of Ferncliffe, Tunbridge Wells, Civil
Engineer. "IMPROVEMENTS IN SPECTROSCOPES CHIEFLY FOR USE WITH ASTRO-
NOMICAL TELESCOPES,”
Sealed the 23rd March 1877, and dated the 28th September 1876.
PROVISIONAL SPECIFICATION left by the said Frank McClean at the Office
"IMPROVE-
of the Commissioners of Patents on the 28th September 1876.
FRANK McCLEAN, of Ferncliffe, Tunbridge Wells, Civil Engineer.
MENTS IN SPECTROSCOPES CHIEFLY FOR USE WITH ASTRONOMICAL TELESCOPES."
This Invention of improvements in spectroscopes chiefly for use with astronomical.
telescopes, consists in the combination of a concave cylindrical lens with a prism or
prisms to be applied to astronomical or other telescopes.
It is to be used as the eye piece of a telescope and is in adjustment when the
concave lens is at the distance of its own focal length inside the focus of the
telescope.
The novelty of the Invention consists in the particular application of the concave.
cylindrical lens. It intercepts the pencil of rays converging from the speculum or
object glass when its section is about the size of the pupil of the eye. In the
direction of the axis of the lens and of the prism or prisms, the rays of light are not
interfered with and produce the width of the stellar spectrum on the retina of the
observer. In the direction across the axis of the lens and of the prism or prisms
the rays are rendered parallel and in that state pass through the prism into the eye
and form upon the retina the spectrum of the star.
In order to compare the spectrum of the star with other spectra, the image of an
illuminated slit or of the required point of light is thrown into the field of view
along with the image of the star, and the two analized by the spectroscope simul-
taneously. Apparatus suitable for this latter purpose is already in use and no new
Invention is claimed in this respect.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by the
said Frank McClean in the Great Seal Patent Office on the 28th March 1877.
"IMPROVE-
FRANK MCCLEAN, of Ferncliffe, Tunbridge Wells, Civil Engineer.
MENTS IN SPECTROSCOPES CHIEFLY FOR USE WITH ASTRONOMICAL TELESCOPES."
This Invention of improvements in spectroscopes chiefly for use with astronomical
telescopes, consists in the combination of a concave cylindrical lens with a prism or
prisms to be applied to astronomical or other telescopes.
It is to be used as the eye piece of a telescope and is in adjustment when the
concave lens is at the distance of its own focal length inside the focus of the
telescope.
The novelty of the Invention consists in the particular application of the concave
cylindrical lens. It intercepts the pencil of rays converging from the speculum or
object glass when its section is about the size of the pupil of the eye. In the
direction of the axis of the lens and of the prism or prisms the rays of light are not
interfered with and produce the width of the stellar spectrum on the retina of the
observer. In the direction across the axis of the lens and of the prism or prisms
the rays are rendered parallel and in that state are analysed by the prism and pass
into the eye and form upon the retina the spectrum of the star.
In order to compare the spectrum of the star with-other-spectra the image of an
illuminated point of light is thrown into the field of view along with the image of
the star and the two analysed by the spectroscope simultaneously. Apparatus
suitable for this latter purpose is already in use and no new Invention is claimed in
this respect.
In the Drawing forming part of this Specification Figure 1 is a section of the
tube or eye piece of the telescope showing the position of the concave cylindrical
lens and the direct vision prism a.
"
The Invention consists in the application of the concave cylindrical lens b to a
direct vision prism, and the concave cylindrical lens it will be seen is located
between the prism as shown and the object glass or speculum of the telescope
neither of which it is necessary to show.
The proper curves of the lens are not shown, neither is the arrangement of the
angles of the prism intended to be correct; the proportions of either are not the
subject of the Patent but are entirely within the province of the optician and
dependent on the instrument to which the apparatus is to be adapted.
Having now described and particularly set forth the nature of the Invention and
the manner of carrying the same into effect, I would have it understood that what
I claim in the herein in part recited Letters Patent is, the combination of a concave
cylindrical lens with a prism or prisins to be used as a spectroscope in astronomical
or other telescopes substantially as described.
In witness whereof, I, the said Frank McClean, have hereunto set my hand
and seal, this Twenty-eighth day of March, in the year of our Lord One
thousand eight hundred and seventy-seven.