Improvements in Sextants, Octants, and like Instruments.
Year: 1896

page_text: Dale of Application, 25th Nov., 1896-Accepted, 23rd Jan., 1897
[Communicated from abroad by the Firm of C. PLATH, of No. 25 Stubenhuk,
Hamburg, in the Empire of Germany, Manufacturer of Nautical Instruments.]
Improvements in Sextants, Octants, and like Instruments.
I, HENRY HARRIS LAKE, of the Firm of Haseltine, Lake & Co., Patent
Agents, 45 Southampton Buildings, in the County of Middlesex, 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:-
My invention relates to improvements in reflecting instruments for measuring
angles (sextant, octant or the like) and the object of my improvements is to
appropriate such reflecting instruments or make the same more convenient for
night work i.e. for observations at night.
I attain this object by the means illustrated in the accompanying drawing, in
which I have shown as an example a reflecting octant made in accordance with my
invention.
In the reflecting instruments hitherto in use the half-silvered horizon-glass fixed
to the frame has in general a height of about 30 mm. and a breadth of about 25 mm.
This relatively small area, however, makes or renders the operation of searching
and finding out of the celestial objects and the horizon in observations at night
somewhat difficult, whereby an unnecessary waste of time is caused.
This inconvenience may be obviated or remedied by enlarging or increasing the
area of the said horizon-glass in the manner shown in the drawing. In carrying
out my invention I prefer to give the horizon-glass a a height of about 65 mm.
and a breadth of about 35 mm., and to employ a telescope 6 enlarged accordingly.
In the present case the telescope may have an object-glass of a diameter of about
The arrangement being thus that the silvered lower part of the horizon-
glass properly extends to the axis or centre-line of the said enlarged telescope, and
the non-silvered upper part is nearly twice as long in height as the silvered part of
the said horizon-glass, in order to have the upper cross part of the frame of the
horizon-glass, by its being higher than the object-glass, removed out of the field of
view of the telescope.
45 mm.
A reflecting instrument provided with my improvements above described
facilitates in a high degree the searching and finding of the objects to be observed
in the darkness as well as the operation of bringing their reflected image to
coincide with the sea horizon or any other object respectively.
My improved reflecting instrument necessitates, if any, only one shade or screen
of coloured glass between the fixed horizon-glass and the movable index-glass,
and this shade will but be used in adjusting the reflecting instrument at day-time
n order to prevent the eye of the observer from being injured by the glare of the
un light.
My improved reflecting instrument is exceedingly simple in construction, efficient
n use and comparatively very low-priced; it is not designed to form generally a
ubstitute for the ordinary reflecting instruments for taking observations in the
lay-time but is to be used instead of the said day-instruments when observations
re to be taken at night.