Improvements in Sextants and Octants, and the Fitting of these and similar Instruments in their Cases.
Year: 1893

page_text: Date of Application, 23rd Aug., 1893
Complete Specification Left, 23rd May, 1894-Accepted, 23rd Aug., 1894
PROVISIONAL SPECIFICATION.
Improvements in Sextants and Octants, and the Fitting of these and
similar Instruments in their Cases.
GEORGE WILSON HEATH of Crayford in the County of Kent, Managing
Scientific Instrument Makers,
Director of Heath and Company Limited
Observatory Works Crayford in the County of Kent and on their behalf do
hereby declare the nature of this invention to be as follows :-
-
The object of one part of this invention is to improve the horizon glass
adjustment as mentioned in the Patent Number 1984 of May 19th 1879 known as
the duplex adjustment, by making the horizontal adjustment to be independent of
the vertical by fixing a further casing with its springs or other means of movement
within the larger and vertical adjustment casing and by fixing this further case
and its appendages to the base plate on which the horizontal adjustment pivots are
fixed and not upon the limb of the instrument direct as heretofore by this means
I obtain direct vertical or horizontal adjustment and avoid the oblique motion
heretofore resulting from either the fixed, swing or duplex mode of adjusting
instruments.
Another improvement relates to the horizon clip and glass which 1 use in
conjunction with the first mentioned mode of adjustment. I preferably use a very
wide horizon glass the whole of which is silvered and I allow no plain or unsilvered
part at all and I hermetically seal and fix this silvered glass in the frame which
has no upper portion so that the view from a telescope with a large object glass is
unimpeded by any upper part to the horizon glass or its brass framing, in connec-
tion with these wide horizon glasses I use very long necked frames for the
necessary dark glasses.
Another improvement is a slip spring fitting instead of the ordinary screw by
which the telescope is fitted to the sextant and to this or other telescope I fix a
screw eye head with a revolving inner frame containing several tints of dark
glasses, thus with one eye head I obtain several tints or shades of colour enclosed
in oue frame head. I further improve the fixing of the sextant magnifier by making
it so to swing that the right angle according to the differing lights may be obtained
thus greatly facilitating the reading off of the arc and vernier.
It is usual to fix all sextants in cases by wooden fittings round the handles with
or without holding buttons and with these are generally added top packings to
press the instrument into its case, my improvement consists of the use of a spring
rod passing through or around the handle which clamps the instrument on its
being placed in the box and I can do away with every other fixing. I also cause
the lid to lock when pushed down by means of a spring and catch, thus fixing the
whole instrument without upper packings, handle buttons or even hooks as a
necessity.
Dated this 21st day of August 1893.

page_text: COMPLETE SPECIFICATION.
Improvements in Sextants and Octants, and the Fitting of these and
similar Instruments in their Cases.
I, GEORGE WILSON HEATH, of Observatory Works, Crayford, in the County
of Kent, Scientific Instrument Maker 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, reference being had
to the accompanying three sheets of drawings and to the letters and figures marked
thereon, that is to say:-
The object of one part of this invention is to improve the horizon-glass
adjustment described in the Specification of a Patent granted to me bearing date
the 19th day of May 1879 No. 1984, and known as the "duplex" adjustment by
making the horizontal adjustment to be independent of the vertical, and this I
effect by mounting the devices, by which the horizontal adjustment is made, in a
special casing or other suitable parts fixed to the base plate in which the horizontal
adjustment pivots turn, instead of mounting such devices in the casing, or other
part fixed direct to the limb or frame of the instrument as heretofore, the said
special casing or other parts being contained within the larger and and vertical
adjustment casing. By this means I obtain direct and independent vertical and
horizontal adjustments, and avoid the oblique motion heretofore resulting from
either the "fixed," "swing 66
ог duplex" mode of adjusting the horizon-glasses of
these instruments.
"
In the drawings hereto annexed
Figure 1 is a sectional elevation showing the back of a horizon-glass frame with
its adjustments constructed and arranged in accordance with this part of my
invention,
Figures 2 and 3 are sectional elevations taken on lines 1-1 and 2-2 respectively
of Figure 1, and
Figure 4 is a front elevation of the horizon-glass with its frame.
A represents part of the frame of the sextant or octant, B the casing secured
to the underside of the frame and containing the vertical and horizontal adjusting
devices. C is the base plate in which the horizon-glass frame D pivots in the
usual way.
The base plate C has a pivot C' which turns in the socket A¹ of the
frame A as usual for the purpose of the vertical adjustment of the horizon-glass.
Cis the tail piece secured to or formed with the base plate C and on which the
adjusting screw C³ and spring C₁ (see Figure 2) act, in the well known manner, to
effect the vertical adjustment of the horizon-glass by swinging it on its pivot C.
E is the special casing above referred to fixed to or formed with the underside of
the base plate C and projecting downwards therefrom into the casing B. D' is the
tail piece projecting downwards from the horizon-glass frame D through the base
plate Cinto the special casing E. D' is a spring which presses the tail piece D¹
constantly against the point of the adjusting screw D³ tapped into the end of the
casing E. Bis a hole in the casing B through which a suitable instrument can be
passed for turning the screw D³. The spring D' and screw D' act and react on
the tail piece D' in the same manner as the adjusting screw C³ and spring Cact
and react on the tail piece C³, and in the manner now well understood in connection
with the adjustments of the horizon-glasses of sextants and octants.
It will now be understood that by turning the adjusting screw C³ in one direction
or the other, the base plate C, and the horizon-glass mounted on it, are turned on
the pivot C' to effect the vertical adjustment, and that in this movement the special
casing E, the tail piece D' and the adjusting devices D' and D' are moved also
quite independently of the casing B, so that the adjustment horizontally of the
horizon-glass is not affected or altered in any way by the vertical adjustment. On
the other hand by turning the adjusting screw D³ in one direction or the other the

page_text: horizon-glass is turned on its pivots on the base plate C to effect the horizontal
adjustment without affecting, or altering in any way, the vertical adjustment effected
by the devices C' C*.
It is obvious that the sides of the casing E may be dispensed with, the ends only
being absolutely necessary, the one to carry the adjusting screw D³ and the other
to support the spring D.
Another improvement relates to the horizon-glass and its clip. I preferably use
a very wide horizon-glass F the whole of which is silvered and has no plain or
unsilvered part at all, and I sometimes hermetically seal or cement this silvered
glass in its place in the frame so as to prevent the entrance of water behind it,
and otherwise to preserve it from injury. The frame has no upper portion, so that
the view from a telescope with a large object glass is unimpeded by that part of the
frame which in ordinary horizon-glasses carries the plain or unsilvered part of the
glass. When the glass is hermetically sealed or cemented in its frame it needs no
other fixing, but when the glass is not cemented into its frame I prefer to fix it in the
following manner :-The back of the glass F bears against the three projections G
on the back D× of the frame. H is a clip piece having a back, top, and two sides
as shown in Figures 1, 2, 3 and 4. This clip piece is provided with claws H¹ which
take in front of the glass F and hold it in place against the three projections G.
I is a spring secured at both ends to the back of the clip piece H and having a
screw I tapped through its centre. The point of this screw passes through a hole
in the back of the clip piece H and bears against the back Dx of the frame. When
the screw I is screwed up, the claws H' are drawn against the front of the glass F
and press the latter against the projections G with a pressure proportionate to the
tension of the spring I produced by the pressure of the screw I against the said
back D, and the glass is thereby held steadily in place without being bent or
broken.
It will be seen that the frame of the horizon glass has no upper part except the
narrow edge of the top of the clip piece H so that the view from a telescope with
a large object glass is not impeded.
The index glass may also, be secured in a similar way, as shown in Figures 5
and 6, in which Figure 5 is a back view of the index glass frame, and Figure 6 a
section on line 3-3 of Figure 5. J is the bracket secured to the index arm,
K the index glass silvered at the back as usual and bearing at its lower edge
against two projections J¹ on the bracket J. H is a clip piece similar to that
shown in Figures 1 to 4 and similarly furnished with claws H', spring I and
screw For the purpose of adjusting the index glass, so that it stands
perpendicularly to the limb of the instrument, an adjusting screw J2 is tapped into the
bracket J, its end hearing against the back of the index glass K forming the third
projection for the latter to bear against. The screw J' can be turned by a screw-
driver or other suitable instrument introduced through a hole in the back of the
clip piece H. By screwing in the screw J2 the upper edge of the index glass K
is pushed outwards against the tension of the spring I, and by screwing the
screw outwards the said spring I draws the upper edge of the iudex glass K
inwards.
Another improvement relates to the means of fixing the telescope to the
instrument. According to one arrangement shown in Figures 7, 8, 9 and 10,
instead of screwing the telescope L into the supporting ring as usual, I make
the latter in two halves M M', the upper half M being hinged at M² to the
lower balf M', and I form a V-groove M³ in the interior of the said ring
and provide a correspondingly shaped projection L on the telescope L,
which projection fits into the said groove. When it is required to place the
telescope in position in the instrument, the upper half M of the ring is turned
on its hinge, and the telescope is placed in position with the lower half of its
projection L' engaging in the V-groove M³ in the lower half M' of the ring;
the upper halt M of the ring being then closed down into the position shown in the
figures, its groove M³ engages with the upper half of the projection L' and the

page_text: telescope is thereby held firmly and steadily in position. The upper half M of
the ring is held in the closed position by means of a spring catch or other suitable
means; for example, a convenient and effective means is shown in Figures 8 and 9
consisting of a disc or cam M* turning on a pin M' secured in the lower half M¹ of
the ring. A groove M is formed in the disc M' and a projecting part M' on the
upper half M of the ring passes, when shut down, through a notch in the edge of
the disc into the said groove Me, and the inner surface of the groove M being
shaped eccentrically, when the disc is turned the said eccentric surface bears on
the part M² and presses the upper half of the ring forcibly downwards. The
spring M bears against the inner surface of the disc M* and exerts friction to
prevent the latter from turning too easily. When it is required to open the ring,
to insert or remove the telescope, the disc M is turned so that the notch in its
edge coincides with the projection M', and the upper part M can then be turned
on its hinge. In order to save trouble in adjusting the disc M* so that the notch in
its edge comes exactly opposite the projection M', a recess is formed in the opposite
side of the disc, into which the end of the spring M³ takes as soon as the notch is
brought opposite the said projection M'. The aforesaid recess, and the part of the
spring that takes into it are so shaped that they do not offer material opposition to
the rotation of the disc, although the entrance of the spring into the recess is
sufficient to indicate the fact that the notch in the disc has been brought opposite
the projection M'.
The upper half M of the ring may be pressed open automatically as soon as
released from the disc M', or from the spring or other fastening, by means of a
spring such as that shown at M' for example.
When the telescope is mounted in the manner shown in Figures 7 and 8 the
adjustment of the axis of collimation parallel to the plane of the limb of the
instrument cannot be effected by the ordinary adjustment on the collar of the ring
of the rising piece; I therefore apply the adjustment to the socket N which
receives the stem or rising piece M of the ring M M. For this purpose the said
socket N is formed with a flange N' secured and adjusted to the frame A of the
instrument by the capstan or other suitably headed screws N' passing through holes
in the frame A and tapped into the said flange N¹. These screws are placed as
near as may be in the diametral line of the flange N¹ which stands in the plane of
the axis of collimation of the telescope. N³ are fulcrum points secured in a
diameter of the flange N at right angles to that in which the screws N' are placed.
These fulcrum points are drawn against the underside of the frame A by means of
the screws N2, and by turning one screw in one direction and the other in the
opposite direction, the socket N, and with it the telescope L, can be rocked or
turned on the fulcrum points N' until the axis of collimation is brought exactly
parallel to the plane of the limb.
If preferred, a spring may be substituted for one of the screws N' as will be
readily understood by persons conversant with the manufacture of this kind of
instrument.
Figures 11 and 12 show another method of mounting the telescope in its ring
without screwing it thereinto. M is the ring, the stem or rising piece N of which
takes into and is secured in a socket connected with the frame of the instrument in
the ordinary way. O is a tube secured at one end to the ring M by adjusting
screws and fulcrum points in the same way as in what is known as the collar of the
ring of the rising piece. P is a tube sliding steadily in the tube and carrying at
its outer end the object glass P₁ of the telescope. This tube P is moved in and
out in the tube by means of a rack P' secured to the said tube P and gearing
with a pinion P³ operated by the milled button P+, the axis of which turns in a
bearing on the tube O. By these means the focussing of the telescope is effected
by moving the object glass instead of the eye glass, as beretofore, and the focussing
is therefore effected much more conveniently than by drawing out or pushing in
the eye glass draw tube Q more or less as at present practised. In this case the
various draw tubes, namely, the inverting draw, the direct draw, and the star or

page_text: blank draw, are adapted to be pushed into the small end 0¹ of the tube O up to a
stop, and to remain in that position while the observation is being made. The
small end of the tube O is or may be split so as to form a spring tube into
which the draw Q is slipped and by which it is grasped and held steadily in the
required position. The focussing is effected, as before explained, by moving the
object glass P¹. In some cases the rack and pinion may be dispensed with and
the tube P with the object glass P' be slid inwards or outwards in the tube O by
hand. On the other hand if preferred the object glass may remain stationary and
the draw tube be slid inwards or outwards in the tube O' by hand or by a rack and
pinion arrangement similar to that shown in the drawings in connection with the
tube P, the essential feature of this part of the invention being the division of the
telescope into two parts one fixed permanently to the rising piece forming what
I call a slip spring fitting and the other part added thereto as and when required.
I prefer to connect the object glass or the eye glass to the telescope by mounting
it in a short piece of tube which slips into or over the carrier tube of the telescope
instead of being screwed into or over the same.
Another improvement relates to a screw eye-head to be fixed to the eye end of
the telescope of a sextant or octant, with a revolving under frame containing
several tints of dark glasses so that with one eye-head I obtain several tints or
shades of colour enclosed in one frame head. This improvement is illustrated in
Figures 14, 15 and 16 in which Figure 14 represents the front or eye end of a
telescope with the aforesaid screw eye-head attached thereto; Figure 15 is a side
view of same, and Figure 16 is a view similar to Figure 14 but with the front cap
removed. R is a casing screwed on to the eye end of the telescope, R¹ is the
aforesaid under-frame, having four openings R behind each of which is fixed a
dark glass differing in tint from either of the others. The frame R' can be rotated
on the pin or stud R' by means of its milled edge which projects through the side
of the casing R as shown. The openings R' in the frame Rare so placed that, as
the frame R is turned round on its stud, any one of them can be brought to coincide
with the eye hole R in the axis of the telescope. A peg R with a rounded end
mounted on the end of a spring R' takes into the holes R' on the edge of the
frame R and serves to hold the latter in position with one of the tinted glasses in
the axis of the telescope while the observation is being made.
Another improvement relates to arranging the sextant magnifier so that it can be
swung into the proper angle according to the differing light to facilitate the reading
off of the arc and vernier..
This part of my invention is shown in Figure 17 which is a plan of a sextant in
its case with the lid open. It will be seen that the magnifier S, instead of being
fixed vertically over the arc and vernier, is hung on trunnions S' turning in
bearings in the part S2 pivotted to the index arm S so that the said magnifier can
be turned into the angle best suited for reading off the observed angle.
It is usual to fix sextants and octants in their cases by means of wooden fittings
around the bandle, with or without holding buttons, and with these are generally
combined top packings in the lid of the case to hold the instrument down.
According to another of my improvements I substitute for these arrangements a
spring rod or catch passing into, through, or around, the handle of the instrument
whereby the latter is clamped and held fast automatically when placed in the box
without upper packings or any other fixing. One method of carrying this part of
my invention into effect is shown in Figures 17 and 18, in which Figure 18 is an
oblique elevation of the parts as seen on section line Z Z of Figure 17 the latter
figure representing a plan of a sextant in its case drawn to a smaller scale than
Figure 18.
T is a bracket secured to the inside of the case U, T' is a rod adapted to slide
in holes in the parts T of the bracket T and provided with a button or finger
piece T at its upper end, and with a spring T which tends constantly to press
the said rod T₁ upwards. T' is a bell-crauk lever turning on a fulcrum T in
the part T of the bracket T. The lower end of the rod T is pin-jointed

page_text: to one arm of this bell-crank lever, and one end of a rod T8 to the other
arm. The other end of the rod T8 is pin-jointed to the lower end of a
catch T turning on a fulcrum T in a carriage T secured to the bottom
of the case U. V is the handle of the instrument and V₁ is a hole made in
the same.
W are blocks fixed to the bottom of the case U and provided with
recesses to receive the ends of the handle V and thereby to steady the instrument
in position, and to guide the handle V, so that when the instrument is placed in the
case the hale V passes over the upper end of the catch T and the hooked part T
of the latter springs into a notch within the hole in the handle by the action of the
spring T, and the instrument is thereby securely held in the case. When it is
desired to take the instrument out of its case it is only necessary to press down the
rod T by the button T3; the hooked part of the catch T is thereby withdrawn
from the notch in the hole V₁ of the handle V, and the instrument can then be
lifted out of the case without any further trouble; and when it is required to refurn
the instrument to its case it is only necessary to place it in position with the ends of
its handle in the recesses in the blocks W, and to press it down when the upper
part of the catch To passes into the hole V' in the handle V, and the hook T
springs into the notch or (if the catch be made long enough and the hole V' quite
through the handle) over the top edge of the said hole, and fixes the instrument.
It is obvious that this holding device may be modified in a variety of ways without
departing from my invention, for example, instead of the catch passing through a
bole in the handle, one or more of the spring catches may be arranged to grasp the
outside of the handle or to take into or over any other suitable part of the instru-
ment, any convenient means being employed to release the catch or catches when it
is desired to take the instrument out of its case.
I also employ a spring catch to lock the lid when it is closed down, and I prefer
to arrange the said spring catch as shown in Figures 19, 20 and 21 of the drawings,
in which Figure 19 is a front view of the lock of the case, provided with the said
spring catch, Figure 20 a similar view with the front plate removed, and Figure 21
a sectional elevation looking from right to left in Figure 19. a is the back plate of
the lock, b.the front plate, c the bolt for locking the case in the ordinary way
governed by the levers d as usual. e is the spring-catch forming part of the bolt c,
the tongues of this spring-catch take into the hasp fon the lid of the case (see
Figure 17) in the usual way. is a pin fixed in the catch e and projecting through
a slot in the front plate 6 of the lock, is a disc hollowed out in front at ', as
shown in Figures 19 and 21, and provided with a cross bar ². This hollowed disc
turns on a pivot i in the front plate and has a notch k taking over the end of the
pin g.
When the disc is turned in the direction of the arrow in Figure 19 the
notch k moves the pin g and consequently the catch e out of engagement with
the hasp and the lid of the case can then be opened. The spring returns the
catch e to the left when the disc is released until a pin m in the catch-bolt comes
against the stop n in the lever d. When the lid is closed the hasp fbears against
the inclined surfaces e¹ of the catch e pressing the latter to the right against the
action of the spring until the points of the catch e are forced by the spring into
the openings in the hasp and the lid is thereby locked.
In place of the usual hooks, I sometimes employ the fastening device shown in
Figures 22, 23 and 24 in which Figure 22 is a view of part of the front of an
instrument case, Figure 23 a view of part of the front of the lid of the same case,
and Figure 24 a section on line 4-4 of Figure 22.
P
q
is a
is a plate let into the front of the case and secured therein by screws.
disc preferably hollowed out in front, as shown in Figure 24, and adapted to turn
on a central screw with its back face in contact with the plate p. 2 are
recesses formed in the back of the disc 4. The recess q' opens out into a notch at
the edge of the disc q as shown at 3 to allow of the entrance into the said recess o
a stud s mounted on a plate t screwed to the front of the lid, as shown in Figure 23
The inner surface of the recess g' is formed eccentrically with regard to the
central screw r. The recess g is of segmental form and receives the end of a sto

page_text: น
pin u secured in the plate p. The ends of the recess q² come against the stop pin u
when the disc q is turned in either direction, so as to limit the motion of the latter.
When the disc is turned into the position shown in Figure 22, one end of the
recess is against the pin u and the opening stands exactly opposite the stud s
so as to receive the latter when the lid is closed down. When the studs has entered
the recess the disc g can be turned, in the direction of the arrow in Figure 22, and
the eccentric surface q of such recess then bears upon the upper side of such stud,
thereby pressing the lid firmly against the case. The other end of the recess
then coming against the stud u prevents the disc q from being turned, so far as to
unduly strain the parts. On turning the disc q in the reverse direction the opening q³
is again brought opposite the stud sand the lid can then be opened.
In order to prevent the disc g from coming in direct contact with the central
screw when turned round, which might tend to loosen the said screw, 1 sometimes
interpose between the disc and the central screw a ferrule v provided with prongs
or teeth which grip the wood and prevent the said ferrule from turning while they
do not prevent the said ferrule from being driven further into the wond by the
pressure of the central screw when it is required to take up the wear and tear of the
back of the disc due to rubbing against the face of the plate p.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
First The improved devices for effecting the horizontal and vertical adjustments
of the horizon-glass independently of each other, which consists in mounting the
adjusting screw and spring for the horizontal adjustment in a special case or
other parts formed with or secured to the base plate in which the horizon-glass
pivots, substantially as described with reference to Figures 1, 2, 3 and 4 of the
drawings.
Second-The use of a horizon-glass silvered all over, that is to say, having no
plain or unsilvered part, substantially as described.
Third The improved means of fixing the telescope to a sextant or octant which
consists of a ring fixed adjustably to the frame of the instrument and made in two
parts M M' hinged together and provided with an internal V-groove, the telescope
intended to be carried thereby being provided with a correspondingly shaped V-ring
or projection L' adapted to take into the V-groove in the ring, substantially as
described with reference to Figures 7, 8, 9 and 10 of the drawings.
Fourth The improved means of fixing the telescope to a sextant or octant which
consists of a tube fixed adjustably to the frame of the instrument and having at one
end au object glass tube adjustable longitudinally therein, or fixed therein or
thereon, and one or more eye-tubes or draws adapted to slide into the other end
thereof, substantially as described with reference to Figures 11 and 12 of the
drawings.
Fifth Mounting the magnifier on the index arm so that it can be set at the
angle best suited for reading the divisions on the limb and vernier, substantially as
described with reference to Figure 17 of the drawings.
Sixth The device for fixing and holding a sextant or octant in its case which
consists of an automatically-acting spring catch, arranged, combined and operated
substantially as described with reference to Figures 17 and 18 of the drawings.
Seventh In connection with the case of a sextant or octant the use of a spring
locking catch, constructed and operating substantially as described with reference
to Figures 19, 20 and 21 of the drawings.
Dated this 2nd der of Mer 1904
G. W. HEATH,
Per W. H. Beck,
115, Cannon Street, London, Agent.