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Патент USA US2136995

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Nov. 15, 1938;
Filed Aug. 17, 1936
' Patented Nov.-15, 1938'
Application August 17, 1936, Serial vNo. 96,506
In Germany July 6, 1935
3 Claims.
(Cl. 88-217)
This intention consists of’ an improved sextant
in Whi‘ihfjithe setting. can be particularly easily
passes, after re?ection by the two mirrors I0 and '
9 and by the plane parallel prism members‘ 8 and
and reliably effected even from an unsteady posi-
5 into the telescope, the image of the object ob
tion such as on'aircr‘aft or ships.
served being shown sharply in the geometrical
The sextant in alli'its forms has an arti?cial
horizon device which consists, of a re?ecting sur‘face which adjusts itself independently of the
manner in which the instrument is held.
plane bounded by the shutter l1. Another part ‘5 _
of the parallel light re?ected by the mirrors I0
and 9 strikes the-swinging mirror l2 and after
The ' re?ection in the surfaces 1 and 6 also passes to
mirror surface may be a level surface located
10 externally‘ of the instrument, for example, may
1 be a liquid mirror. It may, also, be connected
with the instrument either as a liquid mirror or
' a mirror (swinging mirror) rigid in itself and
?oating and/or rotatable in bearings (suspended
the telescope. The image of the object observed,
re?ected by the swinging mirror I2, is also shown 10
sharply in the geometrical plane provided by the _
shutter l1. As the one image is re?ected by an
even numberand the other by an uneven number
of mirror surfaces,~ the one image is' seen upside
- 15 mirror) which may also be inclined in relation
to the horizon.
down and the other in erect position.
In Fig. 2 is shown how the ?eld of vision bound
Various embodiments of the invention are
illustrated by way of example in the accompanying drawing.
-m' In the drawing:
Fig. 1 is a diagrammatic view in side elevation
ed by the shutter l1 appears.
The points a, b, 0 Shown in full lines, indicate
‘ and partly in section illustrating one arrange-
ment of the optical elements of the sextant.
Figs. 2, 3. 4 and _5 illustrate the ?eld of vision
25 bounded by the shutter of Fig. 1.
Figs; 6 and 7 diagrammatically illustrate an-
other form of the sextant wherein Fig. 7 is a
dotted line is the line of symmetry of the two
superposed images. On this line appear the image
and the re?ected images of all those points of
the ?rmament for the altitude of which the 25
sextant is set.
In order to obtain better observation of“ the
side elevational view partly in section and Fig. 6
relation of the image and the ‘re?ected image
one of the two images may be oifset slightly in
Fig. 8 is a diagrammatic elevational view of a
scale arrangement 'for the sextant.
In the embodiment illustratedin Fig. 1, I denotes a telescope with the objective 2; the eye
' 35 piece 3 and the eye lens 4. In front of the objec
tlve 2 is located a pentagonal prism 5 with the
re?ecting surfaces 6 and 1. The prism 5 for the
passage of the rays extending therethrough is
extended by means of a prism wedge 8 to a body
40” with parallel planes. '
The reflecting surface 6 is transparently mirrored while the surface 1 is entirely mirrored.
9 is a ?xed mirror; 'I'0 a mirror rotatable about
the axis as in the known arrangement of ordinary
45 mirror sextants.
The angle between the ?xed
mirror 9 and the rotatable mirror l0 alone determines the altitude of the star observed.
I2 is a mirror arranged beneath the pentagonal
prism 5. The mirror I2 is secured to the swinging
three star images visible in the ?eld of vision.
The three small circles a’, b’, 0' denote the re- 20
?ectedl images of the same three stars. The
is a cross-sectional view of the elements shown
‘ ‘30 in Fig. '7.
relation to the other.
The image then appearing 30
in the ?eld of vision is shown in Fig. 3. Three
star images d, e, ,f are visible. (1’, e’, f’ denote
the laterally displaced re?ected star images. The"—~
sextant is set for the star f.
With the sun‘an‘d moon, as soon as the'image
and the re?ected image come into register, &‘
bearing of the centre of the sun or the moon is
provided. If only the upper or lower edge is 3?‘
visible then the upper or lower edge itself can
' at once be observed as shown in Fig. 4.
Moreover, provision may be made for sub-divi
. sion of the one and preferably the image 11017
re?ected into tWo images one above the other.
This result can be attained by means of a double
prism or by means of a Wollaston prism l8, which 45
is interposed if desired in front of the pentagonal
prism in the path of the rays (shown in dotted
lines in Fig. 1) .
. This procedure is convenient when the position
member l3. I4 is the axis of the swinging system I2, l3. The member 13 serves in the example
shown both as a damping disc which swings between the poles of a braking magnet l6. Other
of the observer is- particularly unsteady and the 50
star image observed is continuously oscillating or
vibrating. In taking a bearing of the star the
unsteady re?ected moving image is permitted to
damping devices may, however, also be used.
‘The parallel light from the object observed
swing between the steady double image. In Fig.
5 the zig-zaglines g’, h’, 1" denote the vibrating 55
image, 99, Mt, ii the double images of the cor
responding three stars.
The angle of de?ection of the pentagonal prism
I is in the example shown 90°, the angle of in
between the actual and expected angle can be
read off on the scale 31.
The further necessary and usual devices such
as dark shades, a protecting casing for the swing
clination of the swinging mirror 45°. when this ‘ ing devices, vibration devices for reducing the
angle of inclination di?ers from 45° it makes no friction of the stationary pivoting axis, tilt indi
difference. The instrument should then be used cator (cross inclination levels) and verniers, are
in a position differing from the horizontal by the not shown.
Compared with pendulum sextants of known 10
same amount in order that the line of symmetry
10 of the image and of the re?ected image comes kind with swinging scale, the new pivoted mirror
sextant possesses a number of further advan
in the centre of the ?eld of vision.
In order to give the new sextant a stumpy form
Greater accuracy of readings is obtained, since
in particular in order to be able to keep the
mirrors 3 and II small, it is preferable to arrange ?ner sub-division and also additional scale devices
1‘ the paths of light for the image and the image can be used. Further, after the observation the
to be re?ected not in a position one above the result of the measurement is retained and can be
examined again. High angle ‘observation is not
other as shown in Fig. 1_ but side by side.
In Figs. 6 and 7 is shown how this result can necessary, in fact sighting is always effected in an
the attained.
‘ approximately horizontal direction.
In front of the objective 22 of a telescope 2!
is located the mirror 23 pivoting about the axis
23. Beneath the latter is arranged the pentago
nal prism 24 with the re?ecting surfaces 25, 25'.
In front of the prism 24 is disposed a Fresnel
prism 25 with the re?ecting surfaces 21 and 28.
This prism 25 is arranged at an inclination in
such manner that the path of the light is dis
placed parallel so far upwards and laterally that
it lies at the same height as the path of light
for the non-re?ected image. The arrangement
. is shown in Fig. 6 in cross section.
As the heavy segment on a pendulum is dis 20
pensed with very much shortened periods of vibra
tion can be obtained.
It is particularly suitable to form the damping
disc serving as a pendulum weight as a pendulum
having the minimum period of vibration.
The arrangement for observing the natural
horizon permits control of the arti?cial swing
ing mirror horizon and inversely there can be de
termined whether an unreliable natural horizon 30
can be used for a measurement. Finally the dip
of the horizon can be measured by re?ection of
The order of arrangement of the three optical
aids, swinging mirror, pentagonal prism and
the horizon on itself.
Fresnel prism may be as desired.
and the manner in which the same is to be per
In the embodiment shown in Figs. 6 and 7
the‘position of the swinging mirror and of the
formed, I claim:
prism are interchanged in relation to the ar
rangement shown in Fig. l. The pivoted mirror
in this case consists oi.’ a transparent mirrored
plane parallel plate. Thesurfaces 25. 25' of the
pentagonal prism are entirely mirrored.
29 is
-_ the ?xed mirror and 30 the mirror rotatable
about the axis 3i in a known manner.
It is particularly simple to arrange the new
45 sextant so that it can be used for taking observa
tions with a natural horizon.
In the embodi
Having described the nature of the invention
1. In a sextant, an index mirror for re?ecting
light proceeding from an object to be observed,
an eye-piece arranged at one end of the sextant,
a ?xed mirror positioned at the other end of the
sextant for re?ecting the light of the index mirror
in a direct path into the eye-piece so that a ?rst
image of the object may be viewed at the ?rst end
of the sextant, angularly disposed transparent re
?ecting means interposed in the direct path of
the light re?ected by the ?xed mirror allowing the 45
light forming the ?rst image to pass there
ment shown in Fig. 6 the two'mirrors 29 and 30 , through, re?ecting means arranged intermediate
are extended for this purpose to the one side. the ?xed mirror and the eye-piece and positioned
laterally of the direct path between the ?xed
Parallel to and adjacent the telescope 2! is lo
cated a second telescope 32. On observation mirror and the eye-piece including at least two to
through this telescope 32 the stars are observed angularly arranged complete re?ecting means one
for intercepting light forming a. second image of
by way of the ?xed mirror 29 and of the rotata
ble mirror 33 and adjacent the ?xed mirror 29 the the observed object proceeding from the ?xed
natural horizon is observed. The arrangement mirror and the second complete re?ecting means
re?ecting the light forming the second image 55
55 consisting of the swinging mirror and the prism
transversely with respect to the direct path of the
thus do not lie in the path of the rays.
In Fig. 8 is shown diagrammatically a special ?rst image onto the transparent re?ecting means,
scale arrangement which cannot be ?tted to said transparent re?ecting means being arranged
known sextants having a swinging arc.
, to re?ect said transverse light image into said
The index arm 34 with the index 35 is ?rmly
connected with the rotatable mirror 33. With
the rotatable system 33, 34, 35 is connected 9.
scale carrier 33 which has a scale 31 and a pointer
33. The pointer 33, on rotation of the system
33 to 33, passes along the arc 39 on the scale
carrier 43. If now the index 35 is adjusted to
the zero point of the scale 31 located in the
middle and the system 33 to 38 is turned as a
" unit about the common axis, then by means of
70 the pointer 33 the set altitude can be read off
on the scale 33. If a de?nite expected,‘ value
is set on the scale 33 and ?xed in this position
and then on the observation only» the arm 34
with the mirror 33 and the index 35 is moved
75 then by means of the pointer 35 the difference
eye-piece, and one of the re?ecting means inter
mediate of the ?xed mirror and the eye-piece be
ing swingably mounted to be moved by gravity.
2. In a sextant, an index mirror for re?ecting
light proceeding froman object to be observed, an
eye-piece arranged at one end of the sextant, a 65
?xed mirror positioned at the other end of the
sextant for re?ecting the light of the index mirror
in a direct path into the eye-piece so that a ?rst
image of the object may be viewed at the‘ ?rst end
of the sextant, a pentagonal prism interposed in 70
the direct path of light re?ected by the ?xed
mirror, one face of said prism having a transpar- I
ent mirrored surface permitting the light forming '
the ?rst image to pass therethrough, another face;
of the prism having a completely mirrored sur-l‘
'face so as to re?ect a transverse beam of light
onto the transparent mirrored surface 01’ the
prism, said transparent mirrored surface being
positioned to re?ect the re?ected transverse beam
of light into the eye-piece, and a pendulum actu
‘ ated mirror positioned laterally of the direct path
of light forming the ?rst image and arranged in
termediate of the ?xed mirror and the eye~piece
for re?ecting light forming a second image pro
10 ceeding from the ?xed mirror onto the completely
mirrored surface of the prism whereby the second
image is inverted in being re?ected into the eye
3. In a sextant, an index mirror for re?ecting
15 light proceeding from an object to be observed, an ‘
eye-piece arranged at one
?xed mirror positioned at end of the sextant, a
the other end of the
sextant for re?ecting the light of the index
mirror in a direct path into the eye-piece so that
a ?rst image of the object may be viewed at the
?rst end of the sextant, a transparent‘ swingable
mirror interposed in the direct path of light form
ing the ?rst image and adapted to be moved by
gravity to re?ect transverse beams of light into
the eye-piece, a pentagonal prism arranged later 5
ally of the direct path of light forming the ?rst
image, said prism having two mirrored surfaces
and one mirrored surface being arranged to re
?eet light onto said transparent mirror, and prism
re?ecting means positioned intermediate the ?xed 10
mirror and the pentagonal prism for intercepting
light from‘ the ?xed mirror and re?ecting the
same onto the other mirrored surface of said
pentagonal prism to provide a second image of
the observed object which appears inverted in the I
eye-piece in being re?ected thereinto.
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