Reflector telescope with upright image

A reflector telescope with upright image having a principal mirror constructed as a concave mirror, wherein in the path of the light rays between the principal mirror and a concave reversing mirror a collector mirror and a folding mirror are arranged, so that in addition foldings occur at the principal mirror and the reversing mirror of a reflector telescope of the Gregorian type. The image ray path in the reflector telescope is folded twice between the concave principal mirror and the reversing mirror as well as twice between the reversing mirror and the principal mirror. Thereby an extraordinarily compact configuration of the light ray path is achieved and as a result a reflector telescope with reduced overall dimensions, reduced weight and diminished type-conditioned image aberrations is created.

FIELD OF THE INVENTION 
The invention relates to a reflector telescope with an upright image with a 
concave main collector mirror for use preferably in medium to high-degree 
magnification. 
BACKGROUND OF THE INVENTION 
There are known binoculars and telescopes which consist of objectives and 
inversion systems for image erection. The objectives can be constructed of 
refracting lenses can comprise mirrors and the inversion systems are 
commonly constructed as lenses or prismatic inversion systems. 
Further, a large number of reflector telescopes of different construction 
are known to be used for astronomical purposes. 
The basic different types are: 
the Newtonian telescope with reversed image, 
the Cassegrainian telescope with reversed image, and 
the Gregorian telescope with upright image. 
Binoculars and telescopes with objectives made of lenses for medium or 
high-degree magnification could be constructed considerably shorter after 
the invention of the teleobjective; besides, in the past due to the use of 
prismatic inversion systems the systems have been either somewhat shorter 
and therefore wider, or still relatively long and therefore based on 
direct vision. 
In the case of telescopes with lens inversion systems very tall 
construction necessarily results. 
Since teleobjectives, especially due to the requirements of correcting the 
chromatic aberrations and of reducing the height of the construction, are 
made of a plurality of lenses, this type of construction including the 
prismatic inversion systems or the lens reversion systems has a cumbersome 
total weight meaning that binoculars or telescopes for medium or 
high-degree magnification cannot be comfortably carried around for a long 
time when traveling. 
In the case of reflector telescopes such as the Newton telescope or the 
Cassegrain telescope, lens reversal systems or prismatic reversed systems 
are needed for the reversion of the image. 
In contrast to the already-mentioned telescope types, the Gregorian 
telescope provides directly an upright image. This is possible because a 
real reversed intermediary image produced by the main mirror is reproduced 
by the collector mirror used as a reversal system, as an upright, real 
intermediary image. 
Essential advantages of the Gregory telescope consist therefore of the 
upright image, the achromatic quality of the mirror and the relatively 
reduced weight. As disadvantages can be mentioned the relatively 
considerable over-all length and the short focal distance of the collector 
mirror in dependence upon the typical image ratio of .beta.=-4, which is 
unfavorable for the image quality. This because the sum of the focal 
distances of the main mirror must and the object distance of the reversing 
mirror be approximately equal to the image distance of the reversing 
mirror. This strong secondary magnification of the first intermediary 
image leads to an increase in image distortion of the main mirror and, on 
the other hand, even when the main mirror is parabolically shaped and the 
reversing mirror is elliptically shaped, additional strong extra-axial 
image distortions occur, due to the considerable ellipticity of the 
reversing mirror determined by the image proportion .beta.=-4. This, in 
addition to the relatively large over-all length, is regrettable for the 
Gregorian telescope, since otherwise it allows for a very light telescope 
construction because of the reduced number of components. A modification 
of the mirror focal distance is not possible in the Gregorian telescope, 
because the sum of the focal distance of the main mirror and the object 
distance of the reversing mirror must be approximately equal to the image 
distance of the reversing mirror. 
The disadvantages of the known reflector telescopes are, therefore, that 
they either must have additional lens of prismatic reversing systems for 
image erection for ground observation (terrestrial observation), or have 
relative large over-all construction lengths or type-conditioned image 
aberrations. 
OBJECTS OF THE INVENTION 
The object of the invention is therefore to provide a reflector telescope 
with reduced over-all length, reduced weight and fewer type-conditioned 
image aberrations thereby eliminating the mentioned disadvantages. 
SUMMARY OF THE INVENTION 
According to the invention, this object is achieved with further optical 
means ensuring that the path of light rays coming from the object is 
foldable more than twice, preferably by folding the ray path twice between 
the principal collector mirror and a reversing mirror. Since in a 
Gregorian telescope the ray path is already folded twice by means of the 
principal concave mirror and the reversing mirror, this additional double 
folding of the ray path leads to an extraordinarily compact configuration 
of the light ray path. 
This is accomplished by providing in the light path a collecting mirror and 
a folding mirror arranged between the concave principal mirror and a 
concave reversing mirror. 
Advantageously, the reversing mirror is a concave mirror and the collector 
mirror and the folding mirror are plane mirrors. 
Because of the arrangement of the reversing mirror, the collector mirror 
and the folding mirror in the path of the light rays and with respect to 
the tube of the telescope the image ray path in the reflector telescope 
can be folded a total six times, namely twice between the concave 
principal mirror and the reversing mirror and twice between the reversing 
mirror and the principal mirror, in addition to the folds at the principal 
mirror and the reversing mirror corresponding to the folds in the Gregory 
telescope. 
According to the invention the diameter of the reversing mirror can be 
increased since it does not obstruct the path of the light rays. The focal 
distance can be lengthened with a typical image size in the range of 
.beta.=-2.3 to .beta.=-3.5, preferably between .beta.=-2.5 and 
.beta.=-3.3. 
The enlargement of the reversing mirror is advantageous for increased field 
of view and the typical value of the image size means a reduced 
ellipticity of the reversing mirror and thereby reduced image aberrations 
and also a reduced further amplification of the image aberrations of the 
principal concave mirror. The fact that the reversing mirror can be 
constructed larger with respect to the principal mirror and its focal 
distance can be lengthened is also advantageous due to the reduced 
amplification of aberrations on the reachable angle of image and in the 
sense of reducing the amplification of image aberrations in the principal 
mirror. 
While in the Gregorian telescope the maximum field of vision reaches 
approximately 40%o, in the reflector telescope according to the invention 
it reaches approximately 67%o. 
The image quality that can be reached is clearly improved by providing a 
parabolically shaped principal concave mirror and an elliptical reversing 
mirror. 
The rectilinear conformation of the light ray path in connection with the 
compact construction of the reflector telescope according to the 
invention, its reduced weight and the improvement of its optical 
characteristics widens the field of application. 
Particularly, the rectilinear configuration of the light ray path favors 
use of the system for binocular vision. 
Advantageously the folding mirror and/or the reversing mirror are arranged 
at a small distance from or tangentially to the cylindrical portion of the 
reflector telescope wall. In accordance with the invention, they extend as 
little as possible or not at all into the parallel light ray path defined 
by the main concave mirror. 
An intermediate image produced by the main concave mirror can lie in the 
vicinity of the collecting mirror. 
The intermediary image produced by the main concave mirror can be 
reproduced by the reversing mirror into a second, real, upright 
intermediate image in the vicinity of the principal mirror translucent in 
its central area, which image can be infinitely reproducible from the 
ocular. 
Advantageously the real image of the entrance pupil or aperture, defined by 
the frame of the main concave mirror, can be generated in the vicinity of 
the first real intermediate image, but in the reversed ray path beyond the 
reversing mirror. The real (pupillar) intermediate image can be reproduced 
via the ocular in a real exit pupil. 
Means for the protection against infiltrated light can be provided, such as 
an opaque conical tube in the shape of a frustoconical casing, which can 
be attached centrally with respect to the axis of the telescope tube via 
an optical lens cemented to the principal concave mirror or which can be 
mounted on the principal mirror by any other mechanical means. 
Advantageous embodiments of the principal concave mirror and the reversing 
mirror are for instance the cases when the principal mirror and the 
reversing mirror are constructed as spherical surface mirrors, when the 
principal mirror and the reversing mirror are constructed as Mangin type 
mirrors or when the principal mirror is constructed as a parabolical 
surface mirror and the reversing mirror as an elliptical surface mirror. 
For the purpose of focusing, of sharp adjustment of the reflector telescope 
to the respective object, the reversing mirror can be movable in the 
direction of its optical axis. This way the internal focusing can be 
carried out. 
Also, the reversing mirror, the collecting mirror and the folding mirror 
can be built as rigidly interconnected parts of a structure group, which 
in turn is slidable for the purpose of focusing in the direction of the 
optical axis of the principal concave mirror within the tube of the 
reflector telescope. 
Focusing is also possible by making the ocular movable in the direction of 
the optical axis of the light ray path with respect to the principal 
concave mirror. 
For binocular vision two reflector telescopes according to the invention 
can be connected to form a reflector binocular. This way a handy reflector 
binocular with reduced dimensions and weight can be produced with reduced 
optical effort. Thereby, the optic system according to the invention 
affords the choice to construct with considerable cost savings reflector 
binoculars of very small dimensions as well as of larger construction. The 
expense for the mechanical supports is relatively small. 
In addition, the reflector telescope according to the invention can be used 
as an amateur reflector telescope or as a teleobjective for cameras.

SPECIFIC DESCRIPTION 
FIG. 1 shows in a schematic representation an embodiment of the reflector 
telescope S according to the invention in a projection on a plane of a 
longitudinal section containing the optical axis of the principal mirror 
and FIG. 2 shows the same reflector telescope in projection on a cross 
sectional plane. 
The reflector telescope according to the invention is related as to 
function to the terrestrial lens telescope and the classical Gregorian 
telescope. In the case of the terrestrial lens telescope, the refractive 
power of the objective and the refractive power of the reversing system 
are achieved through refractive lenses; in the case of the Gregorian 
telescope both are achieved through concave mirrors. 
The reflector telescope according to the present invention is 
distinguishable from the classical Gregorian telescope by a double folding 
of the light ray path between the principal and reversing mirrors with the 
aid of two plane mirrors, whereby, with regard to the size of the field of 
vision and the image quality a new degree of freedom is achieved as to the 
diameter and the focal distance of the reversing mirror. 
According to FIG. 1, the light coming for instance from an infinetely 
remote axial object point (from left according to FIG. 1) can first pass 
through a non-refractive anti-pollution plane-parallel plate 1, which 
according to the embodiment--also see now FIG. 2--carries in its central 
portion the collector mirror 2, and then falls on a principal mirror 3 
built as a concave mirror situated at the rear end of the telescope 
housing (tube) 12, this principal mirror having for instance a diaphragm 
index of 2.0 and the boundary defining the entry pupil 4 the light ray 
path being then collected in the direction of the focal point of the 
principal mirror 3, the site of the first real intermediate image. Before 
the light reaches the location of the intermediate image 5, the light ray 
paths are deflected by a collector mirror 2, whose diameter (in the 
projection on a plane perpendicular to the axis) corresponds to 
approximately 2/5 of the diameter of the telescope housing 12, this 
deflection taking place at an angle of approximately 60.degree. with 
respect to the optical axis of the principal mirror 3; then, after passing 
the location of the first real intermediate image 5', the light ray path 
hits the plane folding mirror 6, which is only slightly inclined with 
respect to the telescope housing 12, this mirror deflecting again the path 
of the light rays and thereby the optical axis, so that it runs almost 
perpendicular to the optical axis of the principal mirror 3, but laterally 
displaced. 
After this double folding of the light ray path by the collector mirror 2 
and the folding mirror 6, the light reaches the reversing mirror 7 which 
is laterally shifted with respect to the longitudinal sectional plane of 
the telescope housing 12 by approximately half of its diameter, so that 
the optical axis reflects itself. 
As a result, the light ray path retraces its course first to the folding 
mirror 6, located in the vicinity of the wall of the telescope housing 12 
and from there, after running through a real intermediate image of the 
entry pupil 8, is focused by the collector mirror 2 in the direction of 
the optical axis of the principal mirror 3 to form the second real upright 
image 9 in the vicinity of the principal mirror 3, which image is observed 
through an ocular consisting in principal of the field lens 10 and the 
eyelens 11. The ocular is of the usual multilens construction for the 
angle of view. The refracting power of the field lens 10 decides the 
location of the real exit pupil 14. An opaque conical tube 13 in the shape 
of a frustoconical casing serves as a protection means or shield against 
infiltrated light. 
In comparison with the Gregorian telescope, due to the arrangement of the 
collector mirror 2, the folding mirror 6 and the reversing mirror 7 in the 
path of the light rays and with respect to the telescope housing 12, the 
image ray path is folded six times in the reflector telescope S (in the 
Gregorian telescope only two times), and namely twice between the 
principal mirror 3 and the reversing mirror 7, twice between the reversing 
mirror 7 and the principal mirror 3, in addition to the folding that takes 
place at the principal mirror 3 and the reversing mirror 7 corresponding 
to the folding in the Gregorian telescope. 
In this embodiment of the reflector telescope according to the invention, 
the presence of the anti-contamination plane-parallel plate 1 within the 
optical system according to the invention is not absolutely necessary. It 
represents here only a sealing device against dirt penetration and can 
therefore be constructed as a plane-parallel, non-refractive glass plate. 
It can also be noted at the same time to carry the collector mirror 2 
mounted appropriately thereon. The principal mirror at the rear end of the 
telescope housing directed towards the eye of the user is a concave 
mirror. The principal mirror 3 is annularly covered with a reflecting 
coating only in the area outwardly of the frustoconical casing 13. In 
order to avoid stress, the central portion of the principal mirror 3 is 
not perforated but integrated in the optical correction system as a 
refracting lens. Through the diffracting radius of the lens in the central 
portion of the principal mirror 3 it is possible, if needed, in 
cooperation with a further lens to provide a focal-distance increasing 
effect in accordance with the principle of the Barlow lens (see FIG. 7). 
The diameter of this central translucent area equals approximately 2/5 of 
the diameter of the (entire) principal mirror 3. 
The principal mirror 3 is centrally and rigidly fastened at the end of the 
telescope housing over the rim 4. The rear surface of the principal mirror 
3 directed towards the eye of the user can be in its central portion, in 
accordance with the optical requirements, either plane or ball-shaped 
(spherical). 
With respect to the path of the light rays, on the other side of the 
principal mirror 3, the ocular consisting of the field lens 10 and the eye 
lens 11 is mounted. The location of the second upright seal intermediate 
image 9 is between the principal mirror 3 and the eye lens 11. It is 
reproduced, as it appears at infinity, by the ocular 10, 11. 
The optical axes of the principal mirror 3 and the ocular 10, 11 coincide, 
being thus centered with respect to each other. 
The collector mirror 2 and the folding mirror 6 are preferably constructed 
as plane-surface mirrors, in order to eliminate aberrations which would 
occur in spherical surfaces. In the optical sense, therefore, the light 
ray path remains axially symmetrical. 
Further, the collector mirror 2 is preferably an elliptical collector 
mirror with regard to its boundaries; it is rigid except when it is part 
of a slidable construction group, to which will be referred in greater 
detail later. The perpendicular to the collector mirror 2 is inclined by 
approximately 60.degree. with respect to the optical axis of the principal 
mirror 3. 
The plane folding mirror 6 is rigidly mounted, except when it is part of a 
slidable construction group, which will be referred to later. 
The reversing mirror 7 is constructed as collecting concave mirror. The 
optical axis of the reversing mirror 7 can be perpendicular to the axis of 
the principal mirror 3. In the embodiment shown in FIG. 1, the reversing 
mirror 7 is laterally displaced with respect to the perpendicular plane 
containing the optical axis of the principal mirror by approximately half 
of its diameter. This arrangement of the reversing mirror mirror has the 
purpose to maintain such a short distance between the collector mirror 2 
and the frontal opening of the protection cone 13 as to eliminate the 
possibility of light infiltrations coming from the object side passing the 
collector mirror and the inner space of the protection cone 13, thus 
reaching the second real intermediate image 9. The angle made by the 
collector mirror 2 and the folding mirror 6 necessarily derives from the 
afore-mentioned arrangement of the reversing mirror 7. 
In FIG. 1, the folding mirror 6 and the reversing mirror 7 are almost 
tangential to the telescope housing 12, or in other words, they extend as 
little as possible into the parallel path of the light rays as defined by 
the principal mirror 3. Also when it comes to binocular embodiments, the 
space required by the reversing mirror 7 outside the telescope housing 12 
does not create any disadvantages. The reversing mirror 7 constructed as a 
concave mirror can be movable in the direction of its optical axis. (in 
the course of this motion, no tilting is allowed, since the image would 
become inclined to the optical axis). Due to the movability of the 
reversing mirror 7 in the direction of its optical axis an inner focusing 
for the distance adjustment takes place in the telescope housing 12. 
The collector mirror 2, the folding mirror 6 and the reversing mirror 7 can 
also be rigidly connected to each other forming a construction group which 
is slidable within the telescope housing 12 in the direction of the 
optical axis of the principal mirror 3. With the aid of this group the 
user can make sharp adjustments of the respective distance of an object, 
through focusing. 
Also for the purpose of focusing, the ocular 10, 11 can be made movable in 
the direction of the optical axis of the path of the light rays so that 
the focusing can be done by moving the ocular in axial direction with 
respect to the principal mirror 3. 
The size of the mirror surfaces of the principal mirror 3, the collector 
mirror 2, the folding mirror 6 and the reversing mirror 7 is determined by 
taking into consideration the field of vision selected for the 
construction, whereby one can use for this purpose as auxiliary means a 
representation of the light ray path in evolute form. 
The spacings of the mirrors with respect to each other is determined when 
the diameter of the principal mirror 3, or its aperture ratio is 
established and sets the diameter of the telescope housing 12. If the path 
of the light ray is here also represented in evolute form, then the 
reversing mirror 7 is located somewhere in the middle between the 
principal mirror 3 and the second real upright intermediate image 9 in 
front of the ocular 10, 11. The distance between the folding mirror 6 and 
the reversing mirror 7 is approximately indicated by the diameter of the 
telescope housing 12. The distance between the collector mirror 2 and the 
folding mirror 6 is in a projection on a telescope cross section basically 
somewhat larger than the radius of the telescope housing 12. The collector 
mirror 2 with elliptical rim is centered to the optical axis of the 
principal mirror, but inclined to the degree required to avoid that the 
light ray path between the collector mirror 2 and the folding mirror 6 and 
the light ray path between the folding mirror 6 and the reversing mirror 7 
is not being vignetted due to the protection cone 13. 
The radius of the principal mirror is equal to the double of its focal 
distance. The focal distance of the reversing mirror is calculated 
according to the formula 
##EQU1## 
wherein 00' is given by the sum of the distances of the reversing mirror 7 
from the object and the image and .beta. being equal to the image 
dimension of the reversing mirror 7. 
The image dimension of the reversing mirror 7 lies in the range of 
.beta.=-2.3 to .beta.=-3.5, preferably in the range of .beta.=-2.5 to 
.beta.=-3.3. 
Since the reversing mirror does not obstruct the path of the light rays, it 
is possible to increase its diameter as well as to lengthen the focal 
distance of the reversing mirror. The possible increase in the size of the 
reversing mirror is advantageous for the size of the field of vision and 
the typical value of the image size in the range of .beta.=-2.5 up to 
.beta.=-3.3 means a reduced ellipticity of the reversing mirror and 
thereby reduced image aberrations as well as subsequent smaller 
amplification of the image aberrations of the principal mirror 3. 
Advantageous embodiments of principal mirror 3 and reversing mirror 7 are 
offered when the principal mirror 3 and the reversing mirror 7 are 
spherical surface mirrors, the principal mirror 3 and the reversing mirror 
7 are Mangin-type mirrors or the principal mirror 3 is a parabolic surface 
mirror and the reversing mirror 7 is an elliptical surface mirror. 
The conical tube 13 in the shape of a frustoconical casing is opaque and 
serves for protection against light infiltration. It extends from the 
principal mirror 3 into the telescope housing 12 and can be fastened to 
the principal mirror 3 centrally to the median longitudinal axis of the 
telescope housing 12; it can be cemented to the principal mirror 3 via an 
optical lens or attached to the principal mirror 3 in any suited 
mechanical manner. The inclination of the casing surface of the conical 
tube 13 from the principal mirror 3 to the optical axis (respectively the 
median longitudinal axis of the telescope housing 12) is approximately 
given by a straight line running through the focal point of the principal 
mirror 3 to the center of the intermediate image 5. The conical tube 13 
seen from the eye of the user extends from the principal mirror 3 to the 
intersection of the conical tube 13 with the marginal rays of the median 
pencil of rays between the collector mirror 2 and the principal mirror 3 
up to the area next to the light ray path between the folding mirror 6 and 
the reversing mirror 7. 
The magnification V of the reflector telescope S is given by the formula 
EQU V=-(f.sub.1 .multidot..beta./f.sub.3), 
wherein 
f.sub.1 is the focal distance of the principal mirror 3 and 
f.sub.3 the focal distance of the ocular 10, 11. 
On the other hand, the diameter of the exit pupil 14 is the quotient of the 
diameter of the principal mirror 3 and the magnification V. 
The total focal distance of the reflector telescope S resulting from the 
concave principal mirror 3 and the reversing mirror 7 can be lengthened 
substantially by a subsequently added Barlow lens 15 as seen in FIG. 7. 
To the optical system basically consisting of concave principal mirror 3 
and the reversing mirror 7 a lens system with variable image size can also 
be added. 
Further, the reversing mirror 7 can be cardanically suspended to be 
tiltable, with the aid of motorized means and sensor control, around two 
axes, perpendicular to each other and perpendicular to the optical axis of 
the reversing mirror 7 for the compensation of the tilting motions of the 
reflector telescope with respect to the eye of the observer. 
The drawing according to FIGS. 3 and 4 and FIG. 5 show in schematic 
representation binocular embodiments, in each of them two reflector 
telescopes (S.sub.1, S.sub.2) are connected into a reflector binocular for 
binocular vision with, in both cases (FIG. 3, FIG. 4 and FIG. 5) with a 
tenfold magnification. 
FIGS. 3 and 4 show a binocular S.sub.1, S.sub.2 for binocular vision at a 
scale 1:1 of an actual embodiment. The construction of each of these 
reflector telescopes corresponds to the construction of the reflector 
telescope S in FIGS. 1 and 2 and therefore similar parts in FIGS. 3 and 4 
are marked with the same reference numerals as in FIGS. 1 and 2. In the 
case of the reflector binocular according to FIGS. 3 and 4 the 
interpupillar distance in the normal one of 62 mm and the diameter of the 
exit pupil is of 3.5 mm, almost as the one in the common 8.times.30 
field-glass magnifier. In comparison with a fieldglass magnifier with a 
prismatic reversing system and tenfold magnification the advantageous 
dimensions appear clearly. 
The fact that in the drawing the two reflector telescopes S.sub.1 and 
S.sub.2 are shown one on top of the other makes possible a top-view 
projection and a cross-sectional projection of a reflector telescope. Both 
reflector telescopes S.sub.1 and S.sub.2 each of them corresponding to one 
eye of the user are symmetrically of identical construction, whereby the 
upper reflector telescope S.sub.1 corresponds to the right eye and the 
lower telescope S.sub.2 to the left one of the user. In this embodiment, 
both reversing mirrors 7 which are larger than the folding mirrors 6 are 
located in the vicinity of the theoretical median usage position (with the 
bridges connecting the two reflector telescopes) of the reflector 
binocular, so that the rim of the reversing mirror which extends somewhat 
beyond the cylindrical housing 12 of the telescope does not influence its 
appearance. The light ray paths in the partial telescopes S.sub.1, S.sub.2 
are axially symmetrical in the optical sense. 
Also in the case of such a reflector binocular for binocular vision 
focusing is possible. The reversing mirror 7 of both reflector telescopes 
S.sub.1, S.sub.2, in the afore-described arrangement, can be arranged so 
that their focusing movements run parallel, facilitating thereby the use 
of particularly simple mechanical means. 
The necessary adjustments of the reversing mirror 7 are very small, because 
the influence on the position of the second real intermediate image is a 
function of the square of the size of the partial image of the reversing 
mirror 7. 
A further focusing possibility existing in the reflector binocular is 
created by the fact that each construction assembly comprising the 
reversing mirror 7 and also the collector mirror 2 and the folding mirror 
6 is slidable in the direction of the optical axis of the principal mirror 
3 relatively to the principal mirror 3. 
Finally, the oculars can also be displaced relatively to each of the 
principal mirrors 3 for the purpose of focusing. 
In addition to FIGS. 3 and 4 the above description can also make reference 
to the FIGS. 1 and 2. 
In FIGS. 5 and 6 also an embodiment of a reflector binocular consisting of 
two reflector telescopes S.sub.1, S.sub.2 for binocular vision and tenfold 
magnification in day light is shown and namely at a scale 1:1 an 
embodiment taken from the practice, from which it becomes clear how 
compact and handy this type of construction can be. The representation of 
FIGS. 5 and 6 is scaled down by a factor 1.4 in comparison to FIGS. 3 and 
4. Otherwise, in FIGS. 5 and 6 the same parts are marked with the same 
reference numerals as in FIGS. 3 and 4, so that reference can be made to 
the embodiments of FIGS. 3 and 4 and further to the embodiments of FIGS. 1 
and 2. 
The reflector telescope according to the invention can therefore be used 
especially in optical systems for binocular vision, but also in the field 
of the amateur reflector telescope, whereby the upright image is very much 
appreciated by the amateur. Further, the use as a teleobjective for 
photographic cameras appears advantageous. 
The large number of foldings of the light ray path in the reflector 
objective according to the invention as part of the reflector telescope 
creates the possibility for very reduced typical overall dimensions of 
approximately 30% of the total focal distance. When used as a micro-image 
objective, an approximate focal distance of 600 mm can be achieved with a 
construction height of 180 mm. 
When the reflector telescope according to the invention is used as an 
amateur telescope with a 50 to 100-fold magnification in a monocular 
instrument the reduced constructive dimensions are very advantageous due 
to the reduced weight and the comparatively small space requirement 
derived therefrom. 
The magnification of the reflector telescope can be increased for binocular 
observation during day light because of the normal pupillar distance of 62 
mm up to approximately 25-fold magnification, when an exit pupil diameter 
of approximately 2 mm is sufficient. This results forcibly in the case of 
the construction with rectilinear vision. 
Special binocular constructions for twilight vision are limited to ten- to 
twelve-fold magnification because of the required diameter of 
approximately 5 mm of the exit pupil.