Observation instrument for observing a celestial body

Abstract

Observation instrument (10) for observing a celestial body (12) with • an entrance plane (18) with an entrance slit (20) for admitting at least part of a celestial body image, • an image generating device (22) for generating the celestial body image on the input plane (18), wherein the image generating device (22) comprises a first reflection element (26), • a scanning axis (24), wherein the first reflection element (26) is arranged such that it can be tilted about the scanning axis (24) that a relative movement between the celestial body image and the input plane (18) can be generated by tilting the first reflection element (26) about the scanning axis (24).

Description

[0001] The invention relates to an observation instrument for observing a celestial body.

[0002] Spectroheliographs are one of the observation instruments used to observe the sun. A spectroheliograph produces a monochromatic image of the sun. Sunlight passes through the lens of a telescope onto an entrance slit of the spectroheliograph, creating an image of the sun at the entrance slit. A narrow section of the sun's image passes through the entrance slit and is split into its spectral lines, for example, by a diffraction grating. By isolating one of the spectral lines using a photographic plate, a monochromatic image of that section of the sun's image can be created. In newer designs of the spectroheliograph, the photographic plate is often replaced by an electronic image sensor. This is known, for example, from US Pat. No. 7,209,229 B2.

[0003] In order to capture not just a section of the solar image but the entire solar image, it is necessary to move the solar image evenly across the entrance slit. This type of movement of a celestial body image across the observation instrument is also called "scanning." It is essential to coordinate the speed of movement of the celestial body image with the photographic plate or electronic image sensor. To simplify coordination, a constant speed of movement between the observation instrument and the celestial body image is preferably selected.

[0004] The simplest way to move the celestial body image across the observation instrument is to utilize the Earth's rotation and thus the natural movement of the celestial body image relative to a stationary observation instrument on Earth. The disadvantage of this approach, however, is the relatively long runtime for the complete celestial body image to be transferred across the observation instrument.

[0005] To be independent of the natural movement of the celestial body image due to the Earth's rotation, various techniques have been developed, using the spectroheliograph as an example. In these techniques, a fixed solar image is first generated using a coelostat or heliostat, and then a controllable relative movement between the entrance slit and the solar image is created. In the Meudon and Coimbra observatories, for example, the telescope objective located between the coelostat and the entrance slit is shifted. US 2011 / 0 051 121 A1 describes a shift of the entrance slit.

[0006] The disadvantage of the known arrangements and methods for moving the celestial body image over the observation instrument is that they are very slow and / or the quality of the image is unsatisfactory.

[0007] The invention is therefore based on the object of providing an observation instrument for observing a celestial body which overcomes these disadvantages and is also easy to manufacture and operate and has a compact design.

[0008] The object is achieved according to the invention by an observation instrument having the features of patent claim 1.

[0009] Advantageous embodiments and further developments of the invention are specified in the dependent claims.

[0010] An observation instrument according to the invention for observing a celestial body comprises an entrance plane with an entrance slit for admitting at least part of a celestial body image, an image generation device for generating the celestial body image on the entrance plane, wherein the image generation device comprises a first reflection element, and a scanning axis. The first reflection element is arranged so as to be tiltable about the scanning axis that a relative movement between the celestial body image and the entrance plane can be generated by tilting the first reflection element about the scanning axis. This allows the celestial body image to be moved across the entrance slit. Furthermore, by means of such an arrangement, a scanning device can be provided in a small installation space and a high-quality celestial body image can be generated. The first reflection element is preferably arranged so as to be tiltable when installed in the observation instrument.This allows the first reflection element to be movable during the intended use of the observation instrument. The first reflection element can be arranged on the scan axis such that it is intersected by the scan axis. Preferably, the first scan axis runs through the apex of the curvature of the first reflection element. This ensures that neither the focal length nor the focal point shifts along a first optical axis of the first reflection element upon tilting. The optical axis is preferably the axis that runs through the center of an optical effective surface of the corresponding reflection element and is aligned orthogonally to the optical effective surface at the center.

[0011] The speed at which the celestial body image is moved across the entrance slit can thus depend, in particular, on the speed at which the first reflection element is tilted around the scan axis. The first reflection element is preferably arranged in the beam path of the light emitted by the observed celestial body and incident on the entrance plane.

[0012] The light emitted by the observed celestial body can strike the first reflection element directly. Alternatively, the observation instrument can be combined with a compensation device arranged in the beam path of the light emitted by the observed celestial body, between the observed celestial body and the first reflection element. By means of such a compensation device, the light emitted by the observed celestial body can be directed onto the first reflection element. The compensation device can be designed, in particular, to compensate for the relative movement between the celestial body image and the observation instrument caused by the Earth's rotation. The compensation device can be arranged, in particular directly, on the observation instrument. The compensation device can be designed, for example, as a heliostat or celost. The observation instrument is preferably designed as a helioscope.

[0013] The image generation device is preferably arranged in an instrument housing of the observation instrument. This allows the observation instrument to be compact and easily transportable. The first reflection element can be mounted so as to be rotatable about the scanning axis relative to the instrument housing. The image generation device is preferably arranged entirely within the instrument housing. The observation instrument preferably has precisely one instrument housing, in which the entire observation instrument is particularly preferably arranged. Furthermore, the compensation device can be arranged within the instrument housing.

[0014] In particular, if the image generation device is arranged in the instrument housing of the observation instrument, the observation instrument can be designed to be portable. The observation instrument is referred to here and below as portable if, due to its shape and weight, it can be carried by an average adult. For this purpose, the observation instrument has a mass of preferably 30 kg or less. This can simplify transport and significantly expand the range of applications of the observation instrument. In one embodiment of the invention, the mass of the observation instrument can be in the range of 20 to 30 kg. The observation instrument preferably has a length of approximately 2 m. In a further embodiment of the invention, the mass of the observation instrument can be in the range of 8 to 10 kg. The observation instrument preferably has a length of approximately 90 cm.

[0015] The scan axis is preferably arranged such that the celestial body image can be moved orthogonally to the entrance slit by tilting the first reflection element about the scan axis. The scan axis is particularly preferably arranged parallel to the entrance slit. Alternatively, the scan axis can be arbitrarily oriented with respect to the entrance slit, and a deflection element can be arranged in the beam path between the first reflection element and the entrance plane. The deflection element can deflect the light emanating from the first reflection element such that, even when the scan axis is arranged non-parallel to the entrance slit, tilting the first reflection element about the scan axis causes the celestial body image to move orthogonally to the entrance slit. This configuration is preferably described such that the scan axis is arranged mechanically non-parallel but optically parallel to the entrance slit.The orthogonal movement of the celestial body image across the entrance slit can facilitate the recording of the individual sections of the celestial body image falling through the entrance slit and their subsequent composition into an overall image.

[0016] In a preferred embodiment of the invention, the first reflection element is concave, in particular spherically concave.

[0017] Alternatively, the first reflection element can be convex, in particular spherically convex. Such an embodiment of the first reflection element is preferably used when the first reflection element is in optically operative connection with other optical elements, in particular the image-generating device.

[0018] The first reflection element can have a first focal point due to its concave or convex configuration. The first reflection element can thus assume a function not only with regard to the movement of the celestial body image across the entrance slit but also with regard to the generation of the celestial body image on the entrance slit.

[0019] The terms "concave" and "convex" used here and below preferably describe the shape of an optical effective surface of the corresponding reflection element, onto which the incident light impinges. The term "spherical" here and below preferably refers to the optical effective surface of the corresponding reflection element. With a spherical design of the reflection element, the concave or convex effective surface preferably has a constant radius of curvature. As an alternative to a spherical cross-section, each of the optical concave or convex effective surfaces described here and below can have a conical, in particular a parabolic, elliptical, or flattened elliptical, cross-section. Spherical surfaces can have the advantage of being cost-effective to produce.In addition, they can be easy to center because their radius of curvature is constant, unlike, for example, a surface with a parabolic cross-section.

[0020] In a particularly preferred embodiment of the invention, the image-generating device has a second reflection element that is in optically operative connection with the first reflection element. The operative connection is preferably designed such that a second optically active surface of the second reflection element faces a first optically active surface of the first reflection element. The first reflection element and the second reflection element are preferably referred to as facing one another if they are arranged such that light incident on the first reflection element can impinge directly on the second reflection element after being reflected by the first reflection element, i.e. without further deflection. The second reflection element can be arranged on the first optical axis. In this way, the light incident on the first reflection element can be reflected to the second reflection element.The angle of incidence at which the incident light strikes the second reflection element is typically equal to the angle at which the light reflected by the second reflection element bounces off the second reflection element. The effect of the tilting of the first reflection element on the celestial body image generated on the input plane can thereby be doubled. As a result, in the presence of the second reflection element, halving the tilt angle of the first reflection element can produce the same movement of the celestial body image on the input plane compared to an embodiment without the second reflection element. The first and / or the second reflection element are preferably each designed as a mirror.

[0021] Furthermore, the optical interaction of the first reflection element with the second reflection element allows the focusing of the celestial body image within the image generation device to be distributed across multiple instances. This allows the heat introduced into the observation instrument by the light from the celestial body image to be more evenly distributed and thus more effectively dissipated. Furthermore, the arrangement of the second reflection element around at least one additional scanning axis is conceivable.

[0022] The second reflection element is preferably convex, in particular spherically convex. Such a design of the second reflection element is preferably used in combination with a concave, including spherically concave, design of the first reflection element. Alternatively, the second reflection element can be concave, in particular spherically concave, or flat. The second reflection element can have a second focal point if it is concave or convex. In the case of a concave or convex design of one of the reflection elements, the corresponding optical axis preferably runs as a normal through a vertex of curvature of the respective reflection element.

[0023] Preferably, the Petzval sum of the image generation device is 0. As a result, the celestial body image generated on the input plane exhibits no image curvature. Preferably, the optical effective surface of the first reflection element and the optical effective surface of the second reflection element have the same or nearly the same radii of curvature. Thus, the Petzval sum of 0 can be realized exclusively with the first reflection element and the second reflection element.

[0024] The second reflection element can be arranged in an incident beam path of the first reflection element. The incident beam path is understood here and below to be the area through which light falls onto the optical effective surface of the corresponding reflection element. Such an arrangement allows for a geometrically simple design of the image-generating device.

[0025] The first reflection element can have a passage opening for an outgoing beam path of the second reflection element. Here and below, the outgoing beam path is preferably understood to be the area through which light emanating from the optical effective surface of the corresponding reflection element passes. Such an arrangement allows the outgoing beam path of the second reflection element to impinge on the input plane.

[0026] In a preferred embodiment of the invention, the image generation device is designed as a mirror optics system. The optical elements that have a significant influence on the image quality or the image scale are therefore preferably designed as essentially reflective elements. This makes it possible to generate a high-quality image of a celestial body on the input plane, the quality of which is not significantly impaired, in particular by the wavelength or the angle of the incident light. Preferably, the first reflection element and the second reflection element are each designed as a mirror. The image generation device designed as a mirror optics system can comprise at least one field lens, which is preferably arranged in the beam path close to the input plane. This allows an exit pupil of the image generation device to be imaged onto an entrance pupil of the collimating objective.The at least one field lens usually has no significant influence on the image quality or the image scale.

[0027] The observation instrument may comprise a spectrograph for dispersing light entering through the entrance slit into spectral lines. The observation instrument may thus be designed, in particular, as a spectroheliograph. The spectrograph may, in particular, have a diffraction grating for dispersing the incident light.

[0028] Furthermore, the observation instrument can comprise at least one electronic image sensor for detecting at least one of the spectral lines. By detecting at least one of the spectral lines, the electronic image sensor can create a monochrome image of the portion of the celestial body image passing through the entrance slit. Using an electronic image sensor, the spectral line to be recorded can be easily selected and further processed electronically.

[0029] The image generation device is preferably correlated with the at least one electronic image sensor. The images taken by the at least one image sensor are generally composed of several individual images of each of the parts of the celestial body image passing through the entrance slit. By correlating the image generation device with the at least one image sensor, the function of the at least one image sensor and movement around the scan axis can be coordinated. The correlation is particularly advantageous with regard to the frequency at which the at least one image sensor takes the individual images and the order in which the individual images are combined to form an overall image of the celestial body image. In a simple case, the correlation can be purely temporal. The starting time and / or the speed of the tilting around the scan axis are known to the at least one electronic image sensor.The individual images can then be assembled by a computer, particularly based on these parameters. An electronic coupling of the movement around the at least one scanning axis and the at least one electronic image sensor is not required for this purpose. Preferably, the image generation device and the at least one electronic image sensor are electronically coupled to one another, particularly preferably by means of an electronic data processing unit.

[0030] In a preferred embodiment of the invention, the at least one electronic image sensor is arranged immovably relative to the spectrograph. This allows the observation instrument to be manufactured in a structurally simpler and more cost-effective manner. The at least one electronic image sensor preferably has a first dimension and a second dimension. The at least one image sensor can be arranged such that the at least one spectral line output by the spectrograph is aligned along the first dimension. If multiple spectral lines are output by the spectrograph, the spectral lines can be arranged parallel to one another in the direction of the second dimension. The first dimension of a detected spectral line can thus contain location information about the detected content. The second dimension of a detected spectral line can contain color information about the detected content.The selection of one of the at least one spectral line to be detected, falling at any point on the at least one image sensor, and its arrangement in the overall image of the celestial body can be carried out electronically.

[0031] The at least one electronic image sensor can be designed as a line sensor. This allows the installation space required by the at least one electronic image sensor to be reduced and the observation instrument to be manufactured more cheaply. The use of a line sensor can also reduce the computational effort required to create the image of the celestial body. The line sensor is preferably arranged parallel to the at least one spectral line output by the spectrograph such that the at least one spectral line to be detected falls on the line sensor. The line sensor is thus preferably arranged along the first dimension. The selection of the at least one spectral line to be detected can thus be made by arranging the line sensor along the second dimension. The additional acquisition of color information is therefore not necessary to create a monochrome image.A line sensor is therefore sufficient to create a monochromatic image of celestial bodies.

[0032] The image generation device preferably has an electronic interface. In addition, the spectrograph and / or the at least one electronic image sensor, in particular, can have an electronic interface. The electronic interface of the spectrograph is preferably arranged on the diffraction grating. The diffraction grating can be arranged displaceably, in particular rotatably, relative to the entrance slit or the collimation lens, in particular for adjusting the wavelength. Thus, in particular, the wavelength of the diffraction grating can preferably be adjusted using the electronic interface of the spectrograph.

[0033] The focusing of the observation instrument can be achieved by changing the arrangement, in particular the distance, of the respective components to each other in at least one of the following component pairs: • Image forming device - entrance slit, • Collimation lens - entrance slit, • Camera lens - image sensor.

[0034] Preferably, the focus is adjustable via the electronic interface of at least one of the corresponding components. In particular, at least one of the following components can also have the electronic interface: entrance slit, collimation lens, camera lens.

[0035] The electronic interface is preferably designed as an ASCOM interface. The ASCOM interface is a standardized software interface for astronomical equipment. This allows electronic communication between the individual components to take place via a standardized software interface, thus facilitating communication. Operation of the system using a central computer, which particularly preferably also has an ASCOM interface, is also significantly simplified. It is particularly advantageous if the spectrograph has an ASCOM interface. The ASCOM interface of the imaging device preferably comprises an ASCOM interface of the scan axis.

[0036] An embodiment of the invention is explained with reference to the following figures. It shows: Fig. 1 a schematic representation of an observation instrument with a first reflection element and a second reflection element, Fig. 2a a schematic representation of the reflection elements of the Fig. 1 in a non-tilted position of the first reflection element, Fig. 2b a schematic representation of the reflection elements of the Fig. 1 in a tilted position of the first reflection element.

[0037] The Fig. Figures 1 to 2b show various views of an embodiment. For clarity, not all reference numerals are used in each figure.

[0038] Fig. 1 shows a schematic representation of an observation instrument 10 for observing a celestial body 12, namely a sun 14. The observation instrument 10 is preferably designed as a spectroheliograph 16. The observation instrument 10 comprises an entrance plane 18 with an entrance slit 20 for admitting at least part of a celestial body image, an image generation device 22 for generating the celestial body image on the entrance plane 18, and a scan axis 24. The image generation device 22 has a first reflection element 26, which is arranged such that it can be tilted about the scan axis 24 that a relative movement between the celestial body image and the entrance plane 18 can be generated by tilting the first reflection element 26 about the scan axis 24. This allows the celestial body image to be moved across the entrance slit 20. The scan axis 26 can intersect the first reflection element 26.

[0039] The Fig. 2a and Fig. 2b clearly show the effect of tilting the first reflection element 26. While in the first, in Fig. 2a shown position of the first reflection element, the light 28 producing the celestial body image falls centrally on the input plane 18, the light 28 hits Fig. 2b, which shows the first reflection element 26 in a second, differently tilted position, at a different location on the input plane 18.

[0040] The speed at which the celestial body image is moved across the entrance slit 20 can thus depend, in particular, on the speed at which the first reflection element 26 is tilted about the scan axis 24. The first reflection element 26 is preferably arranged in the beam path 30 of the light 28 emitted by the observed celestial body 12 and incident on the entrance plane 18.

[0041] How Fig. As shown in Figure 1, the observation instrument 10 can be combined with a coelostat 32 to compensate for the relative movement between the celestial body image and the observation instrument caused by the Earth's rotation. The coelostat 32 can comprise a first reflector 33a and a second reflector 33b. The coelostat 32 can be arranged in the beam path 30 of the light 28 emitted by the observed celestial body 12, between the observed celestial body 12 and the first reflection element 26.

[0042] The Fig. The imaging device 22 shown in Figure 1 is arranged in an instrument housing 34 of the observation instrument 10. The first reflection element 26 is mounted so as to be rotatable about the scanning axis 24 relative to the instrument housing 34.

[0043] The scanning axis 24 is arranged mechanically and optically parallel to the entrance slit 20. By tilting the first reflection element 26, the celestial body image can be guided across the entrance slit 20. This can facilitate the recording of the individual sections of the celestial body image passing through the entrance slit 20 and their subsequent combination into an overall image.

[0044] As is especially evident from Fig. 2a and Fig. As can be seen from Figure 2b, the first reflection element 26 is spherically concave. Due to the concave shape, the first reflection element 26 may have a first focal point (not shown).

[0045] The Fig. The image-generating device 22 shown in Figures 1 to 2b has a second reflection element 38 that is in optically operative connection with the first reflection element 26. The operative connection is preferably configured such that a second optically operative surface 40 of the second reflection element 38 faces a first optically operative surface 42 of the first reflection element 26. The second reflection element 38 can be arranged on a first optical axis 36. In this way, the light 28 incident on the first reflection element 26 can be reflected to the second reflection element 38. The first optical axis 36 runs as a normal through the apex of curvature of the first reflection element.

[0046] The angle of incidence at which the incident light 28 strikes the second reflection element 38 is typically equal to the rebound angle at which the light 28 reflected by the second reflection element 38 bounces off the second reflection element 38. The effect of the tilting of the first reflection element 26 on the celestial body image generated on the input plane 18 can thereby be doubled. As a result, in the presence of the second reflection element 38, halving a tilt angle 44 can produce the same movement of the celestial body image on the input plane 18 compared to an embodiment without the second reflection element. The tilt angle 44 preferably describes the angle between the first optical axis 36 in a tilted position of the first reflection element 26 and the first optical axis in a non-tilted position of the first reflection element 26 (see Fig. 2b). Preferably, in a non-tilted position of the first reflection element 26, the first optical axis 36 and a second optical axis of the second reflection element 37 lie on top of each other or parallel to each other (see Fig. 2a, Fig. 2b).

[0047] The second reflection element 38 is spherically convex. The first reflection element 26 and the second reflection element 38 are preferably configured such that the image curvature is compensated for by the combination of the concave first reflection element 26 and the convex second reflection element 38. The Petzval sum of the image generation device is thus preferably 0. The celestial body image generated on the input plane 18 therefore preferably exhibits no image curvature.

[0048] As in Fig. 1, the second reflection element 38 is arranged in an incident beam path 46 of the first reflection element 26. The first reflection element 26 preferably has a passage opening 48 for an outgoing beam path 50 of the second reflection element 38, so that the outgoing beam path 50 of the second reflection element 38 can impinge on the input plane 18. With the first reflection element 26 and the second reflection element 38, the optical elements that have a significant influence on the image quality or the image scale are designed as reflective elements. In the Fig. In the embodiment shown in Figures 1 to 2b, the image generating device 22 is thus designed as a mirror optic.

[0049] As in Fig.1, the observation instrument 10 can comprise a spectrograph 52 for dispersing light 28 incident through the entrance slit 20 into spectral lines 53. The observation instrument 10 can thus be designed as a spectroheliograph 16. To disperse the incident light 28, the spectrograph 52 can, in particular, have a reflective diffraction grating 54. The spectrograph 52 preferably also comprises a collimation lens 56 through which the light 28 passes before impinging on the diffraction grating 54.

[0050] Furthermore, the observation instrument 10 can comprise at least one electronic image sensor 58 for detecting at least one of the spectral lines 53. A camera lens 60 is preferably arranged between the diffraction grating 54 and the electronic image sensor 58. By detecting at least one of the spectral lines 53 by the electronic image sensor 60, a monochrome image of the part of the celestial body image passing through the entrance slit 20 can be created.

[0051] Preferably, the image generation device 22 is correlated with the electronic image sensor 58. For this purpose, the image generation device 22 and the electronic image sensor 58 can be coupled to one another by means of an electronic data processing unit 62. The images taken by the image sensor 58 are generally composed of several individual images of the parts of the celestial body image passing through the entrance slit 20. By correlating the image generation device 22 with the image sensor 58, the function of the image sensor 58 and movement about the scan axis 24 can be coordinated. The correlation is particularly advantageous with regard to the frequency at which the image sensor 58 takes the individual images and the order in which the individual images are combined to form an overall image of the celestial body image.

[0052] The electronic image sensor 58 is arranged immovably relative to the spectrograph 52. The electronic image sensor 58 preferably has a first dimension 64 and a second dimension 66. The image sensor 58 is preferably arranged such that the spectral lines 53 output by the spectrograph 52 are aligned along the first dimension 64. In the direction of the second dimension 66, the spectral lines 53 can be arranged parallel to one another. The first dimension 64 of one of the detected spectral lines 53 can thus contain location information about the detected content. The second dimension 66 of one of the detected spectral lines 53 can contain color information about the detected content.The selection of one of the spectral lines 53 to be detected, which fall at any point on the image sensor 58, and its arrangement in the overall recording of the celestial body image can be carried out electronically, in particular by means of the electronic data processing unit 62.

[0053] The image generation device 22 preferably has an electronic interface. In addition, in particular, the spectrograph 52 and / or the at least one electronic image sensor 58 can have an electronic interface. The electronic interface of the spectrograph 52 is preferably arranged on the diffraction grating 54. The diffraction grating 54 can be arranged displaceably, in particular rotatably, relative to the entrance slit 20 or the collimation lens 56, in particular for adjusting the wavelength. Thus, in particular, the wavelength of the diffraction grating 54 can preferably be adjusted by means of the electronic interface of the spectrograph 52.

[0054] The focusing of the observation instrument 10 can be achieved by changing the arrangement, in particular the distance, of the respective components to each other in at least one of the following component pairs: • Image forming device 22 - entrance slit 20, • Collimation lens 56 - entrance slit 20, • Camera lens 60 - Image sensor 58.

[0055] Preferably, the focus is adjustable via the electronic interface of at least one of the corresponding components. In particular, at least one of the following components can also have the electronic interface for this purpose: entrance slit 20, collimation lens 56, and camera lens 60. The electronic interface is preferably designed as an ASCOM interface. List of reference symbols 10 Observation instrument 12 celestial bodies 14 Sun 16 Spectroheliograph 18 Entrance level 20 Entrance gap 22 Image forming device 24 scan axis 26 first reflection element 28 light 30 Beam path 32 Celostat 33a first reflector 33b second reflector 34 instrument housings 36 first optical axis 37 second optical axis 38 second reflection element 40 second optical effective area 42 first optical effective area 44 tilt angle 46 incident beam path 48 passage opening 50 outgoing beam path 52 spectrograph 53 spectral lines 54 diffraction gratings 56 Collimating lens 58 image sensor 60 camera lens 62 electronic data processing unit 64 first dimension 66 second dimension

Claims

[1] Observation instrument (10) for observing a celestial body (12) with • an entrance plane (18) with an entrance slit (20) for admitting at least part of a celestial body image, • an image generating device (22) for generating the celestial body image on the input plane (18), wherein the image generating device (22) comprises a first reflection element (26), • a scanning axis (24), wherein the first reflection element (26) is arranged such that it can be tilted about the scanning axis (24) that a relative movement between the celestial body image and the input plane (18) can be generated by tilting the first reflection element (26) about the scanning axis (24). [2] Observation instrument according to claim 1, characterized by that the image generating device (22) is arranged in an instrument housing (34) of the observation instrument (10). [3] Observation instrument according to one of the preceding claims, characterized bythat the scanning axis (24) is arranged such that by tilting the first reflection element (26) about the scanning axis (24) the celestial body image can be moved orthogonally to the entrance slit (20). [4] Observation instrument according to one of the preceding claims, characterized by that the first reflection element (26) is concave, in particular spherically concave, or convex, in particular spherically convex. [5] Observation instrument according to one of the preceding claims, characterized by that the image generating device (22) has a second reflection element (38) which is in optical connection with the first reflection element (26). [6] Observation instrument according to claim 5, characterized by that the second reflection element (38) is convex, in particular spherically convex, or concave, in particular spherically concave, or flat. [7] Observation instrument according to one of the preceding claims, characterized by that the Petzval sum of the image generating device (22) is 0. [8] Observation instrument according to one of claims 5 to 7, characterized by that the second reflection element (38) is arranged in an incident beam path (46) of the first reflection element (26). [9] Observation instrument according to one of claims 5 to 8, characterized by that the first reflection element (26) has a passage opening (48) for an outgoing beam path (50) of the second reflection element (38). [10] Observation instrument according to one of the preceding claims, characterized by that the image generating device (22) is designed as a mirror optics. [11] Observation instrument according to one of the preceding claims, characterized by that the observation instrument (10) comprises a spectrograph (52) for decomposing light (28) incident through the entrance slit (20) into spectral lines (53). [12] Observation instrument according to claim 11, characterized by that the observation instrument (10) comprises at least one electronic image sensor (58) for detecting at least one of the spectral lines (53). [13] Observation instrument according to claim 12, characterized by that the image generating device (22) is correlated with the at least one electronic image sensor (58). [14] Observation instrument according to one of claims 12 to 13, characterized by that the at least one electronic image sensor (58) is arranged immovably relative to the spectrograph (52). [15] Observation instrument according to one of the preceding claims, characterized by that the image generating device (22) has an electronic interface.

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