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| themis:technical [2024/12/02 16:36] – etienne | themis:technical [2024/12/13 15:52] (current) – etienne | ||
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| - | ===== THEMIS | + | ===== THEMIS technical description ===== |
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| - | THEMIS is a versatile | + | THEMIS is a versatile |
| - | THEMIS handle the (extremely) wide range of available light energy flux through a dedicated light distribution detailed below. \\ | + | |
| The figure opposite presents a diagram with diverse functional blocks of THEMIS systems. A more realistic cartoon (although simplified) of the light-path within THEMIS is presented hereafter. Below is a description of each of THEMIS functional blocks. \\ | The figure opposite presents a diagram with diverse functional blocks of THEMIS systems. A more realistic cartoon (although simplified) of the light-path within THEMIS is presented hereafter. Below is a description of each of THEMIS functional blocks. \\ | ||
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| - | === 1. Telescope Assembly === | + | ==== 1) Telescope Assembly |
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| + | As a majority of large professional research telescopes, THEMIS is a Ritchey-Chrétien type telescope, with primary and secondary mirrors having hyperbolic shapes. This design allows to eliminate off-axis optical errors (e.g. comatic aberration) and thus offers wider field of view free of optical errors compared to traditional telescope. | ||
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| + | The 90cm primary mirror of THEMIS is made of ... and coated with... | ||
| + | The secondary mirror has a size of and is ... | ||
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| + | The telescope tube has a length of ... | ||
| + | While originally design to be vacuum sealed, the telescope tube is filled with Helium at 0.5 local atmospheric pressure. This enables optimum performance in order to reduce turbulence within the telescope tube and stress on the entrance plate (which would have been excessively important under vacuum conditions. | ||
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| + | The THEMIS telescope is actively cooled by a water heat-exchanger system thanks to... | ||
| + | This allows to have typical working temperature of about 5-10°C on the different system | ||
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| + | The entrance pupil of the THEMIS telescope tube... | ||
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| + | Overall the weight of the THEMIS telescope assembly is about... | ||
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| The telescope optical path has been modified in 2018 to allow for the simplification of the transfer optics F1 -> F2'. The secondary mirror has been refigured, together with a change of the exit window (now an exit lens with optical power and positive chromatic effects). The main resulting characteristics are a new f/16.58 F1 (quite close to the former version), and a new position (lower on) for this focus. \\ | The telescope optical path has been modified in 2018 to allow for the simplification of the transfer optics F1 -> F2'. The secondary mirror has been refigured, together with a change of the exit window (now an exit lens with optical power and positive chromatic effects). The main resulting characteristics are a new f/16.58 F1 (quite close to the former version), and a new position (lower on) for this focus. \\ | ||
| - | < | + | < |
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| + | ==== 1') Polarimetric analyser ==== | ||
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| - | === 2. Full-Sun guider | + | ==== 2) Full-Sun guider |
| - | < | + | < |
| - | | + | |
| - | == Full-sun guider == | + | / |
| - | A full-sun guider has been setup on the telescope outer ring of the heat protection, near the 1m entrance plate. It uses a 45/500 mm objective, an Herschel prism, a neutral filter, a green continuum 540nm photosphere filter, and a ZWO ASI 178 mono (2kx3k) CMOS camera. < | + | |
| + | == Full-sun guider ==*/ | ||
| + | A full-sun guider has been setup on the telescope outer ring of the heat protection, near the 1m entrance plate. It uses a 45/500 mm objective, an Herschel prism, a neutral filter, a green continuum 540nm photosphere filter, and a ZWO ASI 178 mono (2kx3k) CMOS camera. < | ||
| - | This image is always available in the control room. Please note that given the location of the entrance pupil and depending on the telescope/ | + | The full-sun guider |
| /* This is signaled on the guider monitor, and no premature conclusion shall be drawn if this image goes dark during a manual offset of the telescope.*/ | /* This is signaled on the guider monitor, and no premature conclusion shall be drawn if this image goes dark during a manual offset of the telescope.*/ | ||
| \\ | \\ | ||
| - | == nighttime guider == | + | /*== nighttime guider == |
| - | The **historical full-sun guider** still exists, but is now due to become a nighttime guider (sometime). This guider | + | < |
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| + | === 3. F2' instrumentation === | ||
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| + | === 4. Adaptive Optics correction === | ||
| - | **3. F2' instrumentation **\\ | + | See the dedicated page about the [[themis: |
| - | **4. Adaptive Optics correction**\\ | ||
| - | **5. OBJ2 field scanning**\\ | + | === 5. OBJ2 field scanning |
| - | **6. Beam splitters | + | === 6. Beam splitters |
| We currently have no unique solution for a feeding a context camera in all the possible situations of flux. This is why we setup a translation stage with the following beam-splitting options: | We currently have no unique solution for a feeding a context camera in all the possible situations of flux. This is why we setup a translation stage with the following beam-splitting options: | ||
| - | {{ : | ||
| * **Passthrough** (100% transmitted, | * **Passthrough** (100% transmitted, | ||
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| * a 45° mirror slit | * a 45° mirror slit | ||
| - | {{ : | + | |
| The mechanical slit is the " | The mechanical slit is the " | ||
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| Simplified diagram of THEMIS optical path (spectrograph not represented). \\ | Simplified diagram of THEMIS optical path (spectrograph not represented). \\ | ||
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| + | {{: | ||
| /* | /* | ||
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| </ | </ | ||
| - | ---- | ||
| - | < | ||
| - | <font size=" | ||
| - | © 2024 CNRS-THEMIS <br> | ||
| - | Terms of use: unless otherwise specified, all graphical (webcam records, movies, pictures) | ||
| - | </ | ||
