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| themis [2025/11/07 09:58] – etienne | themis [2025/11/07 10:18] (current) – etienne |
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| == THEMIS image of the month: September 2025 == | == THEMIS image of the month: October 2025 == |
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| <html> <a href="https://www.themis.iac.es/lib/exe/fetch.php?media=science:gallery:schema:opticalpath_tao.png | |
| "> <img src="https://www.themis.iac.es/lib/exe/fetch.php?media=science:gallery:schema:opticalpath_tao.png | |
| " alt="Diagram of THEMIS adaptive optic light-path." style="width: 100%; height: auto;"></a></html> \\ | |
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| | <html> <a href="https://www.themis.iac.es/lib/exe/fetch.php?media=science:gallery:instrumentation:themisthroughoculus.jpg |
| | "> <img src="https://www.themis.iac.es/lib/exe/fetch.php?media=science:gallery:instrumentation:themisthroughoculus.jpg |
| | " alt="THEMIS telescope through the dome oculus" style="width: 100%; height: auto;"></a></html> \\ |
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| THEMIS design, laid out in the 1980's, predate the revolution of adaptive optics (AO), and hence didn't foresee its installation. AO has since proved to be an indispensable technology of all modern high-resolution telescope. The core of the THEMIS overhaul that took place in the second half of the 2010's had the installation of a simple AO at the core of its objective. | <newcolumn 60%> |
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| The installation of the [[technical:tao|THEMIS AO]] was thus particularly challenging as it required to deal with the limited existing available space. The entry prism is thus located just inside the spectrograph container, close to its roof, in a location that is not easily accessible. In addition, as shown in the diagram of TAO, it imposed to place the wavefront sensor optical bench (as well as the scanning mirror) outside of the THEMIS spectrograph container, in a vertical layout. | A view of the THEMIS telescope in its resting safe position seen through the oculus of the dome. The THEMIS dome was designed not only to protect the telescope from inclement weather, but also to avoid direct sunlight heating the floor around the telescope mount. Such heat induces turbulence that can significantly impact the quality of the observations. In order for THEMIS to observe, the oculus has precisely the size of the telescope aperture. While observing the only sunlight that gets in the dome goes in the telescope. Both the telescope and the oculus must then move smoothly and synchronously when tracking the Sun during its diurnal motion. |
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