Glossary term: आरसा
Description: आरसा हे एक ऑप्टिकल उपकरण आहे जे त्याच्या पृष्ठभागावरून प्रकाश प्रतिबिंबित करते. बहिर्वक्र आरसे प्रकाशाचे किरण पसरवतात आणि अवतल आरसे प्रकाश किरणांना केंद्रित करतात. प्रकाशाच्या समांतर किरणांना एका बिंदूवर केंद्रित करण्यासाठी अवतल आरशांना आकार दिला जाऊ शकतो. बहुतेक आधुनिक दुर्बिणी त्यांचे प्राथमिक संकलन क्षेत्र म्हणून मोठे अवतल आरसे वापरतात.
खगोलशास्त्रीय दुर्बिणींमध्ये वापरल्या जाणार्या बहुतेक आरशांचा मुख्य भाग काचेचा असतो. आरशासाठी कधीकधी वापरल्या जाणार्या काचेमध्ये इतर सामग्री, जसे सिरॅमिक्स आणि धातूं यांचा वापर होतो. आरश्याच्या काचेला घासून आकार दिला जातो आणि त्यानंतर पॉलिश केले जाते आणि जर काच आधीच परावर्तित नसेल तर पृष्ठभागावर पातळ धातूचा लेप लावला जातो. साधारणपणे ॲल्युमिनियम हा पदार्थ लेप लावण्यासाठी वापरला जातो, परंतु सोने किंवा चांदी हे देखील पर्याय आहेत.
सुमारे 6 मीटर व्यासापेक्षा मोठ्या दुर्बिणीसाठी, अशा विशाल काचेच्या आरशांना कास्ट करणे आणि समर्थन देणे कठीण आहे. परिणामी, जगातील काही सर्वात मोठ्या दुर्बिणी आता अनेक लहान आरशांचा वापर करतात जेथे एक महाकाय आरसा असल्यासारखे प्रकाश केंद्रित करण्यासाठी त्या लहान आरशांची व्यवस्थित रचना केलेली असते.
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Term and definition status: The original definition of this term in English have been approved by a research astronomer and a teacher The translation of this term and its definition is still awaiting approval
The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".
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Gemini South's primary mirror and telescope structure
Caption: This is the primary mirror and supporting structure of a large optical telescope at the Gemini South Observatory in Chile. The primary mirror is the largest and most important mirror in a reflecting telescope: its gently curved surface gathers light from faint stars, galaxies, and nebulae and reflects that light to a focal point. At this focal point light is either fed directly in to an instrument to record spectra and images or redirected to such an instrument by a series of further mirrors. The sturdy metal framework around the primary mirros keeps the mirror precisely aligned and protected while the telescope moves to track objects across the sky.
In telescopes that use mirrors instead of lenses, such as this one, the mirror is what collects and focuses the light from distant celestial objects. Larger mirrors can capture more light, allowing astronomers to see fainter and more distant objects. A larger primary mirror can also take sharper images of the sky, but this is often negated by the blurring effect of the Earth's atmopshere. A primary mirror must be perfectly smooth to tolerances of fractions of a wavelength of light so that it produces sharp, clear images. We can think of the primary mirror as the “eye” of the telescope that looks out into space, with its shape and support enabling powerful astronomical observations.
Credit: International Gemini Observatory/NOIRLab/NSF/AURA/M. Paredes
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