Mirrors | ELT

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Overview</a> <a class="nav-science-solarsystem dropdown-item" href="/web/20210123234724/https://elt.eso.org/science/solarsystem/">Solar System</a> <a class="nav-science-exoplanets dropdown-item" href="/web/20210123234724/https://elt.eso.org/science/exoplanets/">Exoplanets</a> <a class="nav-science-stars dropdown-item" href="/web/20210123234724/https://elt.eso.org/science/stars/">Stars</a> <a class="nav-science-blackholes dropdown-item" href="/web/20210123234724/https://elt.eso.org/science/blackholes/">Black Holes</a> <a class="nav-science-galaxies dropdown-item" href="/web/20210123234724/https://elt.eso.org/science/galaxies/">Galaxies</a> <a class="nav-science-cosmodm dropdown-item" href="/web/20210123234724/https://elt.eso.org/science/cosmodm/">Cosmology and Dark Matter</a> <a class="nav-science-fundamentalphysics dropdown-item" href="/web/20210123234724/https://elt.eso.org/science/fundamentalphysics/">Fundamental Physics</a> <a class="nav-science-discoveries dropdown-item" href="/web/20210123234724/https://elt.eso.org/science/discoveries/">Unexpected Discoveries</a> </div> </li> <li class="nav-multimedia nav-item menu-item d-flex align-items-center text-center"> <a class="nav-link" href="/web/20210123234724/https://elt.eso.org/media/">NEWS & MULTIMEDIA</a> </li> <li class="nav-success nav-item menu-item d-flex align-items-center text-center"> <a class="nav-link" href="/web/20210123234724/https://elt.eso.org/success/buildingon/">SUCCESS STORIES</a> </li>           </ul> </div> </nav> <div class="container-fluid container-light page-section container-y-2"> <div class="container-paragraph section-title-paragraph d-flex align-items-center justify-content-between"> <div class="">The path of light through the ELT</div>                      <div class="d-flex"> <a class="share-social-media-link share-social-media-icons" href="https://web.archive.org/web/20210123234724/https://www.facebook.com/sharer/sharer.php?u=https://elt.eso.org/" title="Share on Facebook" 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href="https://web.archive.org/web/20210123234724/https://www.facebook.com/sharer/sharer.php?u=https://elt.eso.org/" title="Share on Facebook" target="_blank"> <img src="/web/20210123234724im_/https://elt.eso.org/public/archives/djp/elt-assets/img/social-media/icon_share_1.png" alt="Share on Facebook"> <span class="share-social-media-dropdown-text">Share on Facebook</span> </a> <a class="share-social-media-link share-email" href="#" title="E-Mail"> <img src="/web/20210123234724im_/https://elt.eso.org/public/archives/djp/elt-assets/img/social-media/icon_share_5.png" alt="E-Mail"> <span class="share-social-media-dropdown-text">E-Mail</span> </a> <a class="share-social-media-link" href="https://web.archive.org/web/20210123234724/http://twitter.com/intent/tweet?url=https://elt.eso.org/&text=&via=ESO" title="Share on Twitter" target="_blank"> <img src="/web/20210123234724im_/https://elt.eso.org/public/archives/djp/elt-assets/img/social-media/icon_share_2.png" alt"share on twitter"> <span class="share-social-media-dropdown-text">Share on Twitter</span> </a> <a href="#" class="share-social-media-link clipboard" title="Copy Link"> <img src="/web/20210123234724im_/https://elt.eso.org/public/archives/djp/elt-assets/img/social-media/icon_share_6.png" alt="Copy link"> <span class="share-social-media-dropdown-text">Copy Link</span> </a> <a class="share-social-media-link" href="https://web.archive.org/web/20210123234724/https://www.linkedin.com/sharing/share-offsite/?url=https://elt.eso.org/" title="Share on LinkedIn" target="_blank"> <img src="/web/20210123234724im_/https://elt.eso.org/public/archives/djp/elt-assets/img/social-media/icon_share_4.png" alt="Share on LinkedIn"> <span class="share-social-media-dropdown-text">Share on LinkedIn</span> </a> </div> </div> </span> </div> </div> <div class="container-paragraph section-text-paragraph"> <p>The ELT will have a pioneering five-mirror optical design that will allow it to unveil the Universe in unprecedented detail. The mirrors all have different shapes, sizes and roles but will work together seamlessly. The primary, M1, is the most spectacular: a giant 39-metre concave mirror that will collect light from the night sky and reflect it to the secondary mirror. The convex M2, the largest secondary mirror ever employed on a telescope, will hang above M1 and will reflect light back down to M3, which in turn will relay it to an adaptive flat mirror (M4) above it. This fourth mirror will adjust its shape a thousand times a second to correct for distortions caused by atmospheric turbulence, before sending the light to M5, a flat tiltable mirror that will stabilise the image and send it to the ELT instruments.</p> <p>The optical solution for the ESO ELT is a 39-m aperture folded three-mirror anastigmat (M1,鈥疢2, M3). Folding is provided by two flat mirrors (M4,鈥疢5) sending the beams to either Nasmyth foci (prefocal stations) along the elevation axis of the telescope.</p> </div> <div class="w-100 d-flex pb-5 mx-auto container-paragraph"> <div class="embed-responsive embed-responsive-16by9"> <iframe class="embed-responsive-item" src="https://web.archive.org/web/20210123234724if_/https://www.youtube.com/embed/aqfLGrpOjjY" style="width: 100%" allowfullscreen></iframe> </div> </div> <div class="container-paragraph section-text-paragraph"> <p>The focal ratio of the primary mirror (<a href="/web/20210123234724/https://elt.eso.org/mirror/M1/">M1</a>) is f/0.87. The total Nasmyth field of view is 10 arc minutes, limited by the dimensions of the way-through hole in one of the flat folding mirrors (<a href="/web/20210123234724/https://elt.eso.org/mirror/M4/">M4</a>). As-designed optical quality is diffraction limited up to the edge of the curved field at all wavelengths. Field curvature is 9 88 m and the centre of field curvature is before the focus. The Nasmyth focal ratio is rather large (f/17.75, focal length 684022 mm). The folding arrangement (flat聽<a href="/web/20210123234724/https://elt.eso.org/mirror/M4/">M4</a>聽and聽<a href="/web/20210123234724/https://elt.eso.org/mirror/M5/">M5</a>聽mirrors) is conceived to provide conveniently located flat surfaces for an adaptive mirror (<a href="/web/20210123234724/https://elt.eso.org/mirror/M4/">M4</a>, conjugated to 621 m in front of the telescope, from聽<a href="/web/20210123234724/https://elt.eso.org/mirror/M1/">M1</a>) and field stabilisation (<a href="/web/20210123234724/https://elt.eso.org/mirror/M5/">M5</a>, with a minor off-pupil effect). The聽<a href="/web/20210123234724/https://elt.eso.org/mirror/M4/">M4</a>聽mirror is inclined by 7.75掳.</p> <p>The telescope is highly dependent on integrated wavefront control, the purpose of which is to maintain the wavefront and the tracking within tolerances. This allows for limited drifts of the state and alignment of the optical surfaces, provided that mutual compensations hold the telescope to tolerances.</p> <p>All mirrors bar聽<a href="/web/20210123234724/https://elt.eso.org/mirror/M5/">M5</a>聽have shape adjustment capability to some extent; mirrors聽<a href="/web/20210123234724/https://elt.eso.org/mirror/M2M3/">M2</a>聽and聽<a href="/web/20210123234724/https://elt.eso.org/mirror/M2M3/">M3</a>聽can be recentred, while mirrors聽<a href="/web/20210123234724/https://elt.eso.org/mirror/M4/">M4</a>聽and聽<a href="/web/20210123234724/https://elt.eso.org/mirror/M5/">M5</a>聽can steer the beams to dynamically adjust the line of sight according to surfaces misalignment, jitter and residues from the telescope kinematics.</p> </div> </div> <div class="container-fluid container-dark container-tight position-relative"> <img class="d-block h-100 w-100" src="https://web.archive.org/web/20210123234724im_/https://cdn.eso.org/images/banner1920/header-mirrors-m1.jpg"/> <div class="position-absolute mirror-landing-menu-textblock"> <div class="d-flex flex-column justify-content-around h-100"> <a class="position-absolute_ w-100_ mirror-landing-menu-title" href="/web/20210123234724/https://elt.eso.org/mirror/M1/">M1 Mirror</a> <div class="position-absolute_ w-100_ d-none d-md-block mirror-landing-menu-subtitle"><p>The giant primary mirror</p></div> <div class="position-absolute_ w-100_ d-none d-xl-block mirror-landing-menu-description"> <p>The 39-metre-diameter primary mirror, which will be made up of 798 individual hexagonal segments each measuring 1.4 metres across, will be by far the largest ever made for an optical telescope. Together, the segments will collect tens of millions of times as much light as the human eye.</p> </div> </div> </div> <div class="position-absolute d-flex align-items-start triangle-down"> <div id="triangle-down"></div> </div> <div class="w-100 position-absolute d-flex align-items-end" style="bottom: 0%; left: 0%"> <div class="w-100 d-block"> <svg class="instrument-landing-trapezoid" viewbox="0 -1 1890 128" preserveaspectratio="none" style="/* height: 110px; */"> <a href="/web/20210123234724/https://elt.eso.org/mirror/M1/"> <polygon class="landing-polygon" points="0,0 630,0 819,110 1890,110 1890,126 0,126"/> <polyline class="landing-polyline" points="0,0 630,0 819,110 1890,110"/> <polyline class="landing-polyline" points="0,126 1890,126"/> </a> </svg> </div> </div> <div class="position-absolute d-flex align-items-center justify-content-center instrument-landing-trapezoid-link"> <a href="/web/20210123234724/https://elt.eso.org/mirror/M1/" class="instrument-landing-trapezoid-link"> Read more </a> </div> </div> <div class="container-fluid container-dark container-tight position-relative"> <img class="d-block h-100 w-100" src="https://web.archive.org/web/20210123234724im_/https://cdn.eso.org/images/banner1920/header-mirrors-m2-m3.jpg"/> <div class="position-absolute mirror-landing-menu-textblock"> <div class="d-flex flex-column justify-content-around h-100"> <a class="position-absolute_ w-100_ mirror-landing-menu-title" href="/web/20210123234724/https://elt.eso.org/mirror/M2M3/">M2 and M3 Mirrors</a> <div class="position-absolute_ w-100_ d-none d-md-block mirror-landing-menu-subtitle"><p>Perfecting image quality</p></div> <div class="position-absolute_ w-100_ d-none d-xl-block mirror-landing-menu-description"> <p>The ELT鈥檚 secondary mirror is the largest convex mirror ever produced. It will reflect light collected by M1 to the tertiary mirror M3, a concave mirror similar in size to M2. The three curved mirrors will allow the ELT to deliver a better image quality over a larger field of view than what would be possible otherwise.</p> </div> </div> </div> <div class="w-100 position-absolute d-flex align-items-end" style="bottom: 0%; left: 0%"> <div class="w-100 d-block"> <svg class="instrument-landing-trapezoid" viewbox="0 -1 1890 128" preserveaspectratio="none" style="/* height: 110px; */"> <a href="/web/20210123234724/https://elt.eso.org/mirror/M2M3/"> <polygon class="landing-polygon" points="0,0 630,0 819,110 1890,110 1890,126 0,126"/> <polyline class="landing-polyline" points="0,0 630,0 819,110 1890,110"/> <polyline class="landing-polyline" points="0,126 1890,126"/> </a> </svg> </div> </div> <div class="position-absolute d-flex align-items-center justify-content-center instrument-landing-trapezoid-link"> <a href="/web/20210123234724/https://elt.eso.org/mirror/M2M3/" class="instrument-landing-trapezoid-link"> Read more </a> </div> </div> <div class="container-fluid container-dark container-tight position-relative"> <img class="d-block h-100 w-100" src="https://web.archive.org/web/20210123234724im_/https://cdn.eso.org/images/banner1920/header-mirrors-m4.jpg"/> <div class="position-absolute mirror-landing-menu-textblock"> <div class="d-flex flex-column justify-content-around h-100"> <a class="position-absolute_ w-100_ mirror-landing-menu-title" href="/web/20210123234724/https://elt.eso.org/mirror/M4/">M4 Mirror</a> <div class="position-absolute_ w-100_ d-none d-md-block mirror-landing-menu-subtitle"><p>The largest adaptive mirror ever built</p></div> <div class="position-absolute_ w-100_ d-none d-xl-block mirror-landing-menu-description"> <p>A true technological wonder, the ELT鈥檚 fourth mirror is the largest deformable mirror ever made. Its surface can be distorted and adapted to correct for atmospheric turbulence and the residual vibration of the telescope itself, allowing for the delivery of sharp images needed for science.</p> </div> </div> </div> <div class="w-100 position-absolute d-flex align-items-end" style="bottom: 0%; left: 0%"> <div class="w-100 d-block"> <svg class="instrument-landing-trapezoid" viewbox="0 -1 1890 128" preserveaspectratio="none" style="/* height: 110px; */"> <a href="/web/20210123234724/https://elt.eso.org/mirror/M4/"> <polygon class="landing-polygon" points="0,0 630,0 819,110 1890,110 1890,126 0,126"/> <polyline class="landing-polyline" points="0,0 630,0 819,110 1890,110"/> <polyline class="landing-polyline" points="0,126 1890,126"/> </a> </svg> </div> </div> <div class="position-absolute d-flex align-items-center justify-content-center instrument-landing-trapezoid-link"> <a href="/web/20210123234724/https://elt.eso.org/mirror/M4/" class="instrument-landing-trapezoid-link"> Read more </a> </div> </div> <div class="container-fluid container-dark container-tight position-relative"> <img class="d-block h-100 w-100" src="https://web.archive.org/web/20210123234724im_/https://cdn.eso.org/images/banner1920/header-mirrors-m5.jpg"/> <div class="position-absolute mirror-landing-menu-textblock"> <div class="d-flex flex-column justify-content-around h-100"> <a class="position-absolute_ w-100_ mirror-landing-menu-title" href="/web/20210123234724/https://elt.eso.org/mirror/M5/">M5 Mirror</a> <div class="position-absolute_ w-100_ d-none d-md-block mirror-landing-menu-subtitle"><p>The largest tip-tilt mirror in the world</p></div> <div class="position-absolute_ w-100_ d-none d-xl-block mirror-landing-menu-description"> <p>M5 is the smallest mirror on the ELT, but the biggest tip-tilt mirror ever employed in a telescope. Together with M4, it is a crucial component of the ELT鈥檚 adaptive optics system. Its precise tip and tilt movements will鈥痚nsure images are stabilised before they reach the ELT instruments.</p> </div> </div> </div> <div class="w-100 position-absolute d-flex align-items-end" style="bottom: 0%; left: 0%"> <div class="w-100 d-block"> <svg class="instrument-landing-trapezoid" viewbox="0 -1 1890 128" preserveaspectratio="none" style="/* height: 110px; */"> <a href="/web/20210123234724/https://elt.eso.org/mirror/M5/"> <polygon class="landing-polygon" points="0,0 630,0 819,110 1890,110 1890,126 0,126"/> <polyline class="landing-polyline" points="0,0 630,0 819,110 1890,110"/> <polyline class="landing-polyline" points="0,126 1890,126"/> </a> </svg> </div> </div> <div class="position-absolute d-flex align-items-center justify-content-center instrument-landing-trapezoid-link"> <a href="/web/20210123234724/https://elt.eso.org/mirror/M5/" class="instrument-landing-trapezoid-link"> Read more </a> </div> </div> <footer class="container-fluid container-footer"> <div class="row d-flex align-items-center justify-content-between w-100"> <div class="col-12 col-lg-3 pb-3 pb-lg-0 d-flex align-items-center justify-content-center medium-light footer-item"> <a href="https://web.archive.org/web/20210123234724/https://elt.eso.org/www.eso.org/"><span class="esoblue">ESO</span></a> | ELT © 2020 </div> <div class="col-12 col-lg-9 d-flex align-items-center justify-content-center medium-light footer-item"> <div class="text-center"> <a class="w-100" href="/web/20210123234724/https://elt.eso.org/credits/"><span class="medium-light footer-item">Credits</span></a>   |   <a class="w-100" href="https://web.archive.org/web/20210123234724/mailto:information@eso.org"><span class="medium-light footer-item">Contact us</span></a>   |   <a class="w-100" href="https://web.archive.org/web/20210123234724/https://www.eso.org/public/outreach/newsletters/"><span class="medium-light footer-item">Subscribe to ESO news</span></a>   |   <a class="w-100" href="https://web.archive.org/web/20210123234724/https://www.cdn77.com/"><span class="medium-light footer-item">Accelerated by CDN77</span></a>   |   <a class="w-100" href="https://web.archive.org/web/20210123234724/https://www.eso.org/public/about-eso/privacy/"><span class="medium-light footer-item">Terms & Conditions</span></a> </div> </div> </div> </footer> <input type="hidden" name="csrfmiddlewaretoken" value="4xdxLQiXQBkGgSgmGGxFWfjMx7t8HNB7RHkpcO6EPlTjeAoufovUzJ8LLgGdHk6p"/> </body> </html>

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