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class="vector-toc-numb">2</span> <span>Refracting telescope designs</span> </div> </a> <button aria-controls="toc-Refracting_telescope_designs-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Refracting telescope designs subsection</span> </button> <ul id="toc-Refracting_telescope_designs-sublist" class="vector-toc-list"> <li id="toc-Galilean_telescope" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Galilean_telescope"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.1</span> <span>Galilean telescope</span> </div> </a> <ul id="toc-Galilean_telescope-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Keplerian_telescope" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Keplerian_telescope"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.2</span> <span>Keplerian telescope</span> </div> </a> <ul id="toc-Keplerian_telescope-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Achromatic_refractors" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Achromatic_refractors"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.3</span> <span>Achromatic refractors</span> </div> </a> <ul id="toc-Achromatic_refractors-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Apochromatic_refractors" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Apochromatic_refractors"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.4</span> <span>Apochromatic refractors</span> </div> </a> <ul id="toc-Apochromatic_refractors-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Technical_considerations" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Technical_considerations"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Technical considerations</span> </div> </a> <ul id="toc-Technical_considerations-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Applications_and_achievements" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Applications_and_achievements"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Applications and achievements</span> </div> </a> <ul id="toc-Applications_and_achievements-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-List_of_the_largest_refracting_telescopes" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#List_of_the_largest_refracting_telescopes"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>List of the largest refracting telescopes</span> </div> </a> <ul id="toc-List_of_the_largest_refracting_telescopes-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">7</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">8</span> <span>External links</span> </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" title="Table of Contents" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Toggle the table of contents</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Refracting telescope</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. Available in 53 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-53" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">53 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-als mw-list-item"><a href="https://als.wikipedia.org/wiki/Fernrohr" title="Fernrohr – Alemannic" lang="gsw" hreflang="gsw" data-title="Fernrohr" data-language-autonym="Alemannisch" data-language-local-name="Alemannic" class="interlanguage-link-target"><span>Alemannisch</span></a></li><li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D9%85%D9%82%D8%B1%D8%A7%D8%A8_%D9%83%D8%A7%D8%B3%D8%B1" title="مقراب كاسر – Arabic" lang="ar" hreflang="ar" data-title="مقراب كاسر" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-ast mw-list-item"><a href="https://ast.wikipedia.org/wiki/Telescopiu_refractor" title="Telescopiu refractor – Asturian" lang="ast" hreflang="ast" data-title="Telescopiu refractor" data-language-autonym="Asturianu" data-language-local-name="Asturian" class="interlanguage-link-target"><span>Asturianu</span></a></li><li class="interlanguage-link interwiki-bn mw-list-item"><a href="https://bn.wikipedia.org/wiki/%E0%A6%AA%E0%A7%8D%E0%A6%B0%E0%A6%A4%E0%A6%BF%E0%A6%B8%E0%A6%B0%E0%A6%A3_%E0%A6%A6%E0%A7%82%E0%A6%B0%E0%A6%AC%E0%A6%BF%E0%A6%A8" title="প্রতিসরণ দূরবিন – Bangla" lang="bn" hreflang="bn" data-title="প্রতিসরণ দূরবিন" data-language-autonym="বাংলা" data-language-local-name="Bangla" class="interlanguage-link-target"><span>বাংলা</span></a></li><li class="interlanguage-link interwiki-be mw-list-item"><a href="https://be.wikipedia.org/wiki/%D0%A0%D1%8D%D1%84%D1%80%D0%B0%D0%BA%D1%82%D0%B0%D1%80" title="Рэфрактар – Belarusian" lang="be" hreflang="be" data-title="Рэфрактар" data-language-autonym="Беларуская" data-language-local-name="Belarusian" class="interlanguage-link-target"><span>Беларуская</span></a></li><li class="interlanguage-link interwiki-bg mw-list-item"><a href="https://bg.wikipedia.org/wiki/%D0%A0%D0%B5%D1%84%D1%80%D0%B0%D0%BA%D1%82%D0%BE%D1%80%D0%B5%D0%BD_%D1%82%D0%B5%D0%BB%D0%B5%D1%81%D0%BA%D0%BE%D0%BF" title="Рефракторен телескоп – Bulgarian" lang="bg" hreflang="bg" data-title="Рефракторен телескоп" data-language-autonym="Български" data-language-local-name="Bulgarian" class="interlanguage-link-target"><span>Български</span></a></li><li class="interlanguage-link interwiki-bar mw-list-item"><a href="https://bar.wikipedia.org/wiki/Zuaweziaga" title="Zuaweziaga – Bavarian" lang="bar" hreflang="bar" data-title="Zuaweziaga" data-language-autonym="Boarisch" data-language-local-name="Bavarian" class="interlanguage-link-target"><span>Boarisch</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Telescopi_refractor" title="Telescopi refractor – Catalan" lang="ca" hreflang="ca" data-title="Telescopi refractor" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Refraktor" title="Refraktor – Czech" lang="cs" hreflang="cs" data-title="Refraktor" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-da mw-list-item"><a href="https://da.wikipedia.org/wiki/Refraktor" title="Refraktor – Danish" lang="da" hreflang="da" data-title="Refraktor" data-language-autonym="Dansk" data-language-local-name="Danish" class="interlanguage-link-target"><span>Dansk</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Fernrohr" title="Fernrohr – German" lang="de" hreflang="de" data-title="Fernrohr" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-et mw-list-item"><a href="https://et.wikipedia.org/wiki/Refraktor" title="Refraktor – Estonian" lang="et" hreflang="et" data-title="Refraktor" data-language-autonym="Eesti" data-language-local-name="Estonian" class="interlanguage-link-target"><span>Eesti</span></a></li><li class="interlanguage-link interwiki-el mw-list-item"><a href="https://el.wikipedia.org/wiki/%CE%94%CE%B9%CE%BF%CF%80%CF%84%CF%81%CE%B9%CE%BA%CF%8C_%CF%84%CE%B7%CE%BB%CE%B5%CF%83%CE%BA%CF%8C%CF%80%CE%B9%CE%BF" title="Διοπτρικό τηλεσκόπιο – Greek" lang="el" hreflang="el" data-title="Διοπτρικό τηλεσκόπιο" data-language-autonym="Ελληνικά" data-language-local-name="Greek" class="interlanguage-link-target"><span>Ελληνικά</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Telescopio_refractor" title="Telescopio refractor – Spanish" lang="es" hreflang="es" data-title="Telescopio refractor" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-eo mw-list-item"><a href="https://eo.wikipedia.org/wiki/Refraktoro" title="Refraktoro – Esperanto" lang="eo" hreflang="eo" data-title="Refraktoro" data-language-autonym="Esperanto" data-language-local-name="Esperanto" class="interlanguage-link-target"><span>Esperanto</span></a></li><li class="interlanguage-link interwiki-eu mw-list-item"><a href="https://eu.wikipedia.org/wiki/Errefrakzio-teleskopio" title="Errefrakzio-teleskopio – Basque" lang="eu" hreflang="eu" data-title="Errefrakzio-teleskopio" data-language-autonym="Euskara" data-language-local-name="Basque" class="interlanguage-link-target"><span>Euskara</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D8%AA%D9%84%D8%B3%DA%A9%D9%88%D9%BE_%D8%B4%DA%A9%D8%B3%D8%AA%DB%8C" title="تلسکوپ شکستی – Persian" lang="fa" hreflang="fa" data-title="تلسکوپ شکستی" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Lunette_astronomique" title="Lunette astronomique – French" lang="fr" hreflang="fr" data-title="Lunette astronomique" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-gl mw-list-item"><a href="https://gl.wikipedia.org/wiki/Telescopio_refractor" title="Telescopio refractor – Galician" lang="gl" hreflang="gl" data-title="Telescopio refractor" data-language-autonym="Galego" data-language-local-name="Galician" class="interlanguage-link-target"><span>Galego</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%EA%B5%B4%EC%A0%88_%EB%A7%9D%EC%9B%90%EA%B2%BD" title="굴절 망원경 – Korean" lang="ko" hreflang="ko" data-title="굴절 망원경" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-hy mw-list-item"><a href="https://hy.wikipedia.org/wiki/%D5%8C%D5%A5%D6%86%D6%80%D5%A1%D5%AF%D5%BF%D5%B8%D6%80" title="Ռեֆրակտոր – Armenian" lang="hy" hreflang="hy" data-title="Ռեֆրակտոր" data-language-autonym="Հայերեն" data-language-local-name="Armenian" class="interlanguage-link-target"><span>Հայերեն</span></a></li><li class="interlanguage-link interwiki-hi mw-list-item"><a href="https://hi.wikipedia.org/wiki/%E0%A4%85%E0%A4%AA%E0%A4%B5%E0%A4%B0%E0%A5%8D%E0%A4%A4%E0%A5%80_%E0%A4%A6%E0%A5%82%E0%A4%B0%E0%A4%A6%E0%A4%B0%E0%A5%8D%E0%A4%B6%E0%A5%80" title="अपवर्ती दूरदर्शी – Hindi" lang="hi" hreflang="hi" data-title="अपवर्ती दूरदर्शी" data-language-autonym="हिन्दी" data-language-local-name="Hindi" class="interlanguage-link-target"><span>हिन्दी</span></a></li><li class="interlanguage-link interwiki-hr mw-list-item"><a href="https://hr.wikipedia.org/wiki/Refraktorski_teleskop" title="Refraktorski teleskop – Croatian" lang="hr" hreflang="hr" data-title="Refraktorski teleskop" data-language-autonym="Hrvatski" data-language-local-name="Croatian" class="interlanguage-link-target"><span>Hrvatski</span></a></li><li class="interlanguage-link interwiki-io mw-list-item"><a href="https://io.wikipedia.org/wiki/Refraktoro" title="Refraktoro – Ido" lang="io" hreflang="io" data-title="Refraktoro" data-language-autonym="Ido" data-language-local-name="Ido" class="interlanguage-link-target"><span>Ido</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Telescopio_rifrattore" title="Telescopio rifrattore – Italian" lang="it" hreflang="it" data-title="Telescopio rifrattore" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-he mw-list-item"><a href="https://he.wikipedia.org/wiki/%D7%98%D7%9C%D7%A1%D7%A7%D7%95%D7%A4_%D7%A9%D7%95%D7%91%D7%A8-%D7%90%D7%95%D7%A8" title="טלסקופ שובר-אור – Hebrew" lang="he" hreflang="he" data-title="טלסקופ שובר-אור" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-ht mw-list-item"><a href="https://ht.wikipedia.org/wiki/Telesk%C3%B2p_refrakt%C3%A8" title="Teleskòp refraktè – Haitian Creole" lang="ht" hreflang="ht" data-title="Teleskòp refraktè" data-language-autonym="Kreyòl ayisyen" data-language-local-name="Haitian Creole" class="interlanguage-link-target"><span>Kreyòl ayisyen</span></a></li><li class="interlanguage-link interwiki-lv mw-list-item"><a href="https://lv.wikipedia.org/wiki/Refraktors" title="Refraktors – Latvian" lang="lv" hreflang="lv" data-title="Refraktors" data-language-autonym="Latviešu" data-language-local-name="Latvian" class="interlanguage-link-target"><span>Latviešu</span></a></li><li class="interlanguage-link interwiki-lb mw-list-item"><a href="https://lb.wikipedia.org/wiki/L%C3%ABnserefrakter" title="Lënserefrakter – Luxembourgish" lang="lb" hreflang="lb" data-title="Lënserefrakter" data-language-autonym="Lëtzebuergesch" data-language-local-name="Luxembourgish" class="interlanguage-link-target"><span>Lëtzebuergesch</span></a></li><li class="interlanguage-link interwiki-mk mw-list-item"><a href="https://mk.wikipedia.org/wiki/%D0%A0%D0%B5%D1%84%D1%80%D0%B0%D0%BA%D1%82%D0%BE%D1%80" title="Рефрактор – Macedonian" lang="mk" hreflang="mk" data-title="Рефрактор" data-language-autonym="Македонски" data-language-local-name="Macedonian" class="interlanguage-link-target"><span>Македонски</span></a></li><li class="interlanguage-link interwiki-ml mw-list-item"><a href="https://ml.wikipedia.org/wiki/%E0%B4%85%E0%B4%AA%E0%B4%B5%E0%B5%BC%E0%B4%A4%E0%B5%8D%E0%B4%A4%E0%B4%A8_%E0%B4%A6%E0%B5%82%E0%B4%B0%E0%B4%A6%E0%B5%BC%E0%B4%B6%E0%B4%BF%E0%B4%A8%E0%B4%BF" title="അപവർത്തന ദൂരദർശിനി – Malayalam" lang="ml" hreflang="ml" data-title="അപവർത്തന ദൂരദർശിനി" data-language-autonym="മലയാളം" data-language-local-name="Malayalam" class="interlanguage-link-target"><span>മലയാളം</span></a></li><li class="interlanguage-link interwiki-xmf mw-list-item"><a href="https://xmf.wikipedia.org/wiki/%E1%83%A0%E1%83%94%E1%83%A4%E1%83%A0%E1%83%90%E1%83%A5%E1%83%A2%E1%83%9D%E1%83%A0%E1%83%98" title="რეფრაქტორი – Mingrelian" lang="xmf" hreflang="xmf" data-title="რეფრაქტორი" data-language-autonym="მარგალური" data-language-local-name="Mingrelian" class="interlanguage-link-target"><span>მარგალური</span></a></li><li class="interlanguage-link interwiki-ms mw-list-item"><a href="https://ms.wikipedia.org/wiki/Teleskop_pembiasan" title="Teleskop pembiasan – Malay" lang="ms" hreflang="ms" data-title="Teleskop pembiasan" data-language-autonym="Bahasa Melayu" data-language-local-name="Malay" class="interlanguage-link-target"><span>Bahasa Melayu</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Refractor_(telescoop)" title="Refractor (telescoop) – Dutch" lang="nl" hreflang="nl" data-title="Refractor (telescoop)" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target"><span>Nederlands</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/%E5%B1%88%E6%8A%98%E6%9C%9B%E9%81%A0%E9%8F%A1" title="屈折望遠鏡 – Japanese" lang="ja" hreflang="ja" data-title="屈折望遠鏡" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-no mw-list-item"><a href="https://no.wikipedia.org/wiki/Refraktor" title="Refraktor – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Refraktor" data-language-autonym="Norsk bokmål" data-language-local-name="Norwegian Bokmål" class="interlanguage-link-target"><span>Norsk bokmål</span></a></li><li class="interlanguage-link interwiki-nn mw-list-item"><a href="https://nn.wikipedia.org/wiki/Refraktor" title="Refraktor – Norwegian Nynorsk" lang="nn" hreflang="nn" data-title="Refraktor" data-language-autonym="Norsk nynorsk" data-language-local-name="Norwegian Nynorsk" class="interlanguage-link-target"><span>Norsk nynorsk</span></a></li><li class="interlanguage-link interwiki-oc mw-list-item"><a href="https://oc.wikipedia.org/wiki/Luneta_astronomica" title="Luneta astronomica – Occitan" lang="oc" hreflang="oc" data-title="Luneta astronomica" data-language-autonym="Occitan" data-language-local-name="Occitan" class="interlanguage-link-target"><span>Occitan</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/Telesc%C3%B3pio_refractor" title="Telescópio refractor – Portuguese" lang="pt" hreflang="pt" data-title="Telescópio refractor" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-ro mw-list-item"><a href="https://ro.wikipedia.org/wiki/Lunet%C4%83_astronomic%C4%83" title="Lunetă astronomică – Romanian" lang="ro" hreflang="ro" data-title="Lunetă astronomică" data-language-autonym="Română" data-language-local-name="Romanian" class="interlanguage-link-target"><span>Română</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/%D0%A0%D0%B5%D1%84%D1%80%D0%B0%D0%BA%D1%82%D0%BE%D1%80" title="Рефрактор – Russian" lang="ru" hreflang="ru" data-title="Рефрактор" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-sk mw-list-item"><a href="https://sk.wikipedia.org/wiki/Refraktor" title="Refraktor – Slovak" lang="sk" hreflang="sk" data-title="Refraktor" data-language-autonym="Slovenčina" data-language-local-name="Slovak" class="interlanguage-link-target"><span>Slovenčina</span></a></li><li class="interlanguage-link interwiki-sl mw-list-item"><a href="https://sl.wikipedia.org/wiki/Refraktor" title="Refraktor – Slovenian" lang="sl" hreflang="sl" 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data-event-name="pinnable-header.vector-appearance.unpin">hide</button> </div> </div> </div> </nav> </div> </div> <div id="bodyContent" class="vector-body" aria-labelledby="firstHeading" data-mw-ve-target-container> <div class="vector-body-before-content"> <div class="mw-indicators"> </div> <div id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Type of optical telescope</div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">"Keplerian telescope" redirects here. Not to be confused with <a href="/wiki/Kepler_space_telescope" title="Kepler space telescope">Kepler space telescope</a>.</div> <p class="mw-empty-elt"> </p> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Zeiss2.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/71/Zeiss2.jpg/220px-Zeiss2.jpg" decoding="async" width="220" height="326" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/71/Zeiss2.jpg/330px-Zeiss2.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/71/Zeiss2.jpg/440px-Zeiss2.jpg 2x" data-file-width="479" data-file-height="709" /></a><figcaption>A 200 mm diameter refracting telescope at the <a href="/wiki/Pozna%C5%84_Observatory" title="Poznań Observatory">Poznań Observatory</a></figcaption></figure> <p>A <b>refracting telescope</b> (also called a <b>refractor</b>) is a type of <a href="/wiki/Optical_telescope" title="Optical telescope">optical telescope</a> that uses a <a href="/wiki/Lens_(optics)" class="mw-redirect" title="Lens (optics)">lens</a> as its <a href="/wiki/Objective_(optics)" title="Objective (optics)">objective</a> to form an image (also referred to a <b><a href="/wiki/Dioptrics" title="Dioptrics">dioptric</a> <a href="/wiki/Telescope" title="Telescope">telescope</a></b>). The refracting telescope design was originally used in spyglasses and <a href="/wiki/Astronomy" title="Astronomy">astronomical</a> telescopes but is also used for <a href="/wiki/Long-focus_lens" title="Long-focus lens">long-focus</a> <a href="/wiki/Camera_lens" title="Camera lens">camera lenses</a>. Although large refracting telescopes were very popular in the second half of the 19th century, for most research purposes, the refracting telescope has been superseded by the <a href="/wiki/Reflecting_telescope" title="Reflecting telescope">reflecting telescope</a>, which allows larger <a href="/wiki/Aperture" title="Aperture">apertures</a>. A refractor's <a href="/wiki/Magnification" title="Magnification">magnification</a> is calculated by dividing the focal length of the objective lens by that of the <a href="/wiki/Eyepiece" title="Eyepiece">eyepiece</a>.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> </p><p>Refracting telescopes typically have a lens at the front, then a <a href="/wiki/Optical_train" title="Optical train">long tube</a>, then an eyepiece or instrumentation at the rear, where the telescope view comes to focus. Originally, telescopes had an objective of one element, but a century later, two and even three element lenses were made. </p><p>Refracting telescopes use technology that has often been applied to other optical devices, such as <a href="/wiki/Binoculars" title="Binoculars">binoculars</a> and <a href="/wiki/Zoom_lens" title="Zoom lens">zoom lenses</a>/<a href="/wiki/Telephoto_lens" title="Telephoto lens">telephoto lens</a>/<a href="/wiki/Long-focus_lens" title="Long-focus lens">long-focus lens</a>. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Invention">Invention</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Refracting_telescope&action=edit&section=1" title="Edit section: Invention"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/History_of_the_telescope" title="History of the telescope">History of the telescope</a></div> <p>Refractors were the earliest type of <a href="/wiki/Optical_telescope" title="Optical telescope">optical telescope</a>. The first record of a refracting telescope appeared in the <a href="/wiki/Netherlands" title="Netherlands">Netherlands</a> about 1608, when a spectacle maker from <a href="/wiki/Middelburg,_Zeeland" title="Middelburg, Zeeland">Middelburg</a> named <a href="/wiki/Hans_Lippershey" class="mw-redirect" title="Hans Lippershey">Hans Lippershey</a> unsuccessfully tried to patent one.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> News of the patent spread fast and <a href="/wiki/Galileo_Galilei" title="Galileo Galilei">Galileo Galilei</a>, happening to be in <a href="/wiki/Venice" title="Venice">Venice</a> in the month of May 1609, heard of the invention, constructed <a href="/wiki/Galilean_telescope" class="mw-redirect" title="Galilean telescope">a version of his own</a>, and applied it to making astronomical discoveries.<sup id="cite_ref-:0_3-0" class="reference"><a href="#cite_note-:0-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Refracting_telescope_designs">Refracting telescope designs</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Refracting_telescope&action=edit&section=2" title="Edit section: Refracting telescope designs"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Kepschem.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/2/26/Kepschem.png/400px-Kepschem.png" decoding="async" width="400" height="180" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/2/26/Kepschem.png/600px-Kepschem.png 1.5x, //upload.wikimedia.org/wikipedia/commons/2/26/Kepschem.png 2x" data-file-width="708" data-file-height="319" /></a><figcaption></figcaption></figure> <p>All refracting telescopes use the same principles. The combination of an <a href="/wiki/Objective_(optics)" title="Objective (optics)">objective</a> <a href="/wiki/Lens_(optics)" class="mw-redirect" title="Lens (optics)">lens</a> <b>1</b> and some type of <a href="/wiki/Eyepiece" title="Eyepiece">eyepiece</a> <b>2</b> is used to gather more light than the human eye is able to collect on its own, focus it <b>5</b>, and present the viewer with a <a href="/wiki/Brightness" title="Brightness">brighter</a>, <a href="https://en.wiktionary.org/wiki/clarity" class="extiw" title="wikt:clarity">clearer</a>, and <a href="/wiki/Magnification" title="Magnification">magnified</a> <a href="/wiki/Virtual_image" title="Virtual image">virtual image</a> <b>6</b>. </p><p>The objective in a refracting telescope <a href="/wiki/Refraction" title="Refraction">refracts</a> or bends <a href="/wiki/Light" title="Light">light</a>. This refraction causes <a href="/wiki/Parallel_(geometry)" title="Parallel (geometry)">parallel</a> light rays to converge at a <a href="/wiki/Focus_(optics)" title="Focus (optics)">focal point</a>; while those not parallel converge upon a <a href="/wiki/Focal_plane" class="mw-redirect" title="Focal plane">focal plane</a>. The telescope converts a bundle of parallel rays to make an angle α, with the optical axis to a second parallel bundle with angle β. The ratio β/α is called the angular magnification. It equals the ratio between the retinal image sizes obtained with and without the telescope.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p><p>Refracting telescopes can come in many different configurations to correct for image orientation and types of aberration. Because the image was formed by the bending of light, or refraction, these telescopes are called <i>refracting telescopes</i> or <i>refractors</i>. </p> <div class="mw-heading mw-heading3"><h3 id="Galilean_telescope">Galilean telescope</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Refracting_telescope&action=edit&section=3" title="Edit section: Galilean telescope"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1034237262">.mw-parser-output .stack{box-sizing:border-box}.mw-parser-output .stack>div{margin:1px;overflow:hidden}@media all and (min-width:720px){.mw-parser-output .stack-clear-left{float:left;clear:left}.mw-parser-output .stack-clear-right{float:right;clear:right}.mw-parser-output .stack-left{float:left}.mw-parser-output .stack-right{float:right}.mw-parser-output .stack-margin-clear-left{float:left;clear:left;margin-right:1em}.mw-parser-output .stack-margin-clear-right{float:right;clear:right;margin-left:1em}.mw-parser-output .stack-margin-left{float:left;margin-right:1em}.mw-parser-output .stack-margin-right{float:right;margin-left:1em}}</style><div class="stack mw-stack stack-right"><div><figure typeof="mw:File/Thumb"><a href="/wiki/File:Galileantelescope.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/4/4c/Galileantelescope.png/400px-Galileantelescope.png" decoding="async" width="400" height="141" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/4c/Galileantelescope.png/600px-Galileantelescope.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/4c/Galileantelescope.png/800px-Galileantelescope.png 2x" data-file-width="924" data-file-height="326" /></a><figcaption> <b>Optical diagram of Galilean telescope</b> <b>y</b> – Distant object; <b>y′</b> – Real image from objective; <b> y″</b> – Magnified virtual image from eyepiece; <b>D</b> – Entrance pupil diameter; <b>d</b> – Virtual exit pupil diameter; <b> L1</b> – Objective lens; <b> L2</b> – Eyepiece lens <b>e</b> – Virtual exit pupil – <b>Telescope equals</b> </figcaption></figure></div></div> <p>The design <a href="/wiki/Galileo_Galilei" title="Galileo Galilei">Galileo Galilei</a> used <abbr title="circa">c.</abbr><span style="white-space:nowrap;"> 1609</span> is commonly called a <b>Galilean telescope</b>.<sup id="cite_ref-:3_5-0" class="reference"><a href="#cite_note-:3-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> It used a convergent (plano-convex) objective lens and a divergent (plano-concave) eyepiece lens (Galileo, 1610).<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> A Galilean telescope, because the design has no intermediary focus, results in a non-inverted (i.e., upright) image.<sup id="cite_ref-:6_7-0" class="reference"><a href="#cite_note-:6-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </p><p>Galileo's most powerful telescope, with a total length of just under 1 meter (39 in),<sup id="cite_ref-:3_5-1" class="reference"><a href="#cite_note-:3-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Magnification" title="Magnification">magnified</a> objects about 30 times.<sup id="cite_ref-:6_7-1" class="reference"><a href="#cite_note-:6-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> Galileo had to work with the poor lens technology of the time, and found he had to use aperture stops to reduce the diameter of the objective lens (increase its <a href="/wiki/Focal_ratio" class="mw-redirect" title="Focal ratio">focal ratio</a>) to limit aberrations, so his telescope produced blurry and distorted images with a narrow field of view.<sup id="cite_ref-:6_7-2" class="reference"><a href="#cite_note-:6-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> Despite these flaws, the telescope was still good enough for Galileo to explore the sky. He used it to view <a href="/wiki/Impact_crater" title="Impact crater">craters</a> on the <a href="/wiki/Moon" title="Moon">Moon</a>,<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> the four <a href="/wiki/Galilean_moons" title="Galilean moons">largest moons of Jupiter</a>,<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> and the <a href="/wiki/Phases_of_Venus" title="Phases of Venus">phases of Venus</a>.<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> </p><p>Parallel rays of light from a distant object (<b>y</b>) would be brought to a focus in the focal plane of the objective lens (<b>F′ L1 / y′</b>). The (diverging) eyepiece (<b>L2</b>) lens intercepts these rays and renders them parallel once more. Non-parallel rays of light from the object traveling at an angle <b>α1</b> to the optical axis travel at a larger angle (<b>α2 > α1</b>) after they passed through the eyepiece. This leads to an increase in the apparent angular size and is responsible for the perceived magnification.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (September 2024)">citation needed</span></a></i>]</sup> </p><p>The final image (<b>y″</b>) is a virtual image, located at infinity and is the same way up (i.e., non-inverted or upright) as the object.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (September 2024)">citation needed</span></a></i>]</sup> </p> <div class="mw-heading mw-heading3"><h3 id="Keplerian_telescope">Keplerian telescope</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Refracting_telescope&action=edit&section=4" title="Edit section: Keplerian telescope"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Houghton_Typ_620.73.451_-_Johannes_Hevelius,_Machinae_coelestis,_1673.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/9/9a/Houghton_Typ_620.73.451_-_Johannes_Hevelius%2C_Machinae_coelestis%2C_1673.jpg/220px-Houghton_Typ_620.73.451_-_Johannes_Hevelius%2C_Machinae_coelestis%2C_1673.jpg" decoding="async" width="220" height="184" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/9a/Houghton_Typ_620.73.451_-_Johannes_Hevelius%2C_Machinae_coelestis%2C_1673.jpg/330px-Houghton_Typ_620.73.451_-_Johannes_Hevelius%2C_Machinae_coelestis%2C_1673.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/9a/Houghton_Typ_620.73.451_-_Johannes_Hevelius%2C_Machinae_coelestis%2C_1673.jpg/440px-Houghton_Typ_620.73.451_-_Johannes_Hevelius%2C_Machinae_coelestis%2C_1673.jpg 2x" data-file-width="4635" data-file-height="3879" /></a><figcaption>Engraved illustration of a 46 m (150 ft) focal length Keplerian astronomical refracting telescope built by Johannes Hevelius.<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup></figcaption></figure> <p>The <b>Keplerian telescope</b>, invented by <a href="/wiki/Johannes_Kepler" title="Johannes Kepler">Johannes Kepler</a> in 1611, is an improvement on Galileo's design.<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> It uses a convex lens as the eyepiece instead of Galileo's concave one. The advantage of this arrangement is that the rays of light emerging from the eyepiece<sup class="noprint Inline-Template" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Accuracy_dispute#Disputed_statement" title="Wikipedia:Accuracy dispute"><span title="The material near this tag is possibly inaccurate or nonfactual. (November 2019)">dubious</span></a> – <a href="/wiki/Talk:Refracting_telescope#Dubious" title="Talk:Refracting telescope">discuss</a></i>]</sup> are converging. This allows for a much wider field of view and greater <a href="/wiki/Eye_relief" title="Eye relief">eye relief</a>, but the image for the viewer is inverted. Considerably higher magnifications can be reached with this design, but, like the Galilean telescope, it still uses simple single element objective lens so needs to have a very high focal ratio to reduce aberrations<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> (<a href="/wiki/Johannes_Hevelius" title="Johannes Hevelius">Johannes Hevelius</a> built an unwieldy f/225 telescope with a 200-millimetre (8 in) objective and a 46-metre (150 ft) <a href="/wiki/Focal_length" title="Focal length">focal length</a>,<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup><sup class="noprint Inline-Template" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citing_sources" title="Wikipedia:Citing sources"><span title="This citation requires a reference to the specific page or range of pages in which the material appears. (July 2024)">page needed</span></a></i>]</sup> and even longer tubeless "<a href="/wiki/Aerial_telescope" title="Aerial telescope">aerial telescopes</a>" were constructed). The design also allows for use of a <a href="/wiki/Filar_micrometer#Prior_devices" title="Filar micrometer">micrometer</a> at the focal plane (to determine the angular size and/or distance between objects observed). </p><p><a href="/wiki/Constantijn_Huygens_Jr." title="Constantijn Huygens Jr.">Huygens</a> built an aerial telescope for <a href="/wiki/Royal_Society_of_London" class="mw-redirect" title="Royal Society of London">Royal Society of London</a> with a 19 cm (7.5″) single-element lens.<sup id="cite_ref-stjarnhimlen.se_15-0" class="reference"><a href="#cite_note-stjarnhimlen.se-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Achromatic_refractors">Achromatic refractors</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Refracting_telescope&action=edit&section=5" title="Edit section: Achromatic refractors"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Achromatic_telescope" title="Achromatic telescope">Achromatic telescope</a></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1034237262"><div class="stack mw-stack stack-right"><div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Yerkes_Observatory_Astro4p6.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/87/Yerkes_Observatory_Astro4p6.jpg/220px-Yerkes_Observatory_Astro4p6.jpg" decoding="async" width="220" height="173" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/87/Yerkes_Observatory_Astro4p6.jpg/330px-Yerkes_Observatory_Astro4p6.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/87/Yerkes_Observatory_Astro4p6.jpg/440px-Yerkes_Observatory_Astro4p6.jpg 2x" data-file-width="450" data-file-height="354" /></a><figcaption>Alvan Clark polishes the big Yerkes achromatic objective lens, over 1 meter (100 cm) across (1896).</figcaption></figure> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Irving_Porter_Church_Telescope.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/1/18/Irving_Porter_Church_Telescope.jpg/220px-Irving_Porter_Church_Telescope.jpg" decoding="async" width="220" height="165" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/18/Irving_Porter_Church_Telescope.jpg/330px-Irving_Porter_Church_Telescope.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/1/18/Irving_Porter_Church_Telescope.jpg/440px-Irving_Porter_Church_Telescope.jpg 2x" data-file-width="2048" data-file-height="1536" /></a><figcaption>This 12-inch (30 cm) refractor is mounted in a dome on a mount that matches the Earth's rotation.</figcaption></figure> </div></div> <p>The next major step in the evolution of refracting telescopes was the invention of the <b><a href="/wiki/Achromatic_lens" title="Achromatic lens">achromatic lens</a></b>, a lens with multiple elements that helped solve problems with chromatic aberration and allowed shorter focal lengths. It was invented in 1733 by an English barrister named <a href="/wiki/Chester_Moore_Hall" title="Chester Moore Hall">Chester Moore Hall</a>, although it was independently invented and patented by <a href="/wiki/John_Dollond" title="John Dollond">John Dollond</a> around 1758. The design overcame the need for very long focal lengths in refracting telescopes by using an objective made of two pieces of <a href="/wiki/Glass" title="Glass">glass</a> with different <a href="/wiki/Dispersion_(optics)" title="Dispersion (optics)">dispersion</a>, '<a href="/wiki/Crown_glass_(optics)" title="Crown glass (optics)">crown</a>' and '<a href="/wiki/Flint_glass" title="Flint glass">flint glass</a>', to reduce <a href="/wiki/Chromatic_aberration" title="Chromatic aberration">chromatic</a> and <a href="/wiki/Spherical_aberration" title="Spherical aberration">spherical aberration</a>. Each side of each piece is ground and <a href="/wiki/Polishing" title="Polishing">polished</a>, and then the two pieces are assembled together. Achromatic lenses are corrected to bring two <a href="/wiki/Wavelength" title="Wavelength">wavelengths</a> (typically red and blue) into focus in the same plane.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (September 2024)">citation needed</span></a></i>]</sup> </p><p>Chester More Hall is noted as having made the first twin color corrected lens in 1730.<sup id="cite_ref-16" class="reference"><a href="#cite_note-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> </p><p>Dollond achromats were quite popular in the 18th century.<sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-:4_18-0" class="reference"><a href="#cite_note-:4-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> A major appeal was they could be made shorter.<sup id="cite_ref-:4_18-1" class="reference"><a href="#cite_note-:4-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> However, problems with glass making meant that the glass objectives were not made more than about four inches (10 cm) in diameter.<sup id="cite_ref-:4_18-2" class="reference"><a href="#cite_note-:4-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> </p><p>In the late 19th century, the Swiss optician Pierre-Louis Guinand<sup id="cite_ref-19" class="reference"><a href="#cite_note-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> developed a way to make higher quality glass blanks of greater than four inches (10 cm).<sup id="cite_ref-:4_18-3" class="reference"><a href="#cite_note-:4-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> He passed this technology to his apprentice <a href="/wiki/Joseph_von_Fraunhofer" title="Joseph von Fraunhofer">Joseph von Fraunhofer</a>, who further developed this technology and also developed the Fraunhofer doublet lens design.<sup id="cite_ref-:4_18-4" class="reference"><a href="#cite_note-:4-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> The breakthrough in glass making techniques led to the great refractors of the 19th century, that became progressively larger through the decade, eventually reaching over 1 meter by the end of that century before being superseded by silvered-glass reflecting telescopes in astronomy.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (September 2024)">citation needed</span></a></i>]</sup> </p><p>Noted lens makers of the 19th century include:<sup id="cite_ref-20" class="reference"><a href="#cite_note-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> </p> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1034237262"><div class="stack mw-stack stack-right"><div><figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:The_28-inch_Telescope.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/9/9b/The_28-inch_Telescope.jpg/220px-The_28-inch_Telescope.jpg" decoding="async" width="220" height="431" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/9b/The_28-inch_Telescope.jpg/330px-The_28-inch_Telescope.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/9b/The_28-inch_Telescope.jpg/440px-The_28-inch_Telescope.jpg 2x" data-file-width="724" data-file-height="1418" /></a><figcaption>The Greenwich 28-inch (71 cm) refractor is a popular tourist attraction in 21st century London.</figcaption></figure></div></div> <ul><li><a href="/wiki/Alvan_Clark_%26_Sons" title="Alvan Clark & Sons">Alvan Clark</a></li> <li>Brashear<sup id="cite_ref-21" class="reference"><a href="#cite_note-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup></li> <li><a href="/wiki/Chance_Brothers" title="Chance Brothers">Chance Brothers</a></li> <li><a href="/wiki/Robert-Agla%C3%A9_Cauchoix" title="Robert-Aglaé Cauchoix">Cauchoix</a><sup id="cite_ref-22" class="reference"><a href="#cite_note-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup></li> <li><a href="/wiki/Joseph_von_Fraunhofer" title="Joseph von Fraunhofer">Fraunhofer</a><sup id="cite_ref-23" class="reference"><a href="#cite_note-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup></li> <li>Gautier</li> <li><a href="/wiki/Grubb_Parsons" title="Grubb Parsons">Grubb</a></li> <li><a href="/wiki/Paul_Henry_and_Prosper_Henry" title="Paul Henry and Prosper Henry">Henry Brothers</a></li> <li>Lerebours<sup id="cite_ref-:42_24-0" class="reference"><a href="#cite_note-:42-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup></li> <li>Tulley<sup id="cite_ref-25" class="reference"><a href="#cite_note-25"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup></li></ul> <p>Some famous 19th century doublet refractors are the <a href="/wiki/James_Lick_telescope" title="James Lick telescope">James Lick telescope</a> (91 cm/36 in) and the <a href="/wiki/Greenwich_28_inch_refractor" class="mw-redirect" title="Greenwich 28 inch refractor">Greenwich 28 inch refractor</a> (71 cm). An example of an older refractor is the <a href="/wiki/Shuckburgh_telescope" title="Shuckburgh telescope">Shuckburgh telescope</a> (dating to the late 1700s). A famous refractor was the "Trophy Telescope", presented at the 1851 <a href="/wiki/Great_Exhibition" title="Great Exhibition">Great Exhibition</a> in London. The era of the '<a href="/wiki/Great_refractor" title="Great refractor">great refractors</a>' in the 19th century saw large achromatic lenses, culminating with the largest achromatic refractor ever built, the <a href="/wiki/Great_Paris_Exhibition_Telescope_of_1900" title="Great Paris Exhibition Telescope of 1900">Great Paris Exhibition Telescope of 1900</a>.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (September 2024)">citation needed</span></a></i>]</sup> </p><p>In the <a href="/wiki/Royal_Observatory,_Greenwich" title="Royal Observatory, Greenwich">Royal Observatory, Greenwich</a> an 1838 instrument named the <a href="/wiki/Sheepshanks_equatorial" title="Sheepshanks equatorial">Sheepshanks telescope</a> includes an objective by Cauchoix.<sup id="cite_ref-26" class="reference"><a href="#cite_note-26"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup> The Sheepshanks had a 6.7-inch (17 cm) wide lens, and was the biggest telescope at Greenwich for about twenty years.<sup id="cite_ref-27" class="reference"><a href="#cite_note-27"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup> </p><p> An 1840 report from the Observatory noted of the then-new Sheepshanks telescope with the Cauchoix doublet:<sup id="cite_ref-:32_28-0" class="reference"><a href="#cite_note-:32-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup><style data-mw-deduplicate="TemplateStyles:r1244412712">.mw-parser-output .templatequote{overflow:hidden;margin:1em 0;padding:0 32px}.mw-parser-output .templatequotecite{line-height:1.5em;text-align:left;margin-top:0}@media(min-width:500px){.mw-parser-output .templatequotecite{padding-left:1.6em}}</style></p><blockquote class="templatequote"><p>The power and general goodness of this telescope make it a most welcome addition to the instruments of the observatory</p></blockquote><p>In the 1900s a noted optics maker was Zeiss.<sup id="cite_ref-:2_29-0" class="reference"><a href="#cite_note-:2-29"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup> An example of prime achievements of refractors, over 7 million people have been able to view through the 12-inch Zeiss refractor at <a href="/wiki/Griffith_Observatory" title="Griffith Observatory">Griffith Observatory</a> since its opening in 1935; this is the most people to have viewed through any telescope.<sup id="cite_ref-:2_29-1" class="reference"><a href="#cite_note-:2-29"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup> </p><p>Achromats were popular in astronomy for making star catalogs, and they required less maintenance than metal mirrors. Some famous discoveries using achromats are the planet <a href="/wiki/Neptune" title="Neptune">Neptune</a> and the <a href="/wiki/Moons_of_Mars" title="Moons of Mars">Moons of Mars</a>.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (September 2024)">citation needed</span></a></i>]</sup> </p><p>The long achromats, despite having smaller aperture than the larger reflectors, were often favored for "prestige" observatories. In the late 18th century, every few years, a larger and longer refractor would debut.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (September 2024)">citation needed</span></a></i>]</sup> </p><p>For example, the Nice Observatory debuted with 77-centimeter (30.31 in) refractor, the largest at the time, but was surpassed within only a couple of years.<sup id="cite_ref-list1914_30-0" class="reference"><a href="#cite_note-list1914-30"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Apochromatic_refractors">Apochromatic refractors</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Refracting_telescope&action=edit&section=6" title="Edit section: Apochromatic refractors"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Apochromat" title="Apochromat">Apochromat</a></div> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Apochromat.svg" class="mw-file-description"><img alt="Apochromat lens.svg" src="//upload.wikimedia.org/wikipedia/commons/thumb/9/91/Apochromat.svg/220px-Apochromat.svg.png" decoding="async" width="220" height="78" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/91/Apochromat.svg/330px-Apochromat.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/91/Apochromat.svg/440px-Apochromat.svg.png 2x" data-file-width="599" data-file-height="213" /></a><figcaption>The Apochromatic lens usually comprises three elements that bring light of three different frequencies to a common focus</figcaption></figure> <p><b>Apochromatic refractors</b> have objectives built with special, extra-low dispersion materials. They are designed to bring three wavelengths (typically red, green, and blue) into focus in the same plane. The residual color error (tertiary spectrum) can be an order of magnitude less than that of an achromatic lens.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (July 2024)">citation needed</span></a></i>]</sup> Such telescopes contain elements of <a href="/wiki/Fluorite" title="Fluorite">fluorite</a> or special, extra-low dispersion (ED) glass in the objective and produce a very crisp image that is virtually free of chromatic aberration.<sup id="cite_ref-31" class="reference"><a href="#cite_note-31"><span class="cite-bracket">[</span>31<span class="cite-bracket">]</span></a></sup> Due to the special materials needed in the fabrication, apochromatic refractors are usually more expensive than telescopes of other types with a comparable aperture. </p><p>In the 18th century, Dollond, a popular maker of doublet telescopes, also made a triplet, although they were not really as popular as the two element telescopes.<sup id="cite_ref-:4_18-5" class="reference"><a href="#cite_note-:4-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> </p><p>One of the famous triplet objectives is the <a href="/wiki/Cooke_triplet" title="Cooke triplet">Cooke triplet</a>, noted for being able to correct the Seidal aberrations.<sup id="cite_ref-32" class="reference"><a href="#cite_note-32"><span class="cite-bracket">[</span>32<span class="cite-bracket">]</span></a></sup> It is recognized as one of the most important <a href="/wiki/Objective_(optics)" title="Objective (optics)">objective</a> designs in the field of photography.<sup id="cite_ref-33" class="reference"><a href="#cite_note-33"><span class="cite-bracket">[</span>33<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-:1_34-0" class="reference"><a href="#cite_note-:1-34"><span class="cite-bracket">[</span>34<span class="cite-bracket">]</span></a></sup> The Cooke triplet can correct, with only three elements, for one wavelength, <a href="/wiki/Spherical_aberration" title="Spherical aberration">spherical aberration</a>, <a href="/wiki/Coma_(optics)" title="Coma (optics)">coma</a>, <a href="/wiki/Astigmatism_(optical_systems)" title="Astigmatism (optical systems)">astigmatism</a>, <a href="/wiki/Field_curvature" class="mw-redirect" title="Field curvature">field curvature</a>, and <a href="/wiki/Distortion_(optics)" title="Distortion (optics)">distortion</a>.<sup id="cite_ref-:1_34-1" class="reference"><a href="#cite_note-:1-34"><span class="cite-bracket">[</span>34<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Technical_considerations">Technical considerations</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Refracting_telescope&action=edit&section=7" title="Edit section: Technical considerations"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Yerkes_Observatory_Astro4p7.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/d/dc/Yerkes_Observatory_Astro4p7.jpg/220px-Yerkes_Observatory_Astro4p7.jpg" decoding="async" width="220" height="136" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/dc/Yerkes_Observatory_Astro4p7.jpg/330px-Yerkes_Observatory_Astro4p7.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/d/dc/Yerkes_Observatory_Astro4p7.jpg/440px-Yerkes_Observatory_Astro4p7.jpg 2x" data-file-width="2021" data-file-height="1248" /></a><figcaption>The 102 centimetres (40 in) refractor, at <a href="/wiki/Yerkes_Observatory" title="Yerkes Observatory">Yerkes Observatory</a>, the largest achromatic refractor ever put into astronomical use (photo taken on 6 May 1921, as Einstein was visiting)</figcaption></figure> <p>Refractors suffer from residual <a href="/wiki/Chromatic_aberration" title="Chromatic aberration">chromatic</a> and <a href="/wiki/Spherical_aberration" title="Spherical aberration">spherical aberration</a>. This affects shorter <a href="/wiki/F-number#Focal_ratio" title="F-number">focal ratios</a> more than longer ones. An <style data-mw-deduplicate="TemplateStyles:r1263863036">.mw-parser-output span.fnumber,.mw-parser-output .fnumber-fallback{display:inline-block;white-space:nowrap;width:max-content}.mw-parser-output span.fnumber::first-letter,.mw-parser-output .fnumber-fallback .first-letter{font-style:italic;font-family:Trebuchet MS,Candara,Georgia,Calibri,Corbel,serif}</style><a href="/wiki/F-number" title="F-number"><span class="fnumber-fallback"><span class="first-letter">f</span>/6</span></a> achromatic refractor is likely to show considerable color fringing (generally a purple halo around bright objects); an <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1263863036"><span class="fnumber-fallback"><span class="first-letter">f</span>/</span>16 achromat has much less color fringing. </p><p>In very large apertures, there is also a problem of <a href="/wiki/Lens_sag" title="Lens sag">lens sagging</a>, a result of <a href="/wiki/Gravity" title="Gravity">gravity</a> deforming <a href="/wiki/Glass" title="Glass">glass</a>. Since a lens can only be held in place by its edge, the center of a large lens sags due to gravity, distorting the images it produces. The largest practical lens size in a refracting telescope is around 1 meter (39 in).<sup id="cite_ref-35" class="reference"><a href="#cite_note-35"><span class="cite-bracket">[</span>35<span class="cite-bracket">]</span></a></sup> </p><p>There is a further problem of glass defects, striae or small <a href="/wiki/Air_bubble" class="mw-redirect" title="Air bubble">air bubbles</a> trapped within the glass. In addition, glass is <a href="/wiki/Opacity_(optics)" class="mw-redirect" title="Opacity (optics)">opaque</a> to certain <a href="/wiki/Wavelength" title="Wavelength">wavelengths</a>, and even <a href="/wiki/Optical_spectrum" class="mw-redirect" title="Optical spectrum">visible light</a> is dimmed by reflection and absorption when it crosses the air-glass interfaces and passes through the glass itself. Most of these problems are avoided or diminished in <a href="/wiki/Reflecting_telescope" title="Reflecting telescope">reflecting telescopes</a>, which can be made in far larger apertures and which have all but replaced refractors for astronomical research. </p><p>The ISS-WAC on the <a href="/wiki/Voyager_1" title="Voyager 1">Voyager 1</a>/<a href="/wiki/Voyager_2" title="Voyager 2">2</a> used a 6 centimetres (2.4 in) lens, launched into space in the late 1970s, an example of the use of refractors in space.<sup id="cite_ref-astrov_36-0" class="reference"><a href="#cite_note-astrov-36"><span class="cite-bracket">[</span>36<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Applications_and_achievements">Applications and achievements</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Refracting_telescope&action=edit&section=8" title="Edit section: Applications and achievements"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Great_Refractor_Potsdam.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/74/Great_Refractor_Potsdam.jpg/300px-Great_Refractor_Potsdam.jpg" decoding="async" width="300" height="225" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/74/Great_Refractor_Potsdam.jpg/450px-Great_Refractor_Potsdam.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/74/Great_Refractor_Potsdam.jpg/600px-Great_Refractor_Potsdam.jpg 2x" data-file-width="2048" data-file-height="1536" /></a><figcaption> The "Große Refraktor" a double telescope with a 80cm (31.5") and 50 cm (19.5") lenses, was used to discover calcium as an interstellar medium in 1904.</figcaption></figure> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Jessica_Meir_Photography_Training.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/3/36/Jessica_Meir_Photography_Training.jpg/220px-Jessica_Meir_Photography_Training.jpg" decoding="async" width="220" height="147" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/3/36/Jessica_Meir_Photography_Training.jpg/330px-Jessica_Meir_Photography_Training.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/3/36/Jessica_Meir_Photography_Training.jpg/440px-Jessica_Meir_Photography_Training.jpg 2x" data-file-width="5568" data-file-height="3712" /></a><figcaption>Astronaut trains with camera with large lens</figcaption></figure> <p>Refracting telescopes were noted for their use in astronomy as well as for terrestrial viewing. Many early discoveries of the <a href="/wiki/Solar_System" title="Solar System">Solar System</a> were made with singlet refractors. </p><p>The use of refracting telescopic optics are ubiquitous in photography, and are also used in Earth orbit. </p><p>One of the more famous applications of the refracting telescope was when Galileo used it to discover the four largest moons of Jupiter in 1609. Furthermore, early refractors were also used several decades later to discover Titan, the largest moon of Saturn, along with three more of Saturn's moons. </p><p>In the 19th century, refracting telescopes were used for pioneering work on astrophotography and spectroscopy, and the related instrument, the heliometer, was used to calculate the distance to another star for the first time. Their modest apertures did not lead to as many discoveries and typically so small in aperture that many astronomical objects were simply not observable until the advent of long-exposure photography, by which time the reputation and quirks of reflecting telescopes were beginning to exceed those of the refractors. Despite this, some discoveries include the Moons of Mars, a fifth Moon of Jupiter, and many double star discoveries including Sirius (the Dog star). Refractors were often used for positional astronomy, besides from the other uses in photography and terrestrial viewing. </p> <figure class="mw-default-size mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:Spyglass.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/c/c2/Spyglass.jpg/220px-Spyglass.jpg" decoding="async" width="220" height="490" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/c/c2/Spyglass.jpg/330px-Spyglass.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/c/c2/Spyglass.jpg/440px-Spyglass.jpg 2x" data-file-width="719" data-file-height="1600" /></a><figcaption>Touristic telescope pointed to Matterhorn in Switzerland</figcaption></figure> <dl><dt>Singlets</dt></dl> <p>The Galilean moons and many other moons of the solar system, were discovered with single-element objectives and aerial telescopes. </p><p><a href="/wiki/Galileo_Galilei" title="Galileo Galilei">Galileo Galilei</a>'s discovered the <a href="/wiki/Galilean_satellites" class="mw-redirect" title="Galilean satellites">Galilean satellites</a> of Jupiter in 1610 with a refracting telescope.<sup id="cite_ref-Bakich_2000_37-0" class="reference"><a href="#cite_note-Bakich_2000-37"><span class="cite-bracket">[</span>37<span class="cite-bracket">]</span></a></sup> </p><p>The planet Saturn's moon, <a href="/wiki/Titan_(moon)" title="Titan (moon)">Titan</a>, was discovered on March 25, 1655, by the Dutch astronomer <a href="/wiki/Christiaan_Huygens" title="Christiaan Huygens">Christiaan Huygens</a>.<sup id="cite_ref-38" class="reference"><a href="#cite_note-38"><span class="cite-bracket">[</span>38<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-39" class="reference"><a href="#cite_note-39"><span class="cite-bracket">[</span>39<span class="cite-bracket">]</span></a></sup> </p> <dl><dt>Doublets</dt></dl> <p>In 1861, the brightest star in the night sky, Sirius, was found to have smaller stellar companion using the 18 and half-inch Dearborn refracting telescope. </p><p>By the 18th century refractors began to have major competition from reflectors, which could be made quite large and did not normally suffer from the same inherent problem with chromatic aberration. Nevertheless, the astronomical community continued to use doublet refractors of modest aperture in comparison to modern instruments. Noted discoveries include the <a href="/wiki/Moons_of_Mars" title="Moons of Mars">Moons of Mars</a> and a fifth moon of Jupiter, <a href="/wiki/Amalthea_(moon)" title="Amalthea (moon)">Amalthea</a>. </p><p><a href="/wiki/Asaph_Hall" title="Asaph Hall">Asaph Hall</a> discovered <a href="/wiki/Deimos_(moon)" title="Deimos (moon)">Deimos</a> on 12 August 1877 at about 07:48 <a href="/wiki/Coordinated_Universal_Time" title="Coordinated Universal Time">UTC</a> and <a href="/wiki/Phobos_(moon)" title="Phobos (moon)">Phobos</a> on 18 August 1877, at the <a href="/wiki/US_Naval_Observatory" class="mw-redirect" title="US Naval Observatory">US Naval Observatory</a> in <a href="/wiki/Washington,_D.C." title="Washington, D.C.">Washington, D.C.</a>, at about 09:14 <a href="/wiki/GMT" class="mw-redirect" title="GMT">GMT</a> (contemporary sources, using the pre-1925 <a href="/wiki/Astronomical_day" title="Astronomical day">astronomical convention</a> that began the day at noon,<sup id="cite_ref-40" class="reference"><a href="#cite_note-40"><span class="cite-bracket">[</span>40<span class="cite-bracket">]</span></a></sup> give the time of discovery as 11 August 14:40 and 17 August 16:06 <a href="/wiki/Washington_mean_time" class="mw-redirect" title="Washington mean time">Washington mean time</a> respectively).<sup id="cite_ref-41" class="reference"><a href="#cite_note-41"><span class="cite-bracket">[</span>41<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-42" class="reference"><a href="#cite_note-42"><span class="cite-bracket">[</span>42<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Morley1989_43-0" class="reference"><a href="#cite_note-Morley1989-43"><span class="cite-bracket">[</span>43<span class="cite-bracket">]</span></a></sup> </p><p>The telescope used for the discovery was the 26-inch (66 cm) refractor (telescope with a lens) then located at <a href="/wiki/Foggy_Bottom" title="Foggy Bottom">Foggy Bottom</a>.<sup id="cite_ref-44" class="reference"><a href="#cite_note-44"><span class="cite-bracket">[</span>44<span class="cite-bracket">]</span></a></sup> In 1893 the lens was remounted and put in a new dome, where it remains into the 21st century.<sup id="cite_ref-45" class="reference"><a href="#cite_note-45"><span class="cite-bracket">[</span>45<span class="cite-bracket">]</span></a></sup> </p><p>Jupiter's moon Amalthea was discovered on 9 September 1892, by <a href="/wiki/Edward_Emerson_Barnard" title="Edward Emerson Barnard">Edward Emerson Barnard</a> using the <a href="/wiki/James_Lick_telescope" title="James Lick telescope">36 inches (91 cm) refractor telescope</a> at <a href="/wiki/Lick_Observatory" title="Lick Observatory">Lick Observatory</a>.<sup id="cite_ref-46" class="reference"><a href="#cite_note-46"><span class="cite-bracket">[</span>46<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Observatory1894_47-0" class="reference"><a href="#cite_note-Observatory1894-47"><span class="cite-bracket">[</span>47<span class="cite-bracket">]</span></a></sup> It was discovered by direct visual observation with the doublet-lens refractor.<sup id="cite_ref-Bakich_2000_37-1" class="reference"><a href="#cite_note-Bakich_2000-37"><span class="cite-bracket">[</span>37<span class="cite-bracket">]</span></a></sup> </p><p>In 1904, one of the discoveries made using Great Refractor of Potsdam (a double telescope with two doublets) was of the <a href="/wiki/Interstellar_medium" title="Interstellar medium">interstellar medium</a>.<sup id="cite_ref-:5_48-0" class="reference"><a href="#cite_note-:5-48"><span class="cite-bracket">[</span>48<span class="cite-bracket">]</span></a></sup> The astronomer <a href="/wiki/Johannes_Franz_Hartmann" title="Johannes Franz Hartmann">Professor Hartmann</a> determined from observations of the binary star <a href="/wiki/Mintaka" title="Mintaka">Mintaka</a> in Orion, that there was the element <a href="/wiki/Calcium" title="Calcium">calcium</a> in the intervening space.<sup id="cite_ref-:5_48-1" class="reference"><a href="#cite_note-:5-48"><span class="cite-bracket">[</span>48<span class="cite-bracket">]</span></a></sup> </p> <dl><dt>Triplets</dt></dl> <p>Planet <a href="/wiki/Pluto" title="Pluto">Pluto</a> was discovered by looking at photographs (i.e. 'plates' in astronomy vernacular) in a <a href="/wiki/Blink_comparator" title="Blink comparator">blink comparator</a> taken with a refracting telescope, an astrograph with a 3 element 13-inch lens.<sup id="cite_ref-49" class="reference"><a href="#cite_note-49"><span class="cite-bracket">[</span>49<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-50" class="reference"><a href="#cite_note-50"><span class="cite-bracket">[</span>50<span class="cite-bracket">]</span></a></sup> </p> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">For a chronological guide, see <a href="/wiki/Timeline_of_discovery_of_Solar_System_planets_and_their_moons" title="Timeline of discovery of Solar System planets and their moons">Timeline of discovery of Solar System planets and their moons</a>.</div> <div class="mw-heading mw-heading2"><h2 id="List_of_the_largest_refracting_telescopes">List of the largest refracting telescopes</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Refracting_telescope&action=edit&section=9" title="Edit section: List of the largest refracting telescopes"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Chicago%27s_Great_Telescope_(3573567148).jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/8e/Chicago%27s_Great_Telescope_%283573567148%29.jpg/220px-Chicago%27s_Great_Telescope_%283573567148%29.jpg" decoding="async" width="220" height="176" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/8e/Chicago%27s_Great_Telescope_%283573567148%29.jpg/330px-Chicago%27s_Great_Telescope_%283573567148%29.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/8e/Chicago%27s_Great_Telescope_%283573567148%29.jpg/440px-Chicago%27s_Great_Telescope_%283573567148%29.jpg 2x" data-file-width="700" data-file-height="559" /></a><figcaption>The Yerkes Great refractor mounted at the 1893 World's Fair in Chicago; the tallest, longest, and biggest aperture refractor up to that time.</figcaption></figure> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Refraktor_Wien_Kerschbaum_1.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/6/67/Refraktor_Wien_Kerschbaum_1.jpg/220px-Refraktor_Wien_Kerschbaum_1.jpg" decoding="async" width="220" height="165" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/67/Refraktor_Wien_Kerschbaum_1.jpg/330px-Refraktor_Wien_Kerschbaum_1.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/67/Refraktor_Wien_Kerschbaum_1.jpg/440px-Refraktor_Wien_Kerschbaum_1.jpg 2x" data-file-width="1000" data-file-height="750" /></a><figcaption>The 68 <a href="/wiki/Centimetre" title="Centimetre">cm</a> (27 in) refractor at the <a href="/wiki/Vienna_Observatory" title="Vienna Observatory">Vienna University Observatory</a></figcaption></figure> <p>Examples of some of the largest achromatic refracting telescopes, over 60 cm (24 in) diameter. </p> <ul><li><a href="/wiki/Great_Paris_Exhibition_Telescope_of_1900" title="Great Paris Exhibition Telescope of 1900">Great Paris Exhibition Telescope of 1900</a> (1.25 m or 49 in) – dismantled after exhibition</li> <li><a href="/wiki/Yerkes_Observatory" title="Yerkes Observatory">Yerkes Observatory</a> (101.6 cm or 40 in)</li> <li><a href="/wiki/Swedish_Solar_Telescope" title="Swedish Solar Telescope">Swedish 1-m Solar Telescope</a> (98 cm or 39 in)</li> <li><a href="/wiki/Lick_Observatory" title="Lick Observatory">Lick Observatory</a> (91 cm or 36 in)</li> <li><a href="/wiki/Paris_Observatory" title="Paris Observatory">Paris Observatory</a> <a href="/wiki/Meudon_Great_Refractor" title="Meudon Great Refractor">Meudon Great Refractor</a> (83 cm (33 in), + 62 cm (24 in))</li> <li><a href="/wiki/Potsdam_Great_Refractor" title="Potsdam Great Refractor">Potsdam Great Refractor</a> (80 cm (31 in), + 50 cm (20 in))</li> <li><a href="/wiki/Nice_Observatory" title="Nice Observatory">Nice Observatory</a> (77 cm or 30 in)</li> <li><a href="/wiki/John_Wall_(inventor)" title="John Wall (inventor)">John Wall</a> (76.20 cm or 30 in) <a href="/wiki/Dialyte_lens#Dialyte_telescopes" title="Dialyte lens">dialyte</a> refracting telescope - the largest refractor built by an individual, at Hanwell Community Observatory<sup id="cite_ref-51" class="reference"><a href="#cite_note-51"><span class="cite-bracket">[</span>51<span class="cite-bracket">]</span></a></sup></li> <li><a href="/wiki/Greenwich_28_inch_refractor" class="mw-redirect" title="Greenwich 28 inch refractor">28-inch Grubb Refractor</a> at <a href="/wiki/Royal_Greenwich_Observatory" class="mw-redirect" title="Royal Greenwich Observatory">Royal Greenwich Observatory</a>, (71 cm or 28 in) aperture lens</li> <li>Great Refractor of <a href="/wiki/Vienna_Observatory" title="Vienna Observatory">Vienna Observatory</a>, (69 cm or 27 in)</li> <li><a href="/wiki/Archenhold_Observatory" title="Archenhold Observatory">Archenhold Observatory</a> – the longest refracting telescope ever built (68 cm or 27 in × 21 m or 69 ft focal length)</li> <li>United States Naval Observatory refractor, (66 cm or 26 in)</li> <li><a href="/wiki/Newall_Refractor" class="mw-redirect" title="Newall Refractor">Newall refractor</a> at the <a href="/wiki/National_Observatory_of_Athens" title="National Observatory of Athens">National Observatory of Athens</a> (62.5 cm or 24.6 in)</li> <li><a href="/wiki/Lowell_Observatory" title="Lowell Observatory">Lowell Observatory</a> (61 cm or 24 in)</li></ul> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Refracting_telescope&action=edit&section=10" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Astrograph" title="Astrograph">Astrograph</a></li> <li><a href="/wiki/Baden-Powell%27s_unilens" title="Baden-Powell's unilens">Baden-Powell's unilens</a></li> <li><a href="/wiki/Catadioptric_telescope" class="mw-redirect" title="Catadioptric telescope">Catadioptric telescopes</a></li> <li><a href="/wiki/List_of_largest_optical_refracting_telescopes" title="List of largest optical refracting telescopes">List of largest optical refracting telescopes</a></li> <li><a href="/wiki/List_of_largest_optical_telescopes_historically" title="List of largest optical telescopes historically">List of largest optical telescopes historically</a></li> <li><a href="/wiki/List_of_telescope_types" title="List of telescope types">List of telescope types</a></li> <li><a href="/wiki/Reflecting_telescope" title="Reflecting telescope">Reflecting telescope</a></li> <li><a href="/wiki/Star_diagonal" title="Star diagonal">Star diagonal</a></li> <li><a href="/wiki/Heliometer" title="Heliometer">Heliometer</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Refracting_telescope&action=edit&section=11" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.northern-stars.com/tel_magnification.htm">"Telescope Calculations"</a>. Northern Stars<span class="reference-accessdate">. Retrieved <span class="nowrap">20 December</span> 2013</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Telescope+Calculations&rft.pub=Northern+Stars&rft_id=http%3A%2F%2Fwww.northern-stars.com%2Ftel_magnification.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARefracting+telescope" class="Z3988"></span></span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text">Albert Van Helden, Sven Dupré, Rob van Gent, The Origins of the Telescope, Amsterdam University Press, 2010, pages 3-4, 15</span> </li> <li id="cite_note-:0-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-:0_3-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFScienceAstronomy" class="citation web cs1">Science, Lauren Cox 2017-12-21T03:30:00Z; Astronomy. <a rel="nofollow" class="external text" href="https://www.space.com/21950-who-invented-the-telescope.html">"Who Invented the Telescope?"</a>. <i>Space.com</i><span class="reference-accessdate">. Retrieved <span class="nowrap">26 October</span> 2019</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Space.com&rft.atitle=Who+Invented+the+Telescope%3F&rft.aulast=Science&rft.aufirst=Lauren+Cox+2017-12-21T03%3A30%3A00Z&rft.au=Astronomy&rft_id=https%3A%2F%2Fwww.space.com%2F21950-who-invented-the-telescope.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARefracting+telescope" class="Z3988"></span><span class="cs1-maint citation-comment"><code class="cs1-code">{{<a href="/wiki/Template:Cite_web" title="Template:Cite web">cite web</a>}}</code>: CS1 maint: numeric names: authors list (<a href="/wiki/Category:CS1_maint:_numeric_names:_authors_list" title="Category:CS1 maint: numeric names: authors list">link</a>)</span></span> </li> <li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text">Stephen G. Lipson, Ariel Lipson, Henry Lipson, <i>Optical Physics 4th Edition</i>, Cambridge University Press, <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-521-49345-1" title="Special:BookSources/978-0-521-49345-1">978-0-521-49345-1</a></span> </li> <li id="cite_note-:3-5"><span class="mw-cite-backlink">^ <a href="#cite_ref-:3_5-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-:3_5-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://brunelleschi.imss.fi.it/esplora/cannocchiale/dswmedia/esplora/eesplora1.html">"Galileo's telescope - The instrument"</a>. <i>Museo Galileo: Institute and Museum of the History of Science</i>. 2008<span class="reference-accessdate">. Retrieved <span class="nowrap">27 September</span> 2020</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Museo+Galileo%3A+Institute+and+Museum+of+the+History+of+Science&rft.atitle=Galileo%27s+telescope+-+The+instrument&rft.date=2008&rft_id=https%3A%2F%2Fbrunelleschi.imss.fi.it%2Fesplora%2Fcannocchiale%2Fdswmedia%2Fesplora%2Feesplora1.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARefracting+telescope" class="Z3988"></span></span> </li> <li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text">Sidereus Nuncius or The Sidereal Messenger, 1610, Galileo Galilei <i>et al.</i>, 1989, pg. 37, The University of Chicago Press, Albert van Helden tr., (History Dept. 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Patrick Moore's Practical Astronomy Series. pp. <span class="nowrap">3–</span>20. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1007%2F978-1-4419-6403-8_1">10.1007/978-1-4419-6403-8_1</a>. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1-4419-6402-1" title="Special:BookSources/978-1-4419-6402-1"><bdi>978-1-4419-6402-1</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=The+Refracting+Telescope%3A+A+Brief+History&rft.btitle=Choosing+and+Using+a+Refracting+Telescope&rft.series=Patrick+Moore%27s+Practical+Astronomy+Series&rft.pages=%3Cspan+class%3D%22nowrap%22%3E3-%3C%2Fspan%3E20&rft.date=2011&rft_id=info%3Adoi%2F10.1007%2F978-1-4419-6403-8_1&rft.isbn=978-1-4419-6402-1&rft.aulast=English&rft.aufirst=Neil&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARefracting+telescope" class="Z3988"></span></span> </li> <li id="cite_note-19"><span class="mw-cite-backlink"><b><a href="#cite_ref-19">^</a></b></span> <span class="reference-text"> <ul><li><a href="https://de.wikipedia.org/wiki/Pierre-Louis_Guinand" class="extiw" title="de:Pierre-Louis Guinand">Pierre-Louis Guinand</a> was a Swiss who in the late 1700s came up with a breakthrough for making better quality and larger glass, and in time went on to teach <a href="/wiki/Joseph_von_Fraunhofer" title="Joseph von Fraunhofer">Joseph von Fraunhofer</a> at Utzschinder's (Joseph von Utzschneider (1763-1840) glassworks, and eventually started his own optical glass works.</li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFKing2003" class="citation book cs1">King, Henry C. 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Courier Corporation. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9780486432656" title="Special:BookSources/9780486432656"><bdi>9780486432656</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+History+of+the+Telescope&rft.pub=Courier+Corporation&rft.date=2003-01-01&rft.isbn=9780486432656&rft.aulast=King&rft.aufirst=Henry+C.&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DKAWwzHlDVksC%26pg%3DPA176&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARefracting+telescope" class="Z3988"></span></li></ul> </span></li> <li id="cite_note-20"><span class="mw-cite-backlink"><b><a href="#cite_ref-20">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLankford2013" class="citation book cs1">Lankford, John (7 March 2013). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=9jyExgmZxBoC&q=Greenwich+28+inch+refractor&pg=PA520"><i>History of Astronomy: An Encyclopedia</i></a>. 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(July 2024)">page needed</span></a></i>]</sup></span> </li> <li id="cite_note-:2-29"><span class="mw-cite-backlink">^ <a href="#cite_ref-:2_29-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-:2_29-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://griffithobservatory.org/">"Griffith Observatory - Southern California's gateway to the cosmos!"</a>. <i>Griffith Observatory</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Griffith+Observatory&rft.atitle=Griffith+Observatory+-+Southern+California%27s+gateway+to+the+cosmos%21&rft_id=https%3A%2F%2Fgriffithobservatory.org%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARefracting+telescope" class="Z3988"></span></span> </li> <li id="cite_note-list1914-30"><span class="mw-cite-backlink"><b><a href="#cite_ref-list1914_30-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFHollis1914" class="citation journal cs1">Hollis, H. 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Springer Science & Business Media. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9781461510512" title="Special:BookSources/9781461510512"><bdi>9781461510512</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Classical+and+Evolutionary+Algorithms+in+the+Optimization+of+Optical+Systems&rft.pub=Springer+Science+%26+Business+Media&rft.date=2012-12-06&rft.isbn=9781461510512&rft.aulast=Vasiljevic&rft.aufirst=Darko&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DczjUBwAAQBAJ%26q%3D%2522Cooke%2Btriplet%2522%2B-wikipedia%26pg%3DPA187&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARefracting+telescope" class="Z3988"></span></span> </li> <li id="cite_note-:1-34"><span class="mw-cite-backlink">^ <a href="#cite_ref-:1_34-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-:1_34-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFVasiljević2002" class="citation cs2">Vasiljević, Darko (2002), "The Cooke triplet optimizations", in Vasiljević, Darko (ed.), <i>Classical and Evolutionary Algorithms in the Optimization of Optical Systems</i>, Springer US, pp. <span class="nowrap">187–</span>211, <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1007%2F978-1-4615-1051-2_13">10.1007/978-1-4615-1051-2_13</a>, <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9781461510512" title="Special:BookSources/9781461510512"><bdi>9781461510512</bdi></a></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=The+Cooke+triplet+optimizations&rft.btitle=Classical+and+Evolutionary+Algorithms+in+the+Optimization+of+Optical+Systems&rft.pages=%3Cspan+class%3D%22nowrap%22%3E187-%3C%2Fspan%3E211&rft.pub=Springer+US&rft.date=2002&rft_id=info%3Adoi%2F10.1007%2F978-1-4615-1051-2_13&rft.isbn=9781461510512&rft.aulast=Vasiljevi%C4%87&rft.aufirst=Darko&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARefracting+telescope" class="Z3988"></span></span> </li> <li id="cite_note-35"><span class="mw-cite-backlink"><b><a href="#cite_ref-35">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFStan_Gibilisco2002" class="citation book cs1">Stan Gibilisco (2002). <span class="id-lock-registration" title="Free registration required"><a rel="nofollow" class="external text" href="https://archive.org/details/physicsdemystifi0000gibi"><i>Physics Demystified</i></a></span>. 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The University Press. p. 7–.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=A+Brief+Account+of+the+Lick+Observatory+of+the+University+of+California&rft.pages=7-&rft.pub=The+University+Press&rft.date=1894&rft.au=Lick+Observatory&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DBbA2AQAAIAAJ%26pg%3DRA7-PA27&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARefracting+telescope" class="Z3988"></span></span> </li> <li id="cite_note-:5-48"><span class="mw-cite-backlink">^ <a href="#cite_ref-:5_48-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-:5_48-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFKanipe2011" class="citation book cs1">Kanipe, Jeff (27 January 2011). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=VYvQ_8I_kTwC&q=hartmann+interstellar+matter+potsdam&pg=PA154"><i>The Cosmic Connection: How Astronomical Events Impact Life on Earth</i></a>. Prometheus Books. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9781591028826" title="Special:BookSources/9781591028826"><bdi>9781591028826</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Cosmic+Connection%3A+How+Astronomical+Events+Impact+Life+on+Earth&rft.pub=Prometheus+Books&rft.date=2011-01-27&rft.isbn=9781591028826&rft.aulast=Kanipe&rft.aufirst=Jeff&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DVYvQ_8I_kTwC%26q%3Dhartmann%2Binterstellar%2Bmatter%2Bpotsdam%26pg%3DPA154&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARefracting+telescope" class="Z3988"></span></span> </li> <li id="cite_note-49"><span class="mw-cite-backlink"><b><a href="#cite_ref-49">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://lowell.edu/history/the-pluto-telescope/">"The Pluto Telescope"</a>. <i>Lowell Observatory</i><span class="reference-accessdate">. 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title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=John+Wall+refractor+%26%23124%3B+Hanwell+Community+Observatory&rft_id=http%3A%2F%2Fwww.hanwellobservatory.org.uk%2Ftelescopes%2Fjohn-wall&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARefracting+telescope" class="Z3988"></span></span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Refracting_telescope&action=edit&section=12" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1235681985">.mw-parser-output .side-box{margin:4px 0;box-sizing:border-box;border:1px solid #aaa;font-size:88%;line-height:1.25em;background-color:var(--background-color-interactive-subtle,#f8f9fa);display:flow-root}.mw-parser-output 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