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class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Right ascension</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 74 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-74" 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">74 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-af mw-list-item"><a href="https://af.wikipedia.org/wiki/Regte_klimming" title="Regte klimming – Afrikaans" lang="af" hreflang="af" data-title="Regte klimming" data-language-autonym="Afrikaans" data-language-local-name="Afrikaans" class="interlanguage-link-target"><span>Afrikaans</span></a></li><li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D9%85%D8%B7%D9%84%D8%B9_%D9%85%D8%B3%D8%AA%D9%82%D9%8A%D9%85" title="مطلع مستقيم – Arabic" lang="ar" hreflang="ar" data-title="مطلع مستقيم" 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/Ascensi%C3%B3n_reuta" title="Ascensión reuta – Asturian" lang="ast" hreflang="ast" data-title="Ascensión reuta" data-language-autonym="Asturianu" data-language-local-name="Asturian" class="interlanguage-link-target"><span>Asturianu</span></a></li><li class="interlanguage-link interwiki-az mw-list-item"><a href="https://az.wikipedia.org/wiki/Birba%C5%9Fa_%C3%A7%C4%B1xma" title="Birbaşa çıxma – Azerbaijani" lang="az" hreflang="az" data-title="Birbaşa çıxma" data-language-autonym="Azərbaycanca" data-language-local-name="Azerbaijani" class="interlanguage-link-target"><span>Azərbaycanca</span></a></li><li class="interlanguage-link interwiki-bn mw-list-item"><a href="https://bn.wikipedia.org/wiki/%E0%A6%AC%E0%A6%BF%E0%A6%B7%E0%A7%81%E0%A6%AC%E0%A6%BE%E0%A6%82%E0%A6%B6" title="বিষুবাংশ – Bangla" lang="bn" hreflang="bn" data-title="বিষুবাংশ" 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%9F%D1%80%D0%B0%D0%BC%D0%BE%D0%B5_%D1%9E%D0%B7%D1%8B%D1%85%D0%BE%D0%B4%D0%B6%D0%B0%D0%BD%D0%BD%D0%B5" title="Прамое ўзыходжанне – Belarusian" lang="be" hreflang="be" data-title="Прамое ўзыходжанне" data-language-autonym="Беларуская" data-language-local-name="Belarusian" class="interlanguage-link-target"><span>Беларуская</span></a></li><li class="interlanguage-link interwiki-be-x-old mw-list-item"><a href="https://be-tarask.wikipedia.org/wiki/%D0%9F%D1%80%D0%BE%D1%81%D1%82%D0%B0%D0%B5_%D1%9E%D0%B7%D1%8C%D0%BD%D1%8F%D1%86%D1%8C%D1%86%D1%91" title="Простае ўзьняцьцё – Belarusian (Taraškievica orthography)" lang="be-tarask" hreflang="be-tarask" data-title="Простае ўзьняцьцё" data-language-autonym="Беларуская (тарашкевіца)" data-language-local-name="Belarusian (Taraškievica orthography)" class="interlanguage-link-target"><span>Беларуская (тарашкевіца)</span></a></li><li class="interlanguage-link interwiki-bg mw-list-item"><a href="https://bg.wikipedia.org/wiki/%D0%A0%D0%B5%D0%BA%D1%82%D0%B0%D1%81%D1%86%D0%B5%D0%BD%D0%B7%D0%B8%D1%8F" title="Ректасцензия – Bulgarian" lang="bg" hreflang="bg" data-title="Ректасцензия" data-language-autonym="Български" data-language-local-name="Bulgarian" class="interlanguage-link-target"><span>Български</span></a></li><li class="interlanguage-link interwiki-bs mw-list-item"><a href="https://bs.wikipedia.org/wiki/Rektascenzija" title="Rektascenzija – Bosnian" lang="bs" hreflang="bs" data-title="Rektascenzija" data-language-autonym="Bosanski" data-language-local-name="Bosnian" class="interlanguage-link-target"><span>Bosanski</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Ascensi%C3%B3_recta" title="Ascensió recta – Catalan" lang="ca" hreflang="ca" data-title="Ascensió recta" 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/Rektascenze" title="Rektascenze – Czech" lang="cs" hreflang="cs" data-title="Rektascenze" 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/Rektascension" title="Rektascension – Danish" lang="da" hreflang="da" data-title="Rektascension" 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/Rektaszension" title="Rektaszension – German" lang="de" hreflang="de" data-title="Rektaszension" 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/Otset%C3%B5us" title="Otsetõus – Estonian" lang="et" hreflang="et" data-title="Otsetõus" 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%9F%CF%81%CE%B8%CE%AE_%CE%B1%CE%BD%CE%B1%CF%86%CE%BF%CF%81%CE%AC" title="Ορθή αναφορά – Greek" lang="el" hreflang="el" data-title="Ορθή αναφορά" 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/Ascensi%C3%B3n_recta" title="Ascensión recta – Spanish" lang="es" hreflang="es" data-title="Ascensión recta" 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/Rektascensio" title="Rektascensio – Esperanto" lang="eo" hreflang="eo" data-title="Rektascensio" 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/Igoera_zuzen" title="Igoera zuzen – Basque" lang="eu" hreflang="eu" data-title="Igoera zuzen" 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%A8%D8%B9%D8%AF_(%D8%A7%D8%AE%D8%AA%D8%B1%D8%B4%D9%86%D8%A7%D8%B3%DB%8C)" title="بعد (اخترشناسی) – Persian" lang="fa" hreflang="fa" data-title="بعد (اخترشناسی)" 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/Ascension_droite" title="Ascension droite – French" lang="fr" hreflang="fr" data-title="Ascension droite" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-ga mw-list-item"><a href="https://ga.wikipedia.org/wiki/Dronairde" title="Dronairde – Irish" lang="ga" hreflang="ga" data-title="Dronairde" data-language-autonym="Gaeilge" data-language-local-name="Irish" class="interlanguage-link-target"><span>Gaeilge</span></a></li><li class="interlanguage-link interwiki-gl mw-list-item"><a href="https://gl.wikipedia.org/wiki/Ascensi%C3%B3n_recta" title="Ascensión recta – Galician" lang="gl" hreflang="gl" data-title="Ascensión recta" 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/%EC%A0%81%EA%B2%BD" title="적경 – Korean" lang="ko" hreflang="ko" data-title="적경" 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%88%D6%82%D5%B2%D5%AB%D5%B2_%D5%AE%D5%A1%D5%A3%D5%B8%D6%82%D5%B4" title="Ուղիղ ծագում – Armenian" lang="hy" hreflang="hy" data-title="Ուղիղ ծագում" 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%A6%E0%A4%BE%E0%A4%AF%E0%A4%BE%E0%A4%81_%E0%A4%86%E0%A4%B0%E0%A5%8B%E0%A4%B9%E0%A4%A3" title="दायाँ आरोहण – Hindi" lang="hi" hreflang="hi" data-title="दायाँ आरोहण" 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/Rektascenzija" title="Rektascenzija – Croatian" lang="hr" hreflang="hr" data-title="Rektascenzija" data-language-autonym="Hrvatski" data-language-local-name="Croatian" class="interlanguage-link-target"><span>Hrvatski</span></a></li><li class="interlanguage-link interwiki-ig mw-list-item"><a href="https://ig.wikipedia.org/wiki/Nr%E1%BB%8Bgo_aka_nri" title="Nrịgo aka nri – Igbo" lang="ig" hreflang="ig" data-title="Nrịgo aka nri" data-language-autonym="Igbo" data-language-local-name="Igbo" class="interlanguage-link-target"><span>Igbo</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Asensio_rekta" title="Asensio rekta – Indonesian" lang="id" hreflang="id" data-title="Asensio rekta" data-language-autonym="Bahasa Indonesia" data-language-local-name="Indonesian" class="interlanguage-link-target"><span>Bahasa Indonesia</span></a></li><li class="interlanguage-link interwiki-is mw-list-item"><a href="https://is.wikipedia.org/wiki/T%C3%ADmahorn" title="Tímahorn – Icelandic" lang="is" hreflang="is" data-title="Tímahorn" data-language-autonym="Íslenska" data-language-local-name="Icelandic" class="interlanguage-link-target"><span>Íslenska</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Ascensione_retta" title="Ascensione retta – Italian" lang="it" hreflang="it" data-title="Ascensione retta" 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%A2%D7%9C%D7%99%D7%99%D7%94_%D7%99%D7%A9%D7%A8%D7%94" title="עלייה ישרה – Hebrew" lang="he" hreflang="he" data-title="עלייה ישרה" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-ka mw-list-item"><a href="https://ka.wikipedia.org/wiki/%E1%83%9E%E1%83%98%E1%83%A0%E1%83%93%E1%83%90%E1%83%9E%E1%83%98%E1%83%A0%E1%83%98_%E1%83%90%E1%83%A6%E1%83%95%E1%83%9A%E1%83%94%E1%83%9C%E1%83%90" title="პირდაპირი აღვლენა – Georgian" lang="ka" hreflang="ka" data-title="პირდაპირი აღვლენა" data-language-autonym="ქართული" data-language-local-name="Georgian" class="interlanguage-link-target"><span>ქართული</span></a></li><li class="interlanguage-link interwiki-kk mw-list-item"><a href="https://kk.wikipedia.org/wiki/%D0%A2%D1%83%D1%80%D0%B0_%D0%BA%D3%A9%D1%82%D0%B5%D1%80%D1%96%D0%BB%D1%83" title="Тура көтерілу – Kazakh" lang="kk" hreflang="kk" data-title="Тура көтерілу" data-language-autonym="Қазақша" data-language-local-name="Kazakh" class="interlanguage-link-target"><span>Қазақша</span></a></li><li class="interlanguage-link interwiki-la mw-list-item"><a href="https://la.wikipedia.org/wiki/Ascensio_recta" title="Ascensio recta – Latin" lang="la" hreflang="la" data-title="Ascensio recta" data-language-autonym="Latina" data-language-local-name="Latin" class="interlanguage-link-target"><span>Latina</span></a></li><li class="interlanguage-link interwiki-lv mw-list-item"><a href="https://lv.wikipedia.org/wiki/Rektascensija" title="Rektascensija – Latvian" lang="lv" hreflang="lv" data-title="Rektascensija" 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/Rektaszensioun" title="Rektaszensioun – Luxembourgish" lang="lb" hreflang="lb" data-title="Rektaszensioun" data-language-autonym="Lëtzebuergesch" data-language-local-name="Luxembourgish" class="interlanguage-link-target"><span>Lëtzebuergesch</span></a></li><li class="interlanguage-link interwiki-lt mw-list-item"><a href="https://lt.wikipedia.org/wiki/Rektascensija" title="Rektascensija – Lithuanian" lang="lt" hreflang="lt" data-title="Rektascensija" data-language-autonym="Lietuvių" data-language-local-name="Lithuanian" class="interlanguage-link-target"><span>Lietuvių</span></a></li><li class="interlanguage-link interwiki-hu mw-list-item"><a href="https://hu.wikipedia.org/wiki/Rektaszcenzi%C3%B3" title="Rektaszcenzió – Hungarian" lang="hu" hreflang="hu" data-title="Rektaszcenzió" data-language-autonym="Magyar" data-language-local-name="Hungarian" class="interlanguage-link-target"><span>Magyar</span></a></li><li class="interlanguage-link interwiki-mk mw-list-item"><a href="https://mk.wikipedia.org/wiki/%D0%A0%D0%B5%D0%BA%D1%82%D0%B0%D1%81%D1%86%D0%B5%D0%BD%D0%B7%D0%B8%D1%98%D0%B0" title="Ректасцензија – Macedonian" lang="mk" hreflang="mk" data-title="Ректасцензија" 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%96%E0%B4%97%E0%B5%8B%E0%B4%B3%E0%B4%B0%E0%B5%87%E0%B4%96%E0%B4%BE%E0%B4%82%E0%B4%B6%E0%B4%82" title="ഖഗോളരേഖാംശം – Malayalam" lang="ml" hreflang="ml" data-title="ഖഗോളരേഖാംശം" data-language-autonym="മലയാളം" data-language-local-name="Malayalam" class="interlanguage-link-target"><span>മലയാളം</span></a></li><li class="interlanguage-link interwiki-mr mw-list-item"><a href="https://mr.wikipedia.org/wiki/%E0%A4%B5%E0%A4%BF%E0%A4%B7%E0%A5%81%E0%A4%B5%E0%A4%BE%E0%A4%82%E0%A4%B6" title="विषुवांश – Marathi" lang="mr" hreflang="mr" data-title="विषुवांश" data-language-autonym="मराठी" data-language-local-name="Marathi" class="interlanguage-link-target"><span>मराठी</span></a></li><li class="interlanguage-link interwiki-ms mw-list-item"><a href="https://ms.wikipedia.org/wiki/Jarak_hamal" title="Jarak hamal – Malay" lang="ms" hreflang="ms" data-title="Jarak hamal" 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/Rechte_klimming" title="Rechte klimming – Dutch" lang="nl" hreflang="nl" data-title="Rechte klimming" 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/%E8%B5%A4%E7%B5%8C" title="赤経 – Japanese" lang="ja" hreflang="ja" data-title="赤経" 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-frr mw-list-item"><a href="https://frr.wikipedia.org/wiki/Rektaszension" title="Rektaszension – Northern Frisian" lang="frr" hreflang="frr" data-title="Rektaszension" data-language-autonym="Nordfriisk" data-language-local-name="Northern Frisian" class="interlanguage-link-target"><span>Nordfriisk</span></a></li><li class="interlanguage-link interwiki-no mw-list-item"><a href="https://no.wikipedia.org/wiki/Rektascensjon" title="Rektascensjon – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Rektascensjon" 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/Rektasensjon" title="Rektasensjon – Norwegian Nynorsk" lang="nn" hreflang="nn" data-title="Rektasensjon" 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/Ascension_drecha" title="Ascension drecha – Occitan" lang="oc" hreflang="oc" data-title="Ascension drecha" data-language-autonym="Occitan" data-language-local-name="Occitan" class="interlanguage-link-target"><span>Occitan</span></a></li><li class="interlanguage-link interwiki-pnb mw-list-item"><a href="https://pnb.wikipedia.org/wiki/%D8%A7%D8%B3%D9%85%D8%A7%D9%86%DB%8C_%DA%A9%DA%BE%DA%91%DB%8C_%D9%84%DB%8C%DA%A9" title="اسمانی کھڑی لیک – Western Punjabi" lang="pnb" hreflang="pnb" data-title="اسمانی کھڑی لیک" data-language-autonym="پنجابی" data-language-local-name="Western Punjabi" class="interlanguage-link-target"><span>پنجابی</span></a></li><li class="interlanguage-link interwiki-nds mw-list-item"><a href="https://nds.wikipedia.org/wiki/Rektaszension" title="Rektaszension – Low German" lang="nds" hreflang="nds" data-title="Rektaszension" data-language-autonym="Plattdüütsch" data-language-local-name="Low German" class="interlanguage-link-target"><span>Plattdüütsch</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Rektascensja" title="Rektascensja – Polish" lang="pl" hreflang="pl" data-title="Rektascensja" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/Ascens%C3%A3o_reta" title="Ascensão reta – Portuguese" lang="pt" hreflang="pt" data-title="Ascensão reta" 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/Ascensie_dreapt%C4%83" title="Ascensie dreaptă – Romanian" lang="ro" hreflang="ro" data-title="Ascensie dreaptă" data-language-autonym="Română" data-language-local-name="Romanian" class="interlanguage-link-target"><span>Română</span></a></li><li class="interlanguage-link interwiki-ru badge-Q17559452 badge-recommendedarticle mw-list-item" title="recommended article"><a href="https://ru.wikipedia.org/wiki/%D0%9F%D1%80%D1%8F%D0%BC%D0%BE%D0%B5_%D0%B2%D0%BE%D1%81%D1%85%D0%BE%D0%B6%D0%B4%D0%B5%D0%BD%D0%B8%D0%B5" title="Прямое восхождение – Russian" lang="ru" hreflang="ru" data-title="Прямое восхождение" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-sco mw-list-item"><a href="https://sco.wikipedia.org/wiki/Richt_ascension" title="Richt ascension – Scots" lang="sco" hreflang="sco" data-title="Richt ascension" data-language-autonym="Scots" data-language-local-name="Scots" class="interlanguage-link-target"><span>Scots</span></a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/Right_ascension" title="Right ascension – Simple English" lang="en-simple" hreflang="en-simple" data-title="Right ascension" data-language-autonym="Simple English" data-language-local-name="Simple English" class="interlanguage-link-target"><span>Simple English</span></a></li><li class="interlanguage-link interwiki-sk mw-list-item"><a href="https://sk.wikipedia.org/wiki/Rektascenzia" title="Rektascenzia – Slovak" lang="sk" hreflang="sk" data-title="Rektascenzia" 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/Rektascenzija" title="Rektascenzija – Slovenian" lang="sl" hreflang="sl" data-title="Rektascenzija" data-language-autonym="Slovenščina" data-language-local-name="Slovenian" class="interlanguage-link-target"><span>Slovenščina</span></a></li><li class="interlanguage-link interwiki-sr mw-list-item"><a href="https://sr.wikipedia.org/wiki/Rektascenzija" title="Rektascenzija – Serbian" lang="sr" hreflang="sr" data-title="Rektascenzija" data-language-autonym="Српски / srpski" data-language-local-name="Serbian" class="interlanguage-link-target"><span>Српски / srpski</span></a></li><li class="interlanguage-link interwiki-sh mw-list-item"><a href="https://sh.wikipedia.org/wiki/Rektascenzija" title="Rektascenzija – Serbo-Croatian" lang="sh" hreflang="sh" data-title="Rektascenzija" data-language-autonym="Srpskohrvatski / српскохрватски" data-language-local-name="Serbo-Croatian" class="interlanguage-link-target"><span>Srpskohrvatski / српскохрватски</span></a></li><li class="interlanguage-link interwiki-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/Rektaskensio" title="Rektaskensio – Finnish" lang="fi" hreflang="fi" data-title="Rektaskensio" data-language-autonym="Suomi" data-language-local-name="Finnish" class="interlanguage-link-target"><span>Suomi</span></a></li><li class="interlanguage-link interwiki-sv mw-list-item"><a href="https://sv.wikipedia.org/wiki/Rektascension" title="Rektascension – Swedish" lang="sv" hreflang="sv" data-title="Rektascension" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target"><span>Svenska</span></a></li><li class="interlanguage-link interwiki-tl mw-list-item"><a href="https://tl.wikipedia.org/wiki/Kanang_asensiyon" title="Kanang asensiyon – Tagalog" lang="tl" hreflang="tl" data-title="Kanang asensiyon" 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<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">Astronomical equivalent of longitude</div> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Ra_and_dec_demo_animation_small.gif" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/6/66/Ra_and_dec_demo_animation_small.gif" decoding="async" width="300" height="300" class="mw-file-element" data-file-width="300" data-file-height="300" /></a><figcaption> <b>Right ascension</b> and <a href="/wiki/Declination" title="Declination">declination</a> as seen on the inside of the <a href="/wiki/Celestial_sphere" title="Celestial sphere">celestial sphere</a>. The primary direction of the system is the <a href="/wiki/Equinox_(celestial_coordinates)" title="Equinox (celestial coordinates)">March equinox</a>, the ascending node of the <a href="/wiki/Ecliptic" title="Ecliptic">ecliptic</a> (red) on the <a href="/wiki/Celestial_equator" title="Celestial equator">celestial equator</a> (blue). Right ascension is measured eastward up to 24<sup>h</sup> along the celestial equator from the primary direction.</figcaption></figure> <p><b>Right ascension</b> (abbreviated <b>RA</b>; symbol <b><span class="texhtml mvar" style="font-style:italic;">α</span></b>) is the <a href="/wiki/Angular_distance" title="Angular distance">angular distance</a> of a particular point measured eastward along the <a href="/wiki/Celestial_equator" title="Celestial equator">celestial equator</a> from the <a href="/wiki/Sun" title="Sun">Sun</a> at the <a href="/wiki/Equinox_(celestial_coordinates)" title="Equinox (celestial coordinates)">March equinox</a> to the (<a href="/wiki/Hour_circle" title="Hour circle">hour circle</a> of the) point in question above the Earth.<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> When paired with <a href="/wiki/Declination" title="Declination">declination</a>, these <a href="/wiki/Celestial_coordinate_system" class="mw-redirect" title="Celestial coordinate system">astronomical coordinates</a> specify the location of a point on the <a href="/wiki/Celestial_sphere" title="Celestial sphere">celestial sphere</a> in the <a href="/wiki/Equatorial_coordinate_system" title="Equatorial coordinate system">equatorial coordinate system</a>. </p><p>An old term, <i>right ascension</i> (<a href="/wiki/Latin_language" class="mw-redirect" title="Latin language">Latin</a>: <i lang="la">ascensio recta</i>)<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> refers to the <i>ascension</i>, or the point on the celestial equator that rises with any <a href="/wiki/Celestial_object" class="mw-redirect" title="Celestial object">celestial object</a> as seen from <a href="/wiki/Earth" title="Earth">Earth</a>'s <a href="/wiki/Equator" title="Equator">equator</a>, where the celestial equator <a href="/wiki/Perpendicular" title="Perpendicular">intersects</a> the <a href="/wiki/Horizon" title="Horizon">horizon</a> at a <a href="/wiki/Right_angle" title="Right angle">right angle</a>. It contrasts with <i>oblique ascension</i>, the point on the celestial equator that rises with any celestial object as seen from most <a href="/wiki/Latitude" title="Latitude">latitudes</a> on Earth, where the celestial equator intersects the <a href="/wiki/Horizon" title="Horizon">horizon</a> at an <a href="/wiki/Oblique_angle" class="mw-redirect" title="Oblique angle">oblique angle</a>.<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Explanation">Explanation</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Right_ascension&action=edit&section=1" title="Edit section: Explanation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure typeof="mw:File/Thumb"><a href="/wiki/File:Ra_and_dec_on_celestial_sphere.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/9/98/Ra_and_dec_on_celestial_sphere.png/300px-Ra_and_dec_on_celestial_sphere.png" decoding="async" width="300" height="303" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/98/Ra_and_dec_on_celestial_sphere.png/450px-Ra_and_dec_on_celestial_sphere.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/98/Ra_and_dec_on_celestial_sphere.png/600px-Ra_and_dec_on_celestial_sphere.png 2x" data-file-width="990" data-file-height="1000" /></a><figcaption><b>Right ascension</b> (blue) and <a href="/wiki/Declination" title="Declination">declination</a> (green) as seen from outside the <a href="/wiki/Celestial_sphere" title="Celestial sphere">celestial sphere</a></figcaption></figure> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Hour_angle_still1.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/4/43/Hour_angle_still1.png/220px-Hour_angle_still1.png" decoding="async" width="220" height="220" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/43/Hour_angle_still1.png/330px-Hour_angle_still1.png 1.5x, //upload.wikimedia.org/wikipedia/commons/4/43/Hour_angle_still1.png 2x" data-file-width="400" data-file-height="400" /></a><figcaption>Various <a href="/wiki/Hour_angle" title="Hour angle">hour angles</a> are depicted here. The symbol ♈︎ marks the <a href="/wiki/Equinox" title="Equinox">March equinox</a> direction. <br />Assuming the day of the year is the March equinox: the <a href="/wiki/Sun" title="Sun">Sun</a> lies toward the grey arrow, the star marked by a green arrow will appear to rise somewhere in the east about midnight (the Earth drawn from "above" turns anticlockwise). After the observer reaches the green arrow, dawn will over-power (see blue sky <a href="/wiki/Rayleigh_scattering" title="Rayleigh scattering">Rayleigh scattering</a>) the star's light for about six hours, before it sets on the western horizon. The Right ascension of the star is about 18<sup>h</sup>. 18<sup>h</sup> means it is a March early-hours star and in <a href="/wiki/Diffuse_sky_radiation" title="Diffuse sky radiation">blue sky</a> in the morning. If 12<sup>h</sup> RA, the star would be a March all-night star as <a href="/wiki/Opposition_(planets)" class="mw-redirect" title="Opposition (planets)">opposite</a> the March equinox. If 6<sup>h</sup> RA the star would be a March late-hours star, at its high (meridian) at dusk.</figcaption></figure> <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">Main article: <a href="/wiki/Equatorial_coordinate_system" title="Equatorial coordinate system">Equatorial coordinate system</a></div> <p>Right ascension is the celestial equivalent of terrestrial <a href="/wiki/Longitude" title="Longitude">longitude</a>. Both right ascension and longitude measure an angle from a primary direction (a zero point) on an <a href="/wiki/Equator" title="Equator">equator</a>. Right ascension is measured from the Sun at the <a href="/wiki/Equinox_(celestial_coordinates)" title="Equinox (celestial coordinates)">March equinox</a> i.e. the <a href="/wiki/First_Point_of_Aries" class="mw-redirect" title="First Point of Aries">First Point of Aries</a>, which is the place on the <a href="/wiki/Celestial_sphere" title="Celestial sphere">celestial sphere</a> where the Sun crosses the <a href="/wiki/Celestial_equator" title="Celestial equator">celestial equator</a> from south to north at the March <a href="/wiki/Equinox" title="Equinox">equinox</a> and is currently located in the <a href="/wiki/Pisces_(constellation)" title="Pisces (constellation)">constellation Pisces</a>. Right ascension is measured continuously in a full circle from that alignment of Earth and Sun in space, that equinox, the measurement increasing towards the east.<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>As seen from Earth (except at the poles), objects noted to have 12<abbr title="Hours right ascension"><sup>h</sup> RA</abbr> are longest visible (appear throughout the night) at the March equinox; those with 0<abbr title="hours right ascension"><sup>h</sup> RA</abbr> (apart from the sun) do so at the September equinox. On those dates at midnight, such objects will reach ("culminate" at) their highest point (their meridian). How high depends on their declination; if 0° declination (i.e. on the <a href="/wiki/Celestial_equator" title="Celestial equator">celestial equator</a>) then at Earth's equator they are directly overhead (at <a href="/wiki/Zenith" title="Zenith">zenith</a>). </p><p>Any <a href="/wiki/Angular_unit" class="mw-redirect" title="Angular unit">angular unit</a> could have been chosen for right ascension, but it is customarily measured in hours (<sup>h</sup>), minutes (<sup>m</sup>), and seconds (<sup>s</sup>), with 24<sup>h</sup> being equivalent to a <a href="/wiki/Full_circle_(unit)" class="mw-redirect" title="Full circle (unit)">full circle</a>. Astronomers have chosen this unit to measure right ascension because they measure a star's location by timing its passage through the highest point in the sky as the <a href="/wiki/Earth%27s_rotation" title="Earth's rotation">Earth rotates</a>. The line which passes through the highest point in the sky, called the <a href="/wiki/Meridian_(astronomy)" title="Meridian (astronomy)">meridian</a>, is the projection of a longitude line onto the celestial sphere. Since a complete circle contains 24<sup>h</sup> of right ascension or 360° (<a href="/wiki/Degree_(angle)" title="Degree (angle)">degrees of arc</a>), <style data-mw-deduplicate="TemplateStyles:r1214402035">.mw-parser-output .sfrac{white-space:nowrap}.mw-parser-output .sfrac.tion,.mw-parser-output .sfrac .tion{display:inline-block;vertical-align:-0.5em;font-size:85%;text-align:center}.mw-parser-output .sfrac .num{display:block;line-height:1em;margin:0.0em 0.1em;border-bottom:1px solid}.mw-parser-output .sfrac .den{display:block;line-height:1em;margin:0.1em 0.1em}.mw-parser-output .sr-only{border:0;clip:rect(0,0,0,0);clip-path:polygon(0px 0px,0px 0px,0px 0px);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px}</style><span class="sfrac">⁠<span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den">24</span></span>⁠</span> of a circle is measured as 1<sup>h</sup> of right ascension, or 15°; <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035"><span class="sfrac">⁠<span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den">1440</span></span>⁠</span> of a circle is measured as 1<sup>m</sup> of right ascension, or <a href="/wiki/Arcminute" class="mw-redirect" title="Arcminute">15 minutes of arc</a> (also written as 15′); and <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035"><span class="sfrac">⁠<span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den">86400</span></span>⁠</span> of a circle contains 1<sup>s</sup> of right ascension, or <a href="/wiki/Arcsecond" class="mw-redirect" title="Arcsecond">15 seconds of arc</a> (also written as 15″). A full circle, measured in right-ascension units, contains <span class="nowrap">24 × 60 × 60 = <span class="nowrap"><span data-sort-value="7004864000000000000♠"></span>86<span style="margin-left:.25em;">400</span></span><sup>s</sup></span>, or <span class="nowrap">24 × 60 = <span class="nowrap"><span data-sort-value="7003144000000000000♠"></span>1<span style="margin-left:.25em;">440</span></span><sup>m</sup></span>, or 24<sup>h</sup>.<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<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">See also: <a href="/wiki/Hour_angle" title="Hour angle">Hour angle</a></div> <p>Because right ascensions are measured in hours (of <a href="/wiki/Earth%27s_rotation" title="Earth's rotation">rotation of the Earth</a>), they can be used to time the positions of objects in the sky. For example, if a star with RA = <span class="nowrap">1<sup>h</sup> 30<sup>m</sup> 00<sup>s</sup></span> is at its meridian, then a star with RA = <span class="nowrap">20<sup>h</sup> 00<sup>m</sup> 00<sup>s</sup></span> will be on the/at its meridian (at its apparent highest point) 18.5 <a href="/wiki/Sidereal_time" title="Sidereal time">sidereal hours</a> later. </p><p>Sidereal hour angle, used in <a href="/wiki/Celestial_navigation" title="Celestial navigation">celestial navigation</a>, is similar to right ascension but increases westward rather than eastward. Usually measured in degrees (°), it is the complement of right ascension with respect to 24<sup>h</sup>.<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> It is important not to confuse sidereal hour angle with the astronomical concept of <a href="/wiki/Hour_angle" title="Hour angle">hour angle</a>, which measures the angular distance of an object westward from the local <a href="/wiki/Meridian_(astronomy)" title="Meridian (astronomy)">meridian</a>. </p> <div class="mw-heading mw-heading2"><h2 id="Symbols_and_abbreviations">Symbols and abbreviations</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Right_ascension&action=edit&section=2" title="Edit section: Symbols and abbreviations"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <table class="wikitable" style="margin: 0 auto"> <tbody><tr> <th scope="col">Unit</th> <th scope="col">Value</th> <th scope="col">Symbol</th> <th scope="col"><a href="/wiki/Sexagesimal" title="Sexagesimal">Sexagesimal</a> system</th> <th scope="col">In <a href="/wiki/Radian" title="Radian">radians</a> </th></tr> <tr> <th>Hour </th> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035"><span class="sfrac">⁠<span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den">24</span></span>⁠</span> circle</td> <td align="center"><sup>h</sup></td> <td>15<a href="/wiki/Degree_symbol" title="Degree symbol">°</a></td> <td align="right"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035"><span class="sfrac">⁠<span class="tion"><span class="num"><span class="texhtml mvar" style="font-style:italic;">π</span></span><span class="sr-only">/</span><span class="den">12</span></span>⁠</span> rad </td></tr> <tr> <th>Minute </th> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035"><span class="sfrac">⁠<span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den">60</span></span>⁠</span> hour, <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035"><span class="sfrac">⁠<span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den"><span class="nowrap"><span data-sort-value="7003144000000000000♠"></span>1<span style="margin-left:.25em;">440</span></span></span></span>⁠</span> circle</td> <td align="center"><sup>m</sup></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035"><span class="sfrac">⁠<span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den">4</span></span>⁠</span>°, 15<a href="/wiki/Minute_of_arc" class="mw-redirect" title="Minute of arc">′</a></td> <td align="right"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035"><span class="sfrac">⁠<span class="tion"><span class="num"><span class="texhtml mvar" style="font-style:italic;">π</span></span><span class="sr-only">/</span><span class="den">720</span></span>⁠</span> rad </td></tr> <tr> <th>Second </th> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035"><span class="sfrac">⁠<span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den">60</span></span>⁠</span> minute, <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035"><span class="sfrac">⁠<span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den"><span class="nowrap"><span data-sort-value="7003360000000000000♠"></span>3<span style="margin-left:.25em;">600</span></span></span></span>⁠</span> hour, <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035"><span class="sfrac">⁠<span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den"><span class="nowrap"><span data-sort-value="7004864000000000000♠"></span>86<span style="margin-left:.25em;">400</span></span></span></span>⁠</span> circle</td> <td align="center"><sup>s</sup></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035"><span class="sfrac">⁠<span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den">240</span></span>⁠</span>°, <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035"><span class="sfrac">⁠<span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den">4</span></span>⁠</span>′, 15<a href="/wiki/Second_of_arc" class="mw-redirect" title="Second of arc">″</a></td> <td align="right"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035"><span class="sfrac">⁠<span class="tion"><span class="num"><span class="texhtml mvar" style="font-style:italic;">π</span></span><span class="sr-only">/</span><span class="den"><span class="nowrap"><span data-sort-value="7004432000000000000♠"></span>43<span style="margin-left:.25em;">200</span></span></span></span>⁠</span> rad </td></tr></tbody></table> <div class="mw-heading mw-heading2"><h2 id="Effects_of_precession">Effects of precession</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Right_ascension&action=edit&section=3" title="Edit section: Effects of precession"><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/Axial_precession" title="Axial precession">Axial precession</a></div> <p>The Earth's axis traces a small circle (relative to its celestial equator) slowly westward about the <a href="/wiki/Celestial_pole" title="Celestial pole">celestial poles</a>, completing one cycle in about 26,000 years. This movement, known as <a href="/wiki/Axial_precession" title="Axial precession">precession</a>, causes the coordinates of stationary celestial objects to change continuously, if rather slowly. Therefore, <a href="/wiki/Equatorial_coordinate_system" title="Equatorial coordinate system">equatorial coordinates</a> (including right ascension) are inherently relative to the year of their observation, and astronomers specify them with reference to a particular year, known as an <a href="/wiki/Epoch_(astronomy)" title="Epoch (astronomy)">epoch</a>. Coordinates from different epochs must be mathematically rotated to match each other, or to match a standard epoch.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> Right ascension for "fixed stars" on the equator increases by about 3.1 seconds per year or 5.1 minutes per century, but for fixed stars away from the equator the rate of change can be anything from negative infinity to positive infinity. (To this must be added the <a href="/wiki/Proper_motion" title="Proper motion">proper motion</a> of a star.) Over a precession cycle of 26,000 years, "fixed stars" that are far from the <a href="/wiki/Ecliptic_pole" class="mw-redirect" title="Ecliptic pole">ecliptic poles</a> increase in right ascension by 24h, or about 5.6' per century, whereas stars within 23.5° of an ecliptic pole undergo a net change of<span class="nowrap"> </span>0h. The right ascension of <a href="/wiki/Polaris" title="Polaris">Polaris</a> is increasing quickly—in AD 2000 it was 2.5h, but when it gets closest to the north celestial pole in 2100 its right ascension will be 6h. The <a href="/wiki/North_Ecliptic_Pole" class="mw-redirect" title="North Ecliptic Pole">North Ecliptic Pole</a> in <a href="/wiki/Draco_(constellation)" title="Draco (constellation)">Draco</a> and the <a href="/wiki/South_Ecliptic_Pole" class="mw-redirect" title="South Ecliptic Pole">South Ecliptic Pole</a> in <a href="/wiki/Dorado" title="Dorado">Dorado</a> are always at right ascension 18<sup>h</sup> and 6<sup>h</sup> respectively. </p><p>The currently used standard epoch is <a href="/wiki/J2000.0" class="mw-redirect" title="J2000.0">J2000.0</a>, which is January 1, 2000 at 12:00 <a href="/wiki/Terrestrial_Time" title="Terrestrial Time">TT</a>. The prefix "J" indicates that it is a <a href="/wiki/Julian_epoch" class="mw-redirect" title="Julian epoch">Julian epoch</a>. Prior to J2000.0, astronomers used the successive <a href="/wiki/Epoch_(astronomy)#Besselian_epoch" title="Epoch (astronomy)">Besselian epochs</a> B1875.0, B1900.0, and B1950.0.<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> </p> <div class="mw-heading mw-heading2"><h2 id="History">History</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Right_ascension&action=edit&section=4" title="Edit section: History"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1251242444">.mw-parser-output .ambox{border:1px solid #a2a9b1;border-left:10px solid #36c;background-color:#fbfbfb;box-sizing:border-box}.mw-parser-output .ambox+link+.ambox,.mw-parser-output .ambox+link+style+.ambox,.mw-parser-output .ambox+link+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+style+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+link+.ambox{margin-top:-1px}html body.mediawiki .mw-parser-output .ambox.mbox-small-left{margin:4px 1em 4px 0;overflow:hidden;width:238px;border-collapse:collapse;font-size:88%;line-height:1.25em}.mw-parser-output .ambox-speedy{border-left:10px solid #b32424;background-color:#fee7e6}.mw-parser-output .ambox-delete{border-left:10px solid #b32424}.mw-parser-output .ambox-content{border-left:10px solid #f28500}.mw-parser-output .ambox-style{border-left:10px solid #fc3}.mw-parser-output .ambox-move{border-left:10px solid #9932cc}.mw-parser-output .ambox-protection{border-left:10px solid #a2a9b1}.mw-parser-output .ambox .mbox-text{border:none;padding:0.25em 0.5em;width:100%}.mw-parser-output .ambox .mbox-image{border:none;padding:2px 0 2px 0.5em;text-align:center}.mw-parser-output .ambox .mbox-imageright{border:none;padding:2px 0.5em 2px 0;text-align:center}.mw-parser-output .ambox .mbox-empty-cell{border:none;padding:0;width:1px}.mw-parser-output .ambox .mbox-image-div{width:52px}@media(min-width:720px){.mw-parser-output .ambox{margin:0 10%}}@media print{body.ns-0 .mw-parser-output .ambox{display:none!important}}</style><table class="box-More_citations_needed_section plainlinks metadata ambox ambox-content ambox-Refimprove" role="presentation"><tbody><tr><td class="mbox-image"><div class="mbox-image-div"><span typeof="mw:File"><a href="/wiki/File:Question_book-new.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/50px-Question_book-new.svg.png" decoding="async" width="50" height="39" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/75px-Question_book-new.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/100px-Question_book-new.svg.png 2x" data-file-width="512" data-file-height="399" /></a></span></div></td><td class="mbox-text"><div class="mbox-text-span">This section <b>needs additional citations for <a href="/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability">verification</a></b>.<span class="hide-when-compact"> Please help <a href="/wiki/Special:EditPage/Right_ascension" title="Special:EditPage/Right ascension">improve this article</a> by <a href="/wiki/Help:Referencing_for_beginners" title="Help:Referencing for beginners">adding citations to reliable sources</a> in this section. Unsourced material may be challenged and removed.</span> <span class="date-container"><i>(<span class="date">May 2012</span>)</i></span><span class="hide-when-compact"><i> (<small><a href="/wiki/Help:Maintenance_template_removal" title="Help:Maintenance template removal">Learn how and when to remove this message</a></small>)</i></span></div></td></tr></tbody></table> <figure typeof="mw:File/Thumb"><a href="/wiki/File:Old_RA_diagram.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/3/30/Old_RA_diagram.png/400px-Old_RA_diagram.png" decoding="async" width="400" height="163" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/3/30/Old_RA_diagram.png/600px-Old_RA_diagram.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/3/30/Old_RA_diagram.png/800px-Old_RA_diagram.png 2x" data-file-width="1158" data-file-height="471" /></a><figcaption>How <b>right ascension</b> got its name. Ancient astronomy was very concerned with the rise and set of celestial objects. The <i>ascension</i> was the point on the <a href="/wiki/Celestial_equator" title="Celestial equator">celestial equator</a> (red) which rose or set at the same time as an object (green) on the <a href="/wiki/Celestial_sphere" title="Celestial sphere">celestial sphere</a>. As seen from the equator, both were on a <a href="/wiki/Great_circle" title="Great circle">great circle</a> from pole to pole (left, <i>sphaera recta</i> or right sphere). From almost anywhere else, they were not (center, <i>sphaera obliqua</i> or oblique sphere). At the poles, objects did not rise or set (right, <i>sphaera parallela</i> or parallel sphere). An object's right ascension was its ascension on a right sphere.<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></figcaption></figure> <p>The concept of right ascension has been known at least as far back as <a href="/wiki/Hipparchus" title="Hipparchus">Hipparchus</a> who measured stars in equatorial coordinates in the 2nd century BC. But Hipparchus and his successors made their <a href="/wiki/Star_catalog" class="mw-redirect" title="Star catalog">star catalogs</a> in <a href="/wiki/Ecliptic_coordinate_system" title="Ecliptic coordinate system">ecliptic coordinates</a>, and the use of RA was limited to special cases. </p><p>With the invention of the <a href="/wiki/Telescope" title="Telescope">telescope</a>, it became possible for astronomers to observe celestial objects in greater detail, provided that the telescope could be kept pointed at the object for a period of time. The easiest way to do that is to use an <a href="/wiki/Equatorial_mount" title="Equatorial mount">equatorial mount</a>, which allows the telescope to be aligned with one of its two pivots parallel to the Earth's axis. A motorized clock drive often is used with an equatorial mount to cancel out the <a href="/wiki/Earth%27s_rotation" title="Earth's rotation">Earth's rotation</a>. As the equatorial mount became widely adopted for observation, the equatorial coordinate system, which includes right ascension, was adopted at the same time for simplicity. Equatorial mounts could then be accurately pointed at objects with known right ascension and declination by the use of <a href="/wiki/Setting_circles" title="Setting circles">setting circles</a>. The first star catalog to use right ascension and declination was <a href="/wiki/John_Flamsteed" title="John Flamsteed">John Flamsteed</a>'s <i><a href="/wiki/Historia_Coelestis_Britannica" class="mw-redirect" title="Historia Coelestis Britannica">Historia Coelestis Britannica</a></i> (1712, 1725). </p> <div style="clear:both;" class=""></div> <figure class="mw-halign-center" typeof="mw:File/Thumb"><a href="/wiki/File:Stars_and_ra.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/b/be/Stars_and_ra.png/500px-Stars_and_ra.png" decoding="async" width="500" height="280" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/be/Stars_and_ra.png/750px-Stars_and_ra.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/be/Stars_and_ra.png/1000px-Stars_and_ra.png 2x" data-file-width="1608" data-file-height="900" /></a><figcaption>The entire sky, divided into two halves. <b>Right ascension</b> (blue) begins at the <a href="/wiki/Equinox" title="Equinox">March equinox</a> (at right, at the intersection of the <a href="/wiki/Ecliptic" title="Ecliptic">ecliptic</a> (red) and the <a href="/wiki/Celestial_equator" title="Celestial equator">equator</a> (green)) and increases eastward (towards the left). The lines of right ascension (blue) from pole to pole divide the sky into 24 hours, each equivalent to 15°.</figcaption></figure> <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=Right_ascension&action=edit&section=5" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1184024115">.mw-parser-output .div-col{margin-top:0.3em;column-width:30em}.mw-parser-output .div-col-small{font-size:90%}.mw-parser-output .div-col-rules{column-rule:1px solid #aaa}.mw-parser-output .div-col dl,.mw-parser-output .div-col ol,.mw-parser-output .div-col ul{margin-top:0}.mw-parser-output .div-col li,.mw-parser-output .div-col dd{page-break-inside:avoid;break-inside:avoid-column}</style><div class="div-col" style="column-width: 30em;"> <ul><li><a href="/wiki/Celestial_coordinate_system" class="mw-redirect" title="Celestial coordinate system">Celestial coordinate system</a></li> <li><a href="/wiki/Celestial_pole" title="Celestial pole">Celestial pole</a></li> <li><a href="/wiki/Declination" title="Declination">Declination</a></li> <li><a href="/wiki/Ecliptic" title="Ecliptic">Ecliptic</a></li> <li><a href="/wiki/Equatorial_coordinate_system" title="Equatorial coordinate system">Equatorial coordinate system</a></li> <li><a href="/wiki/Equinoctial_colure" class="mw-redirect" title="Equinoctial colure">Equinoctial colure</a></li> <li><a href="/wiki/Geographic_coordinate_system" title="Geographic coordinate system">Geographic coordinate system</a></li> <li><a href="/wiki/Hour_angle" title="Hour angle">Hour angle</a></li> <li><a href="/wiki/Right_ascension_of_the_ascending_node" class="mw-redirect" title="Right ascension of the ascending node">Right ascension of the ascending node (RAAN)</a></li> <li><a href="/wiki/Setting_circles" title="Setting circles">Setting circles</a></li> <li><a href="/wiki/Sidereal_time" title="Sidereal time">Sidereal time</a></li></ul></div> <div class="mw-heading mw-heading2"><h2 id="Notes_and_references">Notes and references</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Right_ascension&action=edit&section=6" title="Edit section: Notes and 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"><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 id="CITEREFU.S._Naval_Observatory_Nautical_Almanac_Office1992" class="citation book cs1">U.S. Naval Observatory Nautical Almanac Office (1992). Seidelmann, P. Kenneth (ed.). <i>Explanatory Supplement to the Astronomical Almanac</i>. University Science Books, Mill Valley, CA. p. 735. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-935702-68-7" title="Special:BookSources/0-935702-68-7"><bdi>0-935702-68-7</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Explanatory+Supplement+to+the+Astronomical+Almanac&rft.pages=735&rft.pub=University+Science+Books%2C+Mill+Valley%2C+CA&rft.date=1992&rft.isbn=0-935702-68-7&rft.au=U.S.+Naval+Observatory+Nautical+Almanac+Office&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARight+ascension" 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"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBlaeu1668" class="citation book cs1"><a href="/wiki/Willem_Blaeu" title="Willem Blaeu">Blaeu, Guilielmi</a> (1668). <a rel="nofollow" class="external text" href="https://archive.org/details/guilielmiblaeui00hortgoog"><i>Institutio Astronomica</i></a>. Apud Johannem Blaeu. p. 65.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Institutio+Astronomica&rft.pages=65&rft.pub=Apud+Johannem+Blaeu&rft.date=1668&rft.aulast=Blaeu&rft.aufirst=Guilielmi&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Fguilielmiblaeui00hortgoog&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARight+ascension" class="Z3988"></span>, "<i>Ascensio recta</i> Solis, stellæ, aut alterius cujusdam signi, est gradus æquatorus cum quo simul exoritur in sphæra recta"; roughly translated, "<i>Right ascension</i> of the Sun, stars, or any other sign, is the degree of the equator that rises together in a right sphere"</span> </li> <li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLathrop1821" class="citation book cs1">Lathrop, John (1821). <a rel="nofollow" class="external text" href="https://archive.org/details/bub_gb_Z1QmAAAAMAAJ"><i>A Compendious Treatise on the Use of Globes and Maps</i></a>. Wells and Lilly and J.W. Burditt, Boston. pp. <a rel="nofollow" class="external text" href="https://archive.org/details/bub_gb_Z1QmAAAAMAAJ/page/n39">29</a>, 39.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=A+Compendious+Treatise+on+the+Use+of+Globes+and+Maps&rft.pages=29%2C+39&rft.pub=Wells+and+Lilly+and+J.W.+Burditt%2C+Boston&rft.date=1821&rft.aulast=Lathrop&rft.aufirst=John&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Fbub_gb_Z1QmAAAAMAAJ&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARight+ascension" class="Z3988"></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"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFMoulton1916" class="citation book cs1"><a href="/wiki/Forest_Ray_Moulton" title="Forest Ray Moulton">Moulton, Forest Ray</a> (1916). <a rel="nofollow" class="external text" href="https://archive.org/details/anintroductiont06moulgoog"><i>An Introduction to Astronomy</i></a>. Macmillan Co., New York. pp. <a rel="nofollow" class="external text" href="https://archive.org/details/anintroductiont06moulgoog/page/n156">125</a>–126.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=An+Introduction+to+Astronomy&rft.pages=125-126&rft.pub=Macmillan+Co.%2C+New+York&rft.date=1916&rft.aulast=Moulton&rft.aufirst=Forest+Ray&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Fanintroductiont06moulgoog&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARight+ascension" class="Z3988"></span></span> </li> <li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text">Moulton (1916), p. 126.</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"><i>Explanatory Supplement</i> (1992), p. 11.</span> </li> <li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text">Moulton (1916), pp. 92–95.</span> </li> <li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text">see, for instance, <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFU.S._Naval_Observatory_Nautical_Almanac_OfficeU.K._Hydrographic_OfficeH.M._Nautical_Almanac_Office2008" class="citation book cs1">U.S. Naval Observatory Nautical Almanac Office; U.K. Hydrographic Office; H.M. Nautical Almanac Office (2008). "Time Scales and Coordinate Systems, 2010". <i>The Astronomical Almanac for the Year 2010</i>. U.S. Govt. Printing Office. p. B2.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Time+Scales+and+Coordinate+Systems%2C+2010&rft.btitle=The+Astronomical+Almanac+for+the+Year+2010&rft.pages=B2&rft.pub=U.S.+Govt.+Printing+Office&rft.date=2008&rft.au=U.S.+Naval+Observatory+Nautical+Almanac+Office&rft.au=U.K.+Hydrographic+Office&rft.au=H.M.+Nautical+Almanac+Office&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARight+ascension" class="Z3988"></span></span> </li> <li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text">Blaeu (1668), p. 40–41.</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=Right_ascension&action=edit&section=7" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a rel="nofollow" class="external text" href="http://stars.astro.illinois.edu/celsph.html">MEASURING THE SKY A Quick Guide to the Celestial Sphere</a> James B. Kaler, University of Illinois</li> <li><a rel="nofollow" class="external text" href="http://astro.unl.edu/naap/motion1/cec_units.html">Celestial Equatorial Coordinate System</a> University of Nebraska-Lincoln</li> <li><a rel="nofollow" class="external text" href="http://astro.unl.edu/naap/motion1/cec_both.html">Celestial Equatorial Coordinate Explorers</a> University of Nebraska-Lincoln</li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFMerrifield" class="citation web cs1">Merrifield, Michael. <a rel="nofollow" class="external text" href="http://www.sixtysymbols.com/videos/declination.htm">"(α,δ) – Right Ascension & Declination"</a>. <i>Sixty Symbols</i>. <a href="/wiki/Brady_Haran" title="Brady Haran">Brady Haran</a> for the <a href="/wiki/University_of_Nottingham" title="University of Nottingham">University of Nottingham</a>.</cite><span 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