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  <front>
    <journal-meta>
      <journal-id journal-id-type="ojs">izvcrao</journal-id>
      <journal-id journal-id-type="publisher-id" xml:lang="ru">
                       Изв. Крымск. Астрофиз. Обсерв.
                </journal-id>
      <journal-id journal-id-type="publisher-id" xml:lang="en">
                        Izv. Krymsk. Astrofiz. Observ.
                    </journal-id>
      <journal-title-group>
        <journal-title xml:lang="ru">
                    Известия Крымской астрофизической обсерватории
                </journal-title>
        <trans-title-group xml:lang="en">
          <trans-title>Izvestiya Krymskoi Astrofizicheskoi Observatorii</trans-title>
        </trans-title-group>
      </journal-title-group>
      <issn pub-type="ppub">0367-8466</issn>
      <issn pub-type="epub">3034-4107</issn>
      <publisher>
        <publisher-name>Киселев Н.Н., пос. Московский, Москва, РФ</publisher-name>
        <publisher-loc>RU</publisher-loc>
      </publisher>
      <self-uri xlink:href="https://jncrao.ru/index.php/izvcrao"/>
    </journal-meta>
    <article-meta>
      <article-id pub-id-type="publisher-id">608</article-id>
      <article-categories>
        <subj-group xml:lang="ru" subj-group-type="heading">
          <subject>Научные статьи</subject>
        </subj-group>
        <subj-group xml:lang="en" subj-group-type="heading">
          <subject>Research articles</subject>
        </subj-group>
      </article-categories>
      <title-group>
        <article-title xml:lang="ru">A purely reflective large wide-field telescope</article-title>
      </title-group>
      <contrib-group content-type="author">
        <contrib>
          <name-alternatives>
            <name name-style="western" xml:lang="en" specific-use="">
              <surname>Terebizh</surname>
              <given-names>V.Yu.</given-names>
            </name>
          </name-alternatives>
          <xref ref-type="aff" rid="aff-1"/>
        </contrib>
      </contrib-group>
      <aff id="aff-1">
        <institution content-type="orgname" xml:lang="en">Sternberg Astronomical Institute, Russia; Crimean Astrophysical Observatory, Ukraine</institution>
      </aff>
      <pub-date date-type="pub" iso-8601-date="2008-12-26">
        <day>26</day>
        <month>12</month>
        <year>2008</year>
      </pub-date>
      <volume>104</volume>
      <issue>1</issue>
      <fpage>240</fpage>
      <lpage>248</lpage>
      <history>
        <date date-type="received" iso-8601-date="2018-06-15">
          <day>15</day>
          <month>06</month>
          <year>2018</year>
        </date>
      </history>
      <permissions>
        <copyright-statement xml:lang="ru">Copyright (c) 2008 </copyright-statement>
        <copyright-statement xml:lang="en">Copyright (c) 2008 Terebizh V.</copyright-statement>
        <copyright-year>
					2008
				</copyright-year>
        <copyright-holder xml:lang="ru"/>
        <copyright-holder xml:lang="en">Terebizh V.</copyright-holder>
        <license license-type="open-access" xlink:href="http://creativecommons.org/licenses/by/4.0" xml:lang="ru">
          <license-p> Метаданные этой статьи доступны по лицензии  Creative Commons «Attribution» («Атрибуция») 4.0 Всемирная.  
 Авторское право и право на публикацию текстов, представленных в журнале  "Известия Крымской астрофизической обсерватории", сохраняются за авторами, при этом право первой публикации предоставляется журналу. Тексты могут свободно использоваться при условии правильного цитирования с указанием авторства в соответствии с лицензией  Creative Commons «Attribution» («Атрибуция») 4.0 Всемирная.  
     </license-p>
        </license>
        <license license-type="open-access" xlink:href="http://creativecommons.org/licenses/by/4.0" xml:lang="en">
          <license-p> The metadata for this submission is licensed under a  Creative Commons Attribution 4.0 International License.  
 Copyright and publishing rights for texts published in Izvestiya Krymskoi Astrofizicheskoi Observatorii is retained by the authors, with first publication rights granted to the journal.Texts are free to use with proper attribution and link to the licensing  (Creative Commons Attribution 4.0 International).  
     </license-p>
        </license>
      </permissions>
      <self-uri xlink:href="https://jncrao.ru/index.php/izvcrao/article/view/608"/>
      <abstract xml:lang="ru">
        <p> Two versions of a fast, purely reflective Paul-Baker type telescope are discussed, each with an 8.4-m aperture, 3° diameter flat field and f/1.25 focal ratio. 
 The first version is based on a common, even asphere type of surface with zero conic constant. The primary and tertiary mirrors are 6th order aspheres, while the secondary mirror is an 8th order asphere (referred to here for brevity, as the 6/8/6 configuration). The D 80  diameter of a star image varies from 0′′.18 on the optical axis up to 0′′ .27 at the edge of the field (9.3 – 13.5μm). 
 The second version of the telescope is based on a polysag surface type which uses a polynomial expansion in the sag&amp;nbsp;z, 
  r  2  = 2 R  0  z  – (1 + b) z  2  + a 3  z  3  + a 4  z  4  + … + a  N z N  , 
 instead of the common form of an aspheric surface. This approach results in somewhat better images, with D 80  ranging from 0′′.16 to 0′′.23, using a lower-order 3/4/3 combination of powers for the mirror surfaces. 
 An additional example with 3.5-m aperture, 3 ∘ .5 diameter flat field, and f/1.25 focal ratio featuring near-diffraction-limited image quality is also presented. </p>
      </abstract>
      <counts>
        <page-count count="9"/>
      </counts>
    </article-meta>
  </front>
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