{"id":2985,"date":"2025-03-06T16:46:14","date_gmt":"2025-03-06T15:46:14","guid":{"rendered":"https:\/\/deep-space-astronomy.geekworkers.dev\/produit\/71f-flat-field\/"},"modified":"2026-08-30T14:20:26","modified_gmt":"2026-08-30T12:20:26","slug":"71f-flat-field","status":"publish","type":"product","link":"https:\/\/deep-space-astronomy.ch\/en\/product\/71f-flat-field\/","title":{"rendered":"Askar 71F Flat-Field APO"},"content":{"rendered":"

Askar 71F \u2013 71 mm Apochromatic Flat-Field Eyepiece<\/h2>\n

Visit Askar 71F<\/strong> is a compact and versatile apochromatic telescope, designed for both
\nl\u2019wide-field astrophotography<\/strong> as well as for visual observation. Its air-spaced quadruplet objective,
\nfeaturing an ED glass element, offers excellent chromatic aberration correction and a corrected field compatible with the
\nfull-frame sensors.<\/p>\n

Thanks to its optical design featuring integrated flat field<\/strong>, the 71F does not require any additional field corrector.
\nIt is also not necessary to maintain a specific backfocus distance: simply connect the equipment
\ntake a photo, and then focus.<\/p>\n

Highlights<\/h3>\n
    \n
  • 71 mm aperture<\/li>\n
  • Focal length of 490 mm<\/li>\n
  • Focal ratio of f\/6.9<\/li>\n
  • APO Quadruplet Lens with Air Spacing<\/li>\n
  • An ED glass optical element<\/li>\n
  • 44 mm corrected field of view, full-frame compatible<\/li>\n
  • Integrated field corrector<\/li>\n
  • No precise calculation of the backfocus is required<\/li>\n
  • Suitable for astrophotography and visual observation<\/li>\n
  • 2.4-inch rack-and-pinion eyepiece holder<\/li>\n
  • 1:10 micrometric reduction<\/li>\n
  • 360\u00b0 Graduated Field Rotator<\/li>\n
  • Retractable mist guard<\/li>\n
  • Multiple slots for researchers and accessories<\/li>\n
  • 230 mm Vixen Dovetail<\/li>\n
  • 1\/4\u2033 and 3\/8\u2033 threads for direct attachment to a camera tripod<\/li>\n<\/ul>\n

    A compact, high-performance lens<\/h3>\n

    The Askar 71F has an aperture of 71 mm<\/strong>, a focal length of 490 mm<\/strong> and a native focal ratio
    \nfrom f\/6.9<\/strong>. Its air-spaced APO quadruplet optical design includes an ED element that helps reduce
    \neffectively corrects chromatic aberrations.<\/p>\n

    Its image circle, corrected for 44 mm<\/strong> allows it to be used with astronomical cameras and regular cameras
    \nequipped with full-frame sensors, while maintaining well-defined stars all the way to the corners of the image.<\/p>\n

    Integrated field corrector<\/h3>\n

    The 71F is a native flat-field eyepiece. Therefore, it does not require the purchase of a field corrector or a field flattener.
    \nadditional. Unlike many astronomical telescopes, it also does not require you to maintain a certain distance
    \na fixed backfocus distance between the lens and the sensor.<\/p>\n

    After setting up your camera, filter wheel, or camera, all you need to do is focus to
    \nbegin data acquisition. This design greatly simplifies the setup of the imaging system.<\/p>\n

    Versatile photographic connection<\/h3>\n

    The Askar 71F comes with a set of photographic adapter rings and tubes that include, among other things, connections
    \nM54 \u00d7 0.75<\/strong> and M48 \u00d7 0.75<\/strong>. The M48 adapter also features a thread that allows
    \nthe installation of a 2-inch filter.<\/p>\n

    The eyepiece can therefore be easily used with an SLR or mirrorless camera, a cooled astronomical camera,
    \na filter wheel, a filter drawer, or other photography accessories.<\/p>\n

    Mechanical Engineering<\/h3>\n

    The optical tube is fully CNC-machined and features a compact, rugged design. The retractable anti-fog shield
    \nreduces the transport distance, while its interior, coated with a matte finish, minimizes unwanted reflections.<\/p>\n

    The rack-and-pinion eyepiece holder from 2.4 inches<\/strong> features a multi-stage focusing system 1:10<\/strong>.
    \nA 360\u00b0 graduated field rotator allows for precise adjustment of the camera's orientation.<\/p>\n

    The top handle has a slot for a search tool. There are two additional slots on each side.
    \nfrom the eyepiece holder to mount a finder scope, a guiding system, a mini-computer, or other accessories.<\/p>\n

    Mounting on a bracket or tripod<\/h3>\n

    The telescope is equipped with a Vixen dovetail mount 230 mm<\/strong>. It also has threads
    \n1\/4\u2033<\/strong> and 3\/8\u2033<\/strong>, allowing for direct attachment to many camera tripods or heads
    \ncompatible panoramic images.<\/p>\n

    When using the camera on a tripod, make sure that the head and tripod can comfortably support the
    \nTotal weight of the scope and its accessories.<\/p>\n

    Technical specifications<\/h3>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
    Opening<\/th>\n71 mm<\/td>\n<\/tr>\n
    Focal length<\/th>\n490 mm<\/td>\n<\/tr>\n
    Focus report<\/th>\nf\/6.9<\/td>\n<\/tr>\n
    Optical package<\/th>\nAPO Quadruplet with Air Spacing<\/td>\n<\/tr>\n
    ED glass<\/th>\n1 item<\/td>\n<\/tr>\n
    Image circle<\/th>\n44 mm, full-format compatible<\/td>\n<\/tr>\n
    Field corrector<\/th>\nIntegrated<\/td>\n<\/tr>\n
    Eyepiece Holder Travel<\/th>\n50 mm<\/td>\n<\/tr>\n
    Lens holder<\/th>\n2.4-inch rack, 1:10 two-speed<\/td>\n<\/tr>\n
    Rotator<\/th>\n360\u00b0 Graduated Field Rotator<\/td>\n<\/tr>\n
    Optical tube weight<\/th>\n2.5 kg<\/td>\n<\/tr>\n
    Weight with collars and dovetail<\/th>\n3 kg<\/td>\n<\/tr>\n
    Dovetail<\/th>\nVixen, length 230 mm<\/td>\n<\/tr>\n
    Threads for tripods<\/th>\n1\/4\u2033 and 3\/8\u2033<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    Total length<\/h3>\n\n\n\n\n\n\n\n
    Configuration<\/th>\nLength<\/th>\n<\/tr>\n
    With 1.25\u2033 adapter, dew shield retracted<\/td>\n372.5 mm<\/td>\n<\/tr>\n
    With 1.25-inch adapter, anti-fog screen deployed<\/td>\n430.9 mm<\/td>\n<\/tr>\n
    With camera adapter, anti-fog screen retracted<\/td>\n415 mm<\/td>\n<\/tr>\n
    With camera adapter, anti-fog screen deployed<\/td>\n473.4 mm<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    Rear Connections<\/h3>\n
      \n
    • M64 \u00d7 0.75 to M54 \u00d7 0.75<\/li>\n
    • M54 \u00d7 0.75 to M54 \u00d7 0.75<\/li>\n
    • M54 \u00d7 0.75 to M48 \u00d7 0.75<\/li>\n
    • 2-inch internal filter thread on the M48 adapter<\/li>\n<\/ul>\n

      Available length for accessories<\/h3>\n\n\n\n\n\n\n\n\n
      Configuration<\/th>\nEyepiece holder retracted<\/th>\nEyepiece holder extended<\/th>\n<\/tr>\n<\/thead>\n
      From the M48 \u00d7 0.75 male thread<\/td>\n82.5 mm<\/td>\n32.5 mm<\/td>\n<\/tr>\n
      From the M54 \u00d7 0.75 male thread<\/td>\n100.5 mm<\/td>\n50.5 mm<\/td>\n<\/tr>\n
      From the 1.25-inch eyepiece holder<\/td>\n111 mm<\/td>\n61 mm<\/td>\n<\/tr>\n
      From the 2-inch eyepiece holder<\/td>\n121 mm<\/td>\n71 mm<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

      Scope of delivery<\/h3>\n
        \n
      • Askar 71F optical tube<\/li>\n
      • A pair of mounting clamps<\/li>\n
      • Top handle<\/li>\n
      • 230 mm Vixen Dovetail<\/li>\n
      • Photographic Adapter Set<\/li>\n
      • 1.25-inch Visual Adapter<\/li>\n<\/ul>\n

        Note:<\/strong> cameras, video cameras, filters, elbow mirrors, eyepieces, focusing systems
        \nElectronics and other accessories shown in some illustrations are not necessarily included.<\/p>","protected":false},"excerpt":{"rendered":"

        Askar 71F \u2013 Lunette apochromatique \u00e0 champ plat de 71 mm La Askar 71F est une lunette apochromatique compacte et polyvalente, con\u00e7ue aussi bien pour l\u2019astrophotographie grand champ que pour l\u2019observation visuelle. Son objectif quadruplet \u00e0 espacement d\u2019air, comprenant un \u00e9l\u00e9ment en verre ED, offre une excellente correction chromatique et un champ corrig\u00e9 compatible avec […]<\/p>\n","protected":false},"featured_media":2984,"comment_status":"open","ping_status":"closed","template":"","meta":[],"product_brand":[382],"product_cat":[755,384],"product_tag":[856],"class_list":["post-2985","product","type-product","status-publish","has-post-thumbnail","product_brand-askar","product_cat-lunettes-apochromatiques","product_cat-lunettes_refracteurs","product_tag-produits-phares-en-stock","first","instock","taxable","shipping-taxable","purchasable","product-type-simple"],"_links":{"self":[{"href":"https:\/\/deep-space-astronomy.ch\/en\/wp-json\/wp\/v2\/product\/2985","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/deep-space-astronomy.ch\/en\/wp-json\/wp\/v2\/product"}],"about":[{"href":"https:\/\/deep-space-astronomy.ch\/en\/wp-json\/wp\/v2\/types\/product"}],"replies":[{"embeddable":true,"href":"https:\/\/deep-space-astronomy.ch\/en\/wp-json\/wp\/v2\/comments?post=2985"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/deep-space-astronomy.ch\/en\/wp-json\/wp\/v2\/media\/2984"}],"wp:attachment":[{"href":"https:\/\/deep-space-astronomy.ch\/en\/wp-json\/wp\/v2\/media?parent=2985"}],"wp:term":[{"taxonomy":"product_brand","embeddable":true,"href":"https:\/\/deep-space-astronomy.ch\/en\/wp-json\/wp\/v2\/product_brand?post=2985"},{"taxonomy":"product_cat","embeddable":true,"href":"https:\/\/deep-space-astronomy.ch\/en\/wp-json\/wp\/v2\/product_cat?post=2985"},{"taxonomy":"product_tag","embeddable":true,"href":"https:\/\/deep-space-astronomy.ch\/en\/wp-json\/wp\/v2\/product_tag?post=2985"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}