{"id":14966,"date":"2026-05-08T16:50:05","date_gmt":"2026-05-08T14:50:05","guid":{"rendered":"https:\/\/deep-space-astronomy.ch\/?post_type=product&p=14966"},"modified":"2026-05-08T17:16:24","modified_gmt":"2026-05-08T15:16:24","slug":"askar-91f","status":"publish","type":"product","link":"https:\/\/deep-space-astronomy.ch\/en\/product\/askar-91f\/","title":{"rendered":"Askar 91F"},"content":{"rendered":"

Askar 91F Flat-Field - APO Quadruplet Premium scope for Full Frame Astrophotography and Observation<\/h2>\n

L'Askar 91F Flat-Field<\/strong> is a top-of-the-range apochromatic refractor designed for astronomers looking for a versatile instrument capable of excelling in both astrophotography and visual observation. With its 91 mm<\/strong>, its focal length of 609 mm<\/strong> and its native focal ratio of f\/6.7<\/strong>, It offers an excellent compromise between power, optical quality and transportability.<\/p>\n

Thanks to its optical formula self-correcting APO quadruplet<\/strong>, With its ED glass element, the Askar 91F delivers extremely clean, star-fine images even on Full Frame sensors. Its built-in field corrector considerably simplifies astrophotography, eliminating the need for an external flattener and complex backfocus calculations.<\/p>\n

A Full Frame astrographic telescope ready for use<\/h3>\n

The Askar 91F has been designed to offer a fluid and efficient user experience. Unlike many glasses that require an external corrector, this version directly integrates a correction system optimized for an image circle of 44 mm<\/strong>, perfectly compatible with full-format sensors.<\/p>\n

Simply connect your camera via the supplied adapters, focus and start acquiring data without having to deal with complex spacing.<\/p>\n

This approach not only reduces hidden costs, but also improves mechanical reliability and setup simplicity.<\/p>\n

High-performance quadruplet APO optical design<\/h3>\n

Askar 91F is based on a four-lens spaced-apart optical formula comprising :<\/p>\n

    \n
  • Three front elements<\/li>\n
  • A rear corrective lens<\/li>\n
  • An ED glass element<\/li>\n<\/ul>\n

    This configuration is highly effective in reducing chromatic aberration, while maintaining excellent sharpness across the entire field.<\/p>\n

    With its 609 mm focal length, the Askar 91F is particularly suitable for :<\/p>\n

      \n
    • Medium-sized nebulae<\/li>\n
    • Extended galaxies<\/li>\n
    • Globular clusters<\/li>\n
    • Large deep-sky objects<\/li>\n
    • Wide-field astrophotography in detail<\/li>\n<\/ul>\n

      Astrophotography, terrestrial observation and photography<\/h3>\n

      One of the great advantages of the Askar 91F is its versatility. This scope can be used for :<\/p>\n

        \n
      • Deep-sky astrophotography<\/li>\n
      • Astronomical observation<\/li>\n
      • Ground observation<\/li>\n
      • Birdwatching<\/li>\n
      • Nature photography<\/li>\n<\/ul>\n

        For this reason, Askar directly supplies several visual accessories:<\/p>\n

          \n
        • 8 mm eyepiece<\/li>\n
        • 20 mm eyepiece<\/li>\n
        • 1.25\u201d 45\u00b0 rectifying prism<\/li>\n<\/ul>\n

          The 20 mm eyepiece offers a magnification of approx. 30x, while the 8 mm reaches approx. 76x, enabling observation of landscapes as well as lunar details.<\/p>\n

          The rectifying prism provides a correctly oriented image, highly appreciated for terrestrial observation.<\/p>\n

          Robust mechanics and premium finish<\/h3>\n

          The Askar 91F boasts a particularly meticulous mechanical construction, high-quality CNC finishing and an elegant blue-and-white design.<\/p>\n

          The retractable mist shield enhances portability, while the inside of the tube is lined with an absorbent material that effectively limits stray reflections.<\/p>\n

          The tube also incorporates :<\/p>\n

            \n
          • Sturdy 130 mm handle<\/li>\n
          • Several researcher supports<\/li>\n
          • Accessory slots<\/li>\n
          • 230 mm Vixen dovetail<\/li>\n<\/ul>\n

            Integrated 1\/4\u201d and 3\/8\u201d threads allow direct attachment to photo tripods.<\/p>\n

            High-rigidity 3-inch Rack & Pinion eyepiece holder<\/h3>\n

            The focusing system is based on an imposing eyepiece holder 3-inch Rack & Pinion<\/strong>, designed to support advanced imaging setups without bending.<\/p>\n

            This focuser includes :<\/p>\n

              \n
            • Fine 1:10 gear ratio<\/li>\n
            • 360\u00b0 graduated rotation<\/li>\n
            • Excellent mechanical rigidity<\/li>\n
            • Compatible with electronic focus motors<\/li>\n<\/ul>\n

              This design ensures precise, stable focusing even with heavy cameras and complex optical trains.<\/p>\n

              Extended compatibility with accessories<\/h3>\n

              The Askar 91F is supplied with several adapters for easy integration with the majority of equipment on the market.<\/p>\n

              These include :<\/p>\n

                \n
              • M54x0.75<\/li>\n
              • M48x0.75<\/li>\n
              • Integrated 2-inch filter thread<\/li>\n
              • 1.25\u201d and 2\u201d adapters\u201d<\/li>\n<\/ul>\n

                This extended compatibility facilitates use with :<\/p>\n

                  \n
                • Astronomical CMOS cameras<\/li>\n
                • DSLR<\/li>\n
                • Hybrid cameras<\/li>\n
                • Standard visual accessories<\/li>\n<\/ul>\n

                  Summary table of technical specifications<\/h3>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
                  Features<\/th>\nValue<\/th>\n<\/tr>\n
                  Optical type<\/td>\nQuadruplet APO air-spaced with ED glass<\/td>\n<\/tr>\n
                  Opening<\/td>\n91 mm<\/td>\n<\/tr>\n
                  Focal length<\/td>\n609 mm<\/td>\n<\/tr>\n
                  Focus report<\/td>\nf\/6.7<\/td>\n<\/tr>\n
                  Image circle<\/td>\n44 mm Full Frame<\/td>\n<\/tr>\n
                  Field corrector<\/td>\nIntegrated<\/td>\n<\/tr>\n
                  Lens holder<\/td>\n3\u2033 Rack & Pinion double speed<\/td>\n<\/tr>\n
                  Gearbox<\/td>\n1:10<\/td>\n<\/tr>\n
                  Rotation<\/td>\n360\u00b0 graduated<\/td>\n<\/tr>\n
                  Focuser stroke<\/td>\n30 mm<\/td>\n<\/tr>\n
                  Minimum length<\/td>\n513 mm<\/td>\n<\/tr>\n
                  Maximum length<\/td>\n636 mm<\/td>\n<\/tr>\n
                  Net weight<\/td>\n3.92 kg<\/td>\n<\/tr>\n
                  Weight with collars and dovetail<\/td>\n4.52 kg<\/td>\n<\/tr>\n
                  Rear threads<\/td>\nM64, M54, M48<\/td>\n<\/tr>\n
                  Sensor compatibility<\/td>\nUp to Full Frame<\/td>\n<\/tr>\n
                  Dovetail<\/td>\nVixen 230 mm<\/td>\n<\/tr>\n
                  Accessories included<\/td>\n8 mm and 20 mm eyepieces, 45\u00b0 rectifying prism, photo adapters<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

                  Why choose Askar 91F?<\/h3>\n

                  The Askar 91F is a particularly interesting telescope for astronomers looking for an instrument capable of excelling in several fields without major compromise.<\/p>\n

                  Its modern optical formula, integrated corrector, Full Frame compatibility and robust mechanics make it an ideal platform for both advanced astrophotography and visual or terrestrial observation.<\/p>\n

                  Compact, elegant and extremely versatile, Askar 91F is a premium solution for enthusiasts looking for a high-performance, easy-to-use scope.<\/p>","protected":false},"excerpt":{"rendered":"

                  Askar 91F Flat-Field \u2013 Lunette APO Quadruplet Premium pour Astrophotographie Full Frame et Observation L\u2019Askar 91F Flat-Field est une lunette apochromatique haut de gamme con\u00e7ue pour les astronomes recherchant un instrument polyvalent capable d\u2019exceller aussi bien en astrophotographie qu\u2019en observation visuelle. Avec son ouverture de 91 mm, sa focale de 609 mm et son rapport […]<\/p>\n","protected":false},"featured_media":14968,"comment_status":"open","ping_status":"closed","template":"","meta":[],"product_brand":[382],"product_cat":[755],"product_tag":[],"class_list":{"0":"post-14966","1":"product","2":"type-product","3":"status-publish","4":"has-post-thumbnail","6":"product_brand-askar","7":"product_cat-lunettes-apochromatiques","9":"first","10":"on_supplier","11":"taxable","12":"shipping-taxable","13":"purchasable","14":"product-type-simple"},"_links":{"self":[{"href":"https:\/\/deep-space-astronomy.ch\/en\/wp-json\/wp\/v2\/product\/14966","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=14966"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/deep-space-astronomy.ch\/en\/wp-json\/wp\/v2\/media\/14968"}],"wp:attachment":[{"href":"https:\/\/deep-space-astronomy.ch\/en\/wp-json\/wp\/v2\/media?parent=14966"}],"wp:term":[{"taxonomy":"product_brand","embeddable":true,"href":"https:\/\/deep-space-astronomy.ch\/en\/wp-json\/wp\/v2\/product_brand?post=14966"},{"taxonomy":"product_cat","embeddable":true,"href":"https:\/\/deep-space-astronomy.ch\/en\/wp-json\/wp\/v2\/product_cat?post=14966"},{"taxonomy":"product_tag","embeddable":true,"href":"https:\/\/deep-space-astronomy.ch\/en\/wp-json\/wp\/v2\/product_tag?post=14966"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}