{"product_id":"askar-91f-91mm-f-6-7-quadruplet-flat-field-apo-refractor-91f-pre-owned-1","title":"Askar 91F - 91mm f\/6.7 Quadruplet Flat-Field APO Refractor - 91F (Pre-owned)","description":"\u003cp\u003e\u003cspan style=\"color: rgb(248, 13, 13);\"\u003e\u003cstrong\u003eUsed, in excellent condition\u003c\/strong\u003e\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003cdiv class=\"card__header\"\u003e\n\u003ch3 class=\"card__title heading h3\" style=\"text-align: center;\"\u003eAskar 91 mm Quad ED APO Flat-Field Refractor\u003c\/h3\u003e\n\u003cdiv class=\"card__title heading h3\"\u003e\u003cbr\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"card__section\"\u003e\n\u003cdiv class=\"rte text--pull\"\u003e\n\u003cdiv id=\"saf-detail-0\" class=\"cbox-15 p_loopItem\"\u003e\n\u003cdiv class=\"e_richText-17 s_title clearfix\"\u003e\n\u003cdiv id=\"ce_detail-289423\" data-layout=\"flow\" class=\"ce_detail\"\u003e\n\u003cdiv id=\"ie_grid-1707113026075\" class=\"ie_grid\"\u003e\n\u003cdiv class=\"ie_grid signal\"\u003e\n\u003cdiv class=\"e_box e_box-000 p_gridbox\"\u003e\n\u003cdiv id=\"content_ie-1707113026075-0\" class=\"e_box e_box-000 d_gridCell_0 p_gridCell\"\u003e\n\u003cdiv id=\"ie_grid-1707113026080\" class=\"ie_grid\"\u003e\n\u003cdiv class=\"ie_grid signal\"\u003e\n\u003cdiv class=\"e_box e_box-000 p_gridbox\"\u003e\n\u003cdiv id=\"content_ie-1707113026080-0\" class=\"e_box e_box-000 d_gridCell_0 p_gridCell\"\u003e\n\u003cdiv id=\"ie_fimg-1707113026085\" class=\"ie_fimg\"\u003e\n\u003cdiv style=\"text-align: center;\"\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0851\/2766\/files\/91F_Leading_Banner.jpg?v=1755206667\" alt=\"\"\u003e\u003c\/div\u003e\n\u003ch3 style=\"text-align: center;\"\u003eAskar 71F Flat Field Quad Refractor Highlights\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv id=\"ie_grid-1707113026090\" class=\"ie_grid\"\u003e\n\u003cdiv class=\"ie_grid\"\u003e\n\u003cdiv class=\"e_box e_box-000 p_gridbox\"\u003e\n\u003cdiv id=\"content_ie-1707113026090-0\" class=\"e_box e_box-000 d_gridCell_0 p_gridCell\"\u003e\n\u003cdiv id=\"ie_grid-1707113026095\" class=\"ie_grid\"\u003e\n\u003cdiv class=\"ie_grid\"\u003e\n\u003cdiv class=\"e_box e_box-000 p_gridbox\"\u003e\n\u003cdiv id=\"content_ie-1707113026095-0\" class=\"e_box e_box-000 d_gridCell_0 p_gridCell\"\u003e\n\u003cdiv id=\"ie_grid-1707113026100\" class=\"ie_grid\"\u003e\n\u003cdiv class=\"ie_grid signal\"\u003e\n\u003cdiv class=\"e_box e_box-000 p_gridbox\"\u003e\n\u003cdiv id=\"content_ie-1707113026100-0\" class=\"e_box e_box-000 d_gridCell_0 p_gridCell\"\u003e\n\u003cdiv id=\"ie_text-1707113026110\" class=\"reset_style\"\u003e\n\u003cdiv\u003e\n\u003cp\u003e\u003cspan\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0851\/2766\/files\/91F_Icon_Highlights.png?v=1755206665\" alt=\"\" style=\"display: block; margin-left: auto; margin-right: auto;\"\u003e\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv id=\"ie_line-1707113026330\" class=\"ie_line\"\u003e\u003cspan\u003eThe Askar 91F adopts a quadruplet air-spaced APO lens design, including one piece of ED glass, which can effectively reduce chromatic aberration. The Askar 91F supports 44mm full-frame imaging with great performance of the surrounding star points.\u003c\/span\u003e\u003c\/div\u003e\n\u003cdiv id=\"ie_text-1707113026335\" class=\"reset_style\"\u003e\n\u003cp\u003e\u003cspan\u003eThe Askar 91F is a self-flattened design that allows users to avoid calculating the back focus and buying additional flattener, after attaching the imaging accessories, users can directly use it for shooting after the OTA is in focus. This further reduces the cost and improves the pleasure of shooting.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv id=\"ie_fimg-1707113026340\" class=\"ie_fimg\" style=\"text-align: center;\"\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0851\/2766\/files\/91F_Visual_on_Optional_Tripod.jpg?v=1755206668\" alt=\"\"\u003e\u003c\/div\u003e\n\u003cdiv id=\"ie_text-1707197718594\" class=\"reset_style\"\u003e\n\u003cp\u003e\u003cspan\u003eWith practicality and versatility in mind, the Askar 91F's weight and size are effectively controlled, making it easy to carry and use. The Askar 91F OTA weighs only 3.92kg, with a gross weight of 4.52kg (including the tube rings and dovetail plate).\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cspan\u003eThe Askar 91F is versatile in its use, allowing for both visual observation and astrophotography. For users' convenience, we've also included three observation accessories standard for the 91F: an 8mm eyepiece, a 20mm eyepiece, and a 1.25-inch 45° erecting prism.\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cspan\u003eThe 8mm eyepiece has a magnification of 76x and the 20mm eyepiece has a magnification of 30x. The Askar 91F can be used with different eyepieces depending on the target, and both eyepieces are ideal for viewing birds and landscapes.  \u003c\/span\u003e\u003cspan\u003eBoth eyepieces have a 1.25-inch barrel and a rubberized top for a soft and comfortable user experience.\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cspan\u003eThe 1.25-inch 45° erecting prism provides correct left-to-right and down-to-up image views, making users easy for you to observing without the hassle of seeing images reversed up, down, left, and right.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv id=\"ie_text-1707113026345\" class=\"reset_style\"\u003e\u003c\/div\u003e\n\u003cdiv id=\"ie_fimg-1707113026360\" class=\"ie_fimg\"\u003e\n\u003cmeta charset=\"UTF-8\"\u003e \u003cspan\u003eThe Askar 91F also comes standard with a photographic extension tube with a built-in 2-inch filter thread for easy shooting connections, providing M48×0.75 \u0026amp; M54×0.75 adapters to accommodate various DSLR cameras and professional astronomical cameras, meeting diverse imaging needs.  \u003c\/span\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"ie_fimg\"\u003e\n\u003cspan\u003e\u003c\/span\u003e\u003cbr\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"ie_fimg\" style=\"text-align: center;\"\u003e\u003cspan\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0851\/2766\/files\/91F_Side_Left.png?v=1755206664\" alt=\"\"\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cdiv class=\"ie_fimg\"\u003e\n\u003cdiv class=\"ie_fimg\" id=\"ie_fimg-1749608478311\"\u003e\n\u003cdiv\u003e\u003cspan\u003eThe Askar 91F is an OTA with an aperture of 91mm, a focal length of 609mm, and a native focal ratio of F6.7.  \u003c\/span\u003e\u003c\/div\u003e\n\u003cdiv\u003e\n\u003cspan\u003e\u003c\/span\u003e\u003cbr\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"ie_grid\" id=\"ie_grid-1749608478316\"\u003e\n\u003cdiv class=\"ie_grid signal\"\u003e\n\u003cdiv class=\"e_box e_box-000 p_gridbox\"\u003e\n\u003cdiv class=\"e_box e_box-000 d_gridCell_0 p_gridCell\" id=\"content_ie-1749608478316-0\"\u003e\n\u003cdiv class=\"ie_grid\" id=\"ie_grid-1749608478321\"\u003e\n\u003cdiv class=\"ie_grid\"\u003e\n\u003cdiv class=\"e_box e_box-000 p_gridbox\"\u003e\n\u003cdiv class=\"e_box e_box-000 d_gridCell_0 p_gridCell\" id=\"content_ie-1749608478321-0\"\u003e\n\u003cdiv class=\"ie_grid\" id=\"ie_grid-1749608478326\"\u003e\n\u003cdiv class=\"ie_grid\"\u003e\n\u003cdiv class=\"e_box e_box-000 p_gridbox\"\u003e\n\u003cdiv class=\"e_box e_box-000 d_gridCell_0 p_gridCell\" id=\"content_ie-1749608478326-0\"\u003e\n\u003cdiv class=\"ie_grid\" id=\"ie_grid-1749608478331\"\u003e\n\u003cdiv class=\"ie_grid signal\"\u003e\n\u003cdiv class=\"e_box e_box-000 p_gridbox\"\u003e\n\u003cdiv class=\"e_box e_box-000 d_gridCell_0 p_gridCell\" id=\"content_ie-1749608478331-0\"\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"reset_style\" id=\"ie_text-1749608478566\"\u003e\n\u003cdiv\u003e\n\u003cp\u003e\u003cspan\u003eThe optical design of the Askar 91F features a four-element configuration (three elements in the front and one in the rear), including one piece of ED glass, which can effectively reduce chromatic aberration.The Askar 91F supports 44mm full-frame imaging with great performance of the surrounding star points.\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cspan\u003eThe Askar 91F is a self-flattened design that allows users to avoid calculating the back focus and buying additional flatteners. After attaching the imaging accessories, users can directly use it for shooting after the OTA is in focus. This further reduces the cost and improves the pleasure of shooting.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"ie_fimg\" id=\"ie_fimg-1749608478581\"\u003e\n\u003cdiv\u003e\u003cimg src=\"https:\/\/omo-oss-image.thefastimg.com\/common\/design\/detail\/0478d269-2b76-4a57-9b70-789f95bf93ad.jpg\" width=\"100%\" height=\"100%\" alt=\"长友气体\"\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"ie_fimg\" id=\"ie_fimg-1749608478591\"\u003e\n\u003cdiv\u003e\u003cimg src=\"https:\/\/omo-oss-image.thefastimg.com\/common\/design\/detail\/b8f20973-5d5c-4493-975a-e06d05b020df.jpg\" width=\"100%\" height=\"100%\" alt=\"长友气体\"\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"reset_style\" id=\"ie_text-1749608478601\"\u003e\u003c\/div\u003e\n\u003cdiv class=\"reset_style\" id=\"ie_text-1749608478611\"\u003e\n\u003cdiv\u003e\u003cbr\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv id=\"saf-detail-1\" class=\"cbox-15 p_loopItem\"\u003e\n\u003cdiv class=\"e_richText-17 s_title clearfix response-transition\"\u003e\n\u003cp\u003e\u003cspan\u003eThe Askar 91F features a retractable dew shield, further reducing overall length and enhancing portability.The inside of the tube is pasted with matting felt to better eliminate stray light, while the exterior sports a sleek blue-and-white color scheme with high-quality CNC machining and paint finish.\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cspan\u003eThe Askar 91F’s handle is 130mm long and has a finder base slot. Besides, there are two finder bases on both sides of the focuser, which not only eliminates the need for disassembling when changing the position of the finder scope but also provides additional mounting positions for other astronomical accessories.\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cspan\u003eIn terms of the focuser, the Askar 91F is equipped with a dual-speed R\u0026amp;P 3-inch rigid focuser, which has a 1:10 fine adjustment and a 360° scaled rotator at the rear end for precise angle adjustment. The 230mm Vixen-style dovetail plate includes 1\/4\" and 3\/8\" screw holes for direct tripod mounting.  \u003c\/span\u003e\u003c\/p\u003e\n\u003cp style=\"text-align: center;\"\u003e\u003cspan\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0851\/2766\/files\/91F_Finder_Focus_Knob_Dovetail.jpg?v=1755206665\" alt=\"\"\u003e\u003c\/span\u003e\u003c\/p\u003e\n\u003cp style=\"text-align: center;\"\u003e\u003cspan\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0851\/2766\/files\/91F_Image_Highlights.jpg?v=1755206666\" alt=\"\"\u003e\u003c\/span\u003e\u003c\/p\u003e\n\u003cfigure class=\"table\"\u003e\n\u003ctable class=\"ck-table-resized\"\u003e\n\u003ccolgroup\u003e \u003ccol\u003e \u003ccol\u003e \u003ccol\u003e \u003c\/colgroup\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"3\"\u003eParameters\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAperture size\u003c\/td\u003e\n\u003ctd colspan=\"2\"\u003e91mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFocal length\u003c\/td\u003e\n\u003ctd colspan=\"2\"\u003e609mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFocal ratio\u003c\/td\u003e\n\u003ctd colspan=\"2\"\u003ef\/6.7\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eObjective lens\u003c\/td\u003e\n\u003ctd colspan=\"2\"\u003eQuadruplet air-spaced APO(including one ED glass)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eImage circle\u003c\/td\u003e\n\u003ctd colspan=\"2\"\u003e44mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMaximum accessory connection (with the focuser fully retreated)\u003c\/td\u003e\n\u003ctd\u003eImaging mode:   \u003cbr\u003e75mm (from the base of M48×0.75 male thread）   \u003cbr\u003e93mm（from the base of M54×0.75 male thread)\u003c\/td\u003e\n\u003ctd\u003eObserving mode:   \u003cbr\u003e112mm（from the end of 1.25\" eyepiece holder）   \u003cbr\u003e122mm（from the end of 2\" eyepiece holder）\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTotal length\u003c\/td\u003e\n\u003ctd colspan=\"2\"\u003e513mm(including 1.25\" adapter as dew shield contracted）   \u003cbr\u003e599mm(including 1.25\" adapter as dew shield fully stretched）   \u003cbr\u003e550mm(including the photographic adapter as dew shield contracted）   \u003cbr\u003e636mm(including the photographic adapter as dew shield fully stretched）\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eNet weight\u003c\/td\u003e\n\u003ctd colspan=\"2\"\u003e3.92kg\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eGross weight (Including tube ring\u0026amp;dovetail plate)\u003c\/td\u003e\n\u003ctd colspan=\"2\"\u003e4.52kg\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eRear-end thread type\u003c\/td\u003e\n\u003ctd colspan=\"2\"\u003eM64×1-M54×0.75    \u003cbr\u003eM54×0.75-M54×0.75    \u003cbr\u003eM54×0.75-M48×0.75  (with M48×0.75 filter thread)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eStandard package items\u003c\/td\u003e\n\u003ctd colspan=\"2\"\u003e A 91F OTA，a pair of tube rings, a handle, a 230mm Vixen dovetail plate,a set of photographic adapters, a 1.25-inch erecting prism, an 8mm eyepiece, a 20mm eyepiece\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/figure\u003e\n\u003cp style=\"text-align: center;\"\u003e \u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e","brand":"Askar","offers":[{"title":"Default Title","offer_id":43261106159729,"sku":"USED052207","price":901.55,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0851\/2766\/files\/20260416_143715_1.jpg?v=1779484121","url":"https:\/\/khanscope.com\/fr\/products\/askar-91f-91mm-f-6-7-quadruplet-flat-field-apo-refractor-91f-pre-owned-1","provider":"Khan Scope Centre","version":"1.0","type":"link"}