{"product_id":"ask-91f","title":"Askar 91F Flat-Field Refractor (91F)","description":"\u003ch1 class=\"e_text-8 s_title response-transition\"\u003eAskar 91F Flat-Field Refractor (91F)\u003c\/h1\u003e\n\u003cp class=\"e_text-8 s_title response-transition\"\u003eSelf-flattened quadruplet Astrograph which can be used for visual observing and astrophotography. \u003c\/p\u003e\n\u003cdiv style=\"text-align: start;\"\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0652\/6245\/2965\/files\/a3df0069-a893-4f9b-b959-77540ba5aeb6_1024x1024.jpg?v=1755195570\" alt=\"\" style=\"float: none;\"\u003e\u003c\/div\u003e\n\u003cp\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\/p\u003e\n\u003cdiv style=\"text-align: start;\"\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0652\/6245\/2965\/files\/A_9a55ec00-0c9e-45c6-8a68-0c72daad9299_1024x1024.png?v=1755195912\" style=\"margin-bottom: 16px; float: none;\"\u003e\u003c\/div\u003e\n\u003cp class=\"e_text-8 s_title response-transition\"\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\/p\u003e\n\u003cp class=\"e_text-8 s_title response-transition\"\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\/p\u003e\n\u003cdiv style=\"text-align: start;\"\u003e\u003cimg style=\"float: none;\" alt=\"\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0652\/6245\/2965\/files\/0478d269-2b76-4a57-9b70-789f95bf93ad_1024x1024.jpg?v=1755196015\"\u003e\u003c\/div\u003e\n\u003cdiv style=\"text-align: start;\"\u003e\u003cimg style=\"float: none;\" alt=\"\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0652\/6245\/2965\/files\/b8f20973-5d5c-4493-975a-e06d05b020df_1024x1024.jpg?v=1755196039\"\u003e\u003c\/div\u003e\n\u003cp\u003eThe Askar 91F strikes a balance between practicality and versatility while achieving lightweight portability through its compact design.The OTA weighs just 3.92kg, with a gross weight of 4.52kg (including the tube rings and dovetail plate).  \u003c\/p\u003e\n\u003cp\u003eThe Askar 91F is versatile in its use, allowing for both visual observation and astrophotography.     For user convenience, it comes standard with three visual accessories: an 8mm eyepiece, a 20mm eyepiece, and a 1.25-inch erecting prism.\u003c\/p\u003e\n\u003cdiv style=\"text-align: start;\"\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0652\/6245\/2965\/files\/3abcc63f-9690-4a70-ae61-dcdaec24c590_1024x1024.jpg?v=1755196100\" alt=\"\" style=\"float: none;\"\u003e\u003c\/div\u003e\n\u003cp class=\"e_text-8 s_title response-transition\"\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\/p\u003e\n\u003cdiv style=\"text-align: start;\"\u003e\u003cimg style=\"float: none;\" alt=\"\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0652\/6245\/2965\/files\/d60045b0-2ff2-4e43-9fbe-8740e10fd73e_1024x1024.jpg?v=1755196146\"\u003e\u003c\/div\u003e\n\u003cp\u003eBoth eyepieces are 1.25 inches and have a soft rubberized top for comfortable use.  \u003c\/p\u003e\n\u003cp\u003eThe 1.25-inch erecting prism provides correct left-to-right and down-to-up image views, making users easy for you to conduct terrestrial and astronomical observations without the hassle of seeing images reversed up, down, left, and right.\u003c\/p\u003e\n\u003cdiv style=\"text-align: start;\"\u003e\u003cimg style=\"float: none;\" alt=\"\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0652\/6245\/2965\/files\/b036cb1a-693f-4a79-88ad-0ec7247137c2_1024x1024.jpg?v=1755196245\"\u003e\u003c\/div\u003e\n\u003cp class=\"e_text-8 s_title response-transition\"\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\/p\u003e\n\u003cp\u003eThe mechanical design of the Askar 91F itself adheres to Askar's consistent philosophy of taking into account the user's habits and minimizing the user's invisible costs.\u003c\/p\u003e\n\u003cp class=\"e_text-8 s_title response-transition\"\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\/p\u003e\n\u003cp class=\"e_text-8 s_title response-transition\"\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\/p\u003e\n\u003cp class=\"e_text-8 s_title response-transition\"\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\/p\u003e\n\u003cdiv style=\"text-align: start;\"\u003e\u003cimg style=\"margin-bottom: 16px; float: none;\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0652\/6245\/2965\/files\/45be5f3f-49d0-47af-9dd9-e3be0d6c9057_1024x1024.jpg?v=1755196372\"\u003e\u003c\/div\u003e\n\u003cp\u003eThe rear interface of the Askar 91F includes both 2-inch and 1.25-inch adapters, enabling compatibility with a wide range of astronomical accessories.  \u003c\/p\u003e\n\u003cp\u003eWhether for deep-sky astrophotography, planetary observation, or birdwatching and travel, the 91F is your ideal companion for exploring the world.\u003c\/p\u003e\n\u003cdiv style=\"text-align: start;\"\u003e\u003cimg style=\"float: none;\" alt=\"\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0652\/6245\/2965\/files\/4e1e8fa8-f15f-4591-a1ca-c2906621e6a5_1024x1024.jpg?v=1755196411\"\u003e\u003c\/div\u003e\n\u003ch3\u003eTechnical Specifications \u003c\/h3\u003e\n\u003ctable class=\"ck-table-resized\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd style=\"text-align: center;\"\u003eAperture size\u003c\/td\u003e\n\u003ctd colspan=\"2\" style=\"text-align: center;\"\u003e91mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"text-align: center;\"\u003eFocal length\u003c\/td\u003e\n\u003ctd colspan=\"2\" style=\"text-align: center;\"\u003e609mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"text-align: center;\"\u003eFocal ratio\u003c\/td\u003e\n\u003ctd colspan=\"2\" style=\"text-align: center;\"\u003ef\/6.7\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"text-align: center;\"\u003eObjective lens\u003c\/td\u003e\n\u003ctd colspan=\"2\" style=\"text-align: center;\"\u003eQuadruplet air-spaced APO(including one ED glass)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"text-align: center;\"\u003eImage circle\u003c\/td\u003e\n\u003ctd colspan=\"2\" style=\"text-align: center;\"\u003e44mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"text-align: center;\"\u003eMaximum accessory connection (with the focuser fully retreated)\u003c\/td\u003e\n\u003ctd style=\"text-align: center;\"\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 style=\"text-align: center;\"\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 style=\"text-align: center;\"\u003eTotal length\u003c\/td\u003e\n\u003ctd colspan=\"2\" style=\"text-align: center;\"\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 style=\"text-align: center;\"\u003eNet weight\u003c\/td\u003e\n\u003ctd colspan=\"2\" style=\"text-align: center;\"\u003e3.92kg\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"text-align: center;\"\u003eGross weight (Including tube ring\u0026amp;dovetail plate)\u003c\/td\u003e\n\u003ctd colspan=\"2\" style=\"text-align: center;\"\u003e4.52kg\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"text-align: center;\"\u003eRear-end thread type\u003c\/td\u003e\n\u003ctd colspan=\"2\" style=\"text-align: center;\"\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 style=\"text-align: center;\"\u003eStandard package items\u003c\/td\u003e\n\u003ctd colspan=\"2\" style=\"text-align: center;\"\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\u003cp\u003e \u003c\/p\u003e\n\u003ch2\u003eProduct Size Diagram\u003c\/h2\u003e\n\u003cdiv style=\"text-align: start;\"\u003e\u003cimg style=\"float: none;\" alt=\"\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0652\/6245\/2965\/files\/1eb9821b-8afc-4233-854d-913f60c86dbc_1024x1024.jpg?v=1755196473\"\u003e\u003c\/div\u003e\n\u003ch2\u003eConnection Diagram\u003c\/h2\u003e\n\u003cdiv style=\"text-align: start;\"\u003e\u003cimg style=\"float: none;\" alt=\"\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0652\/6245\/2965\/files\/1f5f8ab1-9559-4f86-bb0a-41ab7be8b2e4_1024x1024.jpg?v=1755196582\"\u003e\u003c\/div\u003e\n\u003ch2\u003eEAF Connection\u003c\/h2\u003e\n\u003cdiv style=\"text-align: start;\"\u003e\u003cimg style=\"float: none;\" alt=\"\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0652\/6245\/2965\/files\/0f1194fe-eec8-4f05-aea9-3818c7c3b146_1024x1024.jpg?v=1755196634\"\u003e\u003c\/div\u003e\n\u003ch2\u003eOptical Path\u003c\/h2\u003e\n\u003cdiv style=\"text-align: start;\"\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0652\/6245\/2965\/files\/eab23c07-a3ca-4aed-86c7-28b449215324_1024x1024.jpg?v=1755196700\" alt=\"\" style=\"float: none;\"\u003e\u003c\/div\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003ch2\u003eSpot Diagram\u003c\/h2\u003e\n\u003cdiv style=\"text-align: start;\"\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0652\/6245\/2965\/files\/2cff05db-8e5d-439a-b4f4-17a780185ae3_1024x1024.jpg?v=1755196728\" alt=\"\" style=\"float: none;\"\u003e\u003c\/div\u003e\n\u003cdiv style=\"text-align: start;\"\u003e\u003cbr\u003e\u003c\/div\u003e\n\u003ch3 style=\"text-align: start;\"\u003eIn the box\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli style=\"text-align: start;\"\u003e91F OTA\u003c\/li\u003e\n\u003cli style=\"text-align: start;\"\u003ePhotographic adapters\u003c\/li\u003e\n\u003cli style=\"text-align: start;\"\u003e1.25'' 45* erecting prism\u003c\/li\u003e\n\u003cli style=\"text-align: start;\"\u003e8mm eyepiece\u003c\/li\u003e\n\u003cli style=\"text-align: start;\"\u003e20mm eyepiece\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cdiv style=\"text-align: start;\"\u003e\u003cbr\u003e\u003c\/div\u003e\n\u003cdiv style=\"text-align: start;\"\u003e\n\u003ch3\u003eWarranty \u0026amp; Manuals\u003c\/h3\u003e\n\u003cp\u003eAskar Warranty\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"text-align: start;\"\u003e\u003ca rel=\"noopener\" href=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0652\/6245\/2965\/files\/Askar_91F_User_Manual_EN.pdf?v=1755197185\" target=\"_blank\"\u003e91F Flat-Field User's Manual\u003c\/a\u003e\u003c\/div\u003e","brand":"Askar","offers":[{"title":"Default Title","offer_id":47550539399397,"sku":"ASK-91F","price":1399.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0652\/6245\/2965\/files\/Askar91f-1.png?v=1777045198","url":"https:\/\/istronomyplus.com\/products\/ask-91f","provider":"Astronomy Plus – Telescopes \u0026 Astrophotography Canada","version":"1.0","type":"link"}