{"product_id":"askar-131f-flat-field-quadruplet-astrograph","title":"Askar 131F Flat-Field Quadruplet Astrograph","description":"\u003ch2\u003eAskar 131F Flat-Field Quadruplet Astrograph — 131mm f\/7.5\u003c\/h2\u003e\n\n\u003cp\u003eThe \u003cstrong\u003eAskar 131F Flat-Field\u003c\/strong\u003e is a premium 131mm aperture quadruplet APO astrograph designed for serious deep-sky astrophotographers and visual observers who want a large-aperture, plug-and-shoot instrument with no compromises. Built around a self-flattening quadruplet optical design — three elements at the front, one correcting element at the rear — the 131F delivers a flat, fully corrected image circle of 44mm, covering full-frame sensors without the need for a separate field flattener.\u003c\/p\u003e\n\n\u003cp\u003eWith a 983mm focal length at f\/7.5, the 131F occupies an ideal position for wide-field deep-sky imaging: enough aperture to collect serious light on faint nebulae and galaxies, and a focal ratio that keeps exposure times manageable. One piece of ED (extra-low dispersion) glass in the optical group keeps chromatic aberration tightly controlled across the full field.\u003c\/p\u003e\n\n\u003cp\u003eTrue to the Askar F Series philosophy, backfocus calculation is completely eliminated. Simply attach your camera adapter, achieve focus, and begin imaging — no spacer math, no flattener purchase required. The included photographic extension tube features a built-in 2-inch filter thread and ships with both M48×0.75 and M54×0.75 adapter options, covering a wide range of DSLR and dedicated astronomy cameras.\u003c\/p\u003e\n\n\u003cp\u003eThe mechanical package is equally well considered: a precision 3-inch rack-and-pinion focuser with 1:10 fine-focus adjustment, a built-in 360° camera rotator, a retractable dew shield, two finder scope bases, and a 300mm Losmandy-style dovetail plate — all finished in the iconic Askar blue-and-white CNC-machined tube body.\u003c\/p\u003e\n\n\u003ch2\u003eWho Is This Product Best For?\u003c\/h2\u003e\n\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eIntermediate and advanced astrophotographers\u003c\/strong\u003e who want to step up to a large-aperture, full-frame-capable astrograph without the complexity of external flatteners or backfocus calculations.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eDeep-sky imagers\u003c\/strong\u003e targeting nebulae, galaxy clusters, and large emission regions who want both resolution and field width in a single instrument.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eOne-scope-for-everything users\u003c\/strong\u003e — the 131F performs equally well for visual observing with standard 1.25\" and 2\" eyepieces, making it genuinely dual-purpose.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eImagers who use full-frame cameras\u003c\/strong\u003e — the 44mm image circle fully covers Sony, Nikon, and Canon full-frame sensors as well as large dedicated astronomy sensors.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eObservers who prefer a clean, streamlined workflow\u003c\/strong\u003e — the self-flattening design removes setup variables and lets you focus on the sky.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eWhy Choose the Askar 131F?\u003c\/h2\u003e\n\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eSelf-flattening quadruplet design\u003c\/strong\u003e — no separate field flattener to buy, no backfocus distance to calculate. Attach and shoot.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFull-frame sensor coverage\u003c\/strong\u003e — the 44mm image circle covers all modern full-frame DSLR and mirrorless sensors as well as large-format dedicated astronomy cameras.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eED glass chromatic control\u003c\/strong\u003e — a single ED element in the quadruplet group suppresses false colour across the entire image field.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eBuilt-in 360° camera rotator\u003c\/strong\u003e — frame your target at any angle without repositioning the entire telescope.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePremium 3\" R\u0026amp;P focuser with 1:10 fine adjustment\u003c\/strong\u003e — large-format, low-flex focuser suited to heavy camera payloads.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eDual-purpose: imaging and visual\u003c\/strong\u003e — the included 1.25\"\/2\" visual adapter makes the 131F a capable visual telescope alongside its imaging role.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eComprehensive standard package\u003c\/strong\u003e — tube rings, handle, 300mm Losmandy dovetail plate, and photographic adapter set are all included.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eRetractable dew shield\u003c\/strong\u003e — practical field protection without adding to transport length.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eRecommended Uses\u003c\/h2\u003e\n\n\u003cul\u003e\n  \u003cli\u003eWide-field deep-sky astrophotography (nebulae, galaxy groups, star-forming regions)\u003c\/li\u003e\n  \u003cli\u003eFull-frame DSLR and mirrorless astrophotography\u003c\/li\u003e\n  \u003cli\u003eDedicated astronomy camera imaging (mono and colour sensors)\u003c\/li\u003e\n  \u003cli\u003eNarrowband and broadband filter imaging (2\" filter thread built-in)\u003c\/li\u003e\n  \u003cli\u003eVisual deep-sky observing with 1.25\" and 2\" eyepieces\u003c\/li\u003e\n  \u003cli\u003eDual-rig or multi-telescope observatory setups\u003c\/li\u003e\n  \u003cli\u003eAstrophotography club and outreach use\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eCompatibility and Accessory Notes\u003c\/h2\u003e\n\n\u003cp\u003e\u003cstrong\u003eCamera compatibility:\u003c\/strong\u003e The 131F ships with M48×0.75 and M54×0.75 photographic adapters. DSLR users will need their camera's standard T-ring. Dedicated astronomy camera users with M42, M54, or M48 connections are directly supported. The built-in 2-inch filter thread on the extension tube accepts standard 2\" astronomy filters.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eMount compatibility:\u003c\/strong\u003e The included 300mm Losmandy-style dovetail plate is compatible with any mount that accepts a standard Losmandy D-plate saddle. At 7.9kg (OTA) and 9.4kg gross, a robust equatorial mount — such as a Sky-Watcher EQ6-R, iOptron CEM70, or equivalent — is recommended for imaging use.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eOptional accessories:\u003c\/strong\u003e The Askar 131F 0.74× reducer is available separately to bring the system to approximately f\/5.6 for faster imaging. Electronic focuser motor adapters are compatible with the 3\" focuser for remote or automated focus control.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eGuiding:\u003c\/strong\u003e Two built-in finder bases allow a guide scope to be mounted directly on the tube. Dedicated guide scopes such as the Askar 52mm guide scope series are compatible.\u003c\/p\u003e\n\n\u003ch2\u003eImportant Limitations\u003c\/h2\u003e\n\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eWeight requires a capable mount\u003c\/strong\u003e — at 9.4kg with rings and dovetail, this telescope needs a mid- to heavy-duty equatorial mount. It is not suited to lightweight travel mounts.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003ef\/7.5 is not ultrafast\u003c\/strong\u003e — for very faint targets in light-polluted skies, the optional 0.74× reducer (sold separately) is recommended to achieve f\/5.6 for shorter exposures.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eNot ideal for planetary or lunar imaging\u003c\/strong\u003e — the 983mm focal length and f\/7.5 ratio are optimized for wide-field deep sky; high-power planetary work benefits from longer focal lengths.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eLarge instrument\u003c\/strong\u003e — at up to 1026mm total length with the dew shield extended, this is a full-size observatory-class refractor. Travel and portability should be considered.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eNo electronic focuser included\u003c\/strong\u003e — the focuser is manual; an electronic focuser motor is available separately if motorized focus control is desired.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\n\n\u003cp\u003e\u003cstrong\u003eDo I need a field flattener with the Askar 131F?\u003c\/strong\u003e\u003cbr\u003e\nNo. The self-flattening quadruplet design produces a flat field natively. No separate flattener purchase is required, and no backfocus distance calculation is needed.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eDoes it cover a full-frame sensor?\u003c\/strong\u003e\u003cbr\u003e\nYes. The 44mm image circle fully covers all current full-frame DSLR, mirrorless, and dedicated astronomy camera sensors.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eIs it suitable for beginners?\u003c\/strong\u003e\u003cbr\u003e\nThe 131F is best suited to intermediate or advanced users who already have a capable equatorial mount and some experience with astrophotography. The self-flattening design does remove significant complexity, but the telescope's size, weight, and price point are more appropriate for experienced observers.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eWhat camera connections does it support?\u003c\/strong\u003e\u003cbr\u003e\nThe standard adapters cover M48×0.75 and M54×0.75 connections. DSLR users need a standard camera T-ring. Most dedicated astronomy cameras (ZWO, QHY, Player One, etc.) with M54 or M48 connections attach directly.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eCan I use it for visual observing?\u003c\/strong\u003e\u003cbr\u003e\nYes. The included 1.25\"\/2\" visual adapter lets you use standard eyepieces. The 131mm aperture and 983mm focal length provide excellent wide-field visual views of open clusters, nebulae, and galaxies.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eWhat mount do I need?\u003c\/strong\u003e\u003cbr\u003e\nA mount rated for at least 12–15kg of payload is recommended for imaging. Examples: Sky-Watcher EQ6-R Pro, iOptron CEM70, Rainbow RST-135, or equivalent.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eIs a reducer available?\u003c\/strong\u003e\u003cbr\u003e\nYes. The Askar 131F 0.74× reducer (sold separately) reduces the focal ratio to approximately f\/5.6, enabling faster exposures and a wider field of view.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eWhat makes it different from similarly priced astrographs?\u003c\/strong\u003e\u003cbr\u003e\nThe self-flattening quadruplet design is the key differentiator — you get a flat field across a 44mm image circle without buying or collimating an additional flattener. The built-in 360° rotator, 3\" focuser, and full accessory package also add significant real-world value over comparable bare OTAs.\u003c\/p\u003e\n\n\u003ch2\u003eOur Recommendation\u003c\/h2\u003e\n\n\u003cp\u003eAt Ontario Telescope and Accessories, we recommend the \u003cstrong\u003eAskar 131F Flat-Field\u003c\/strong\u003e for astrophotographers who are ready to step up to a large-aperture, full-frame-ready instrument and want the simplest possible imaging workflow. The self-flattening design is genuinely useful — it eliminates an entire category of compatibility and spacing problems that trip up even experienced imagers. Paired with a capable equatorial mount and a modern astronomy camera, the 131F is an exceptionally capable deep-sky imaging system.\u003c\/p\u003e\n\n\u003cp\u003eIf you are a beginner, a lighter and simpler telescope will serve you better while you develop your technique. If you primarily image planets or the Moon, a longer focal length instrument is a better match. But if wide-field deep-sky imaging on full-frame sensors is your goal, the Askar 131F is one of the most complete, ready-to-image packages available at this aperture class.\u003c\/p\u003e\n\n\u003ch2\u003eOptical Diagram Reports\u003c\/h2\u003e\n\n\u003cp\u003eThe following optical and mechanical diagrams are provided for customers who wish to review the Askar 131F's optical performance data, mechanical dimensions, connection specifications, and assembly details before purchasing or setting up the instrument.\u003c\/p\u003e\n\n\u003cimg src=\"https:\/\/omo-oss-image.thefastimg.com\/portal-saas\/pg2024111409483993253\/cms\/image\/8a883eef-96d8-4147-a206-fe1420dd4855.jpg\" alt=\"Askar 131F Product Size Diagram - mechanical dimensions and tube length measurements\" style=\"max-width:100%;display:block;margin:1em 0;\"\u003e\n\n\u003cimg src=\"https:\/\/omo-oss-image.thefastimg.com\/portal-saas\/pg2024111409483993253\/cms\/image\/a9e9b79d-844c-4873-9502-9cc87b6f3bf8.jpg\" alt=\"Askar 131F Product Size Diagram - additional mechanical dimensions\" style=\"max-width:100%;display:block;margin:1em 0;\"\u003e\n\n\u003cimg src=\"https:\/\/omo-oss-image.thefastimg.com\/portal-saas\/pg2024111409483993253\/cms\/image\/dbaae082-9703-4ccc-a319-b6dedcb3e3d8.jpg\" alt=\"Askar 131F Connection Diagram - photographic adapter and camera connection threading specifications\" style=\"max-width:100%;display:block;margin:1em 0;\"\u003e\n\n\u003cimg src=\"https:\/\/omo-oss-image.thefastimg.com\/portal-saas\/pg2024111409483993253\/cms\/image\/37f4ab88-3b9a-4c66-88f2-1674920272bb.jpg\" alt=\"Askar 131F Locking Screw Position Diagram - focuser and adapter locking screw locations\" style=\"max-width:100%;display:block;margin:1em 0;\"\u003e\n\n\u003cimg src=\"https:\/\/omo-oss-image.thefastimg.com\/portal-saas\/pg2024111409483993253\/cms\/image\/1acc5643-0b25-4789-a1b5-11c889ba55e2.jpg\" alt=\"Askar 131F Electronic Focuser Assembly Diagram - motorized focuser motor mounting instructions\" style=\"max-width:100%;display:block;margin:1em 0;\"\u003e\n\n\u003cimg src=\"https:\/\/omo-oss-image.thefastimg.com\/portal-saas\/pg2024111409483993253\/cms\/image\/e9cb86dc-bee7-488c-89ef-47160eaf5769.jpg\" alt=\"Askar 131F Optical Path Diagram - quadruplet lens group layout and light path illustration\" style=\"max-width:100%;display:block;margin:1em 0;\"\u003e\n\n\u003cimg src=\"https:\/\/omo-oss-image.thefastimg.com\/portal-saas\/pg2024111409483993253\/cms\/image\/96389167-369e-4ff4-bbd2-43768e5ac17d.jpg\" alt=\"Askar 131F Spot Diagram - optical star spot performance across full-frame image circle\" style=\"max-width:100%;display:block;margin:1em 0;\"\u003e","brand":"Askar","offers":[{"title":"Default Title","offer_id":53154388476015,"sku":"131F-FLAT-FIELD","price":2798.6,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/1114d666-31b5-46c4-85c4-3c57ff6d48e7.png?v=1779666429","url":"https:\/\/ontariotelescope.com\/products\/askar-131f-flat-field-quadruplet-astrograph","provider":"Ontario Telescope and Accessories","version":"1.0","type":"link"}