{"title":"F Series","description":"","products":[{"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"},{"product_id":"askar-111f-flat-field-quadruplet-astrograph","title":"Askar 111F Flat-Field Quadruplet Astrograph","description":"\u003ch2\u003eAskar 111F Flat-Field Quadruplet Astrograph — 111mm f\/6.9\u003c\/h2\u003e\n\n\u003cp\u003eThe \u003cstrong\u003eAskar 111F Flat-Field\u003c\/strong\u003e is a 111mm aperture, 766mm focal length quadruplet APO astrograph built around Askar's proven self-flattening design philosophy. At a native f\/6.9 focal ratio, it sits between the compact 91F and the larger 131F in the F Series lineup — offering meaningful aperture and a relatively fast ratio in a package that tops out under 6kg with rings and dovetail, making it compatible with a wider range of equatorial mounts than its larger sibling.\u003c\/p\u003e\n\n\u003cp\u003eThe optical design uses four air-spaced elements — three in the front group and one correcting element in the rear — with one piece of ED glass to manage chromatic aberration across the full field. An internal baffle in the tube body further reduces stray light, and the system natively supports a 44mm image circle covering full-frame sensors. Like all F Series telescopes, it requires no separate field flattener and no backfocus calculation: connect your camera, achieve focus, and begin imaging.\u003c\/p\u003e\n\n\u003cp\u003eThe mechanical package is comprehensive: a 3\" rack-and-pinion focuser with 1:10 fine adjustment, a built-in 360° camera rotator, a retractable dew shield, two finder scope bases on the tube plus one on the handle, and a 300mm Vixen-style dovetail plate with 1\/4\" and 3\/8\" tripod screw holes. The tube body is precision CNC-machined in the signature Askar blue-and-white finish.\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 astrophotographers\u003c\/strong\u003e stepping up from a smaller instrument who want full-frame sensor coverage with no flattener complexity.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eDeep-sky imagers\u003c\/strong\u003e targeting nebulae, galaxy groups, and emission regions where 111mm of aperture provides meaningful light collection advantage over sub-100mm instruments.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMount-limited users\u003c\/strong\u003e who want more aperture than the 91F but need to stay within the payload range of mounts like the Sky-Watcher HEQ5, iOptron CEM40, or equivalent.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eDual-purpose users\u003c\/strong\u003e who want both astrophotography and visual observing capability in one instrument, since the 111F accepts standard 1.25\" and 2\" eyepieces.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eBudget-conscious upgraders\u003c\/strong\u003e who want a large-image-circle full-frame astrograph at a lower price point than the 131F.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eWhy Choose the Askar 111F?\u003c\/h2\u003e\n\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eSelf-flattening quadruplet\u003c\/strong\u003e — no additional flattener needed, no backfocus distance to calculate. Attach your camera and shoot.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e44mm full-frame image circle\u003c\/strong\u003e — covers full-frame DSLR, mirrorless, and large dedicated astronomy camera sensors.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eED glass chromatic control\u003c\/strong\u003e — one 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 moving the telescope.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e3\" R\u0026amp;P focuser with 1:10 fine adjustment\u003c\/strong\u003e — large-format, low-flex focuser with fine control protective cap.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMultiple finder base positions\u003c\/strong\u003e — finder scope can be repositioned between handle slot and focuser-side bases without disassembly.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eLighter than the 131F\u003c\/strong\u003e — at 6.76kg gross (with rings and Vixen dovetail), compatible with a broader range of imaging mounts.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e2\" filter thread built-in\u003c\/strong\u003e — the photographic extension tube accepts standard 2-inch astronomy filters directly.\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 clusters, emission regions)\u003c\/li\u003e\n  \u003cli\u003eFull-frame DSLR and mirrorless astrophotography\u003c\/li\u003e\n  \u003cli\u003eDedicated astronomy camera imaging (ZWO, QHY, Player One, Touptek, etc.)\u003c\/li\u003e\n  \u003cli\u003eNarrowband and broadband filter imaging\u003c\/li\u003e\n  \u003cli\u003eVisual deep-sky observing with 1.25\" and 2\" eyepieces\u003c\/li\u003e\n  \u003cli\u003eModerate-payload equatorial mount imaging setups\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eCompatibility and Accessory Notes\u003c\/h2\u003e\n\n\u003cp\u003e\u003cstrong\u003eCamera connections:\u003c\/strong\u003e Ships with M48×0.75 and M54×0.75 photographic adapters. DSLR users need a standard camera T-ring. The built-in 2\" filter thread on the extension tube accepts standard astronomy filters. Most dedicated astronomy cameras with M54 or M48 nose threads connect directly.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eMount compatibility:\u003c\/strong\u003e The 300mm Vixen-style dovetail plate fits any Vixen-compatible saddle. The 1\/4\" and 3\/8\" holes allow direct tripod mounting. At 6.76kg gross, mounts rated for 10–12kg imaging payload are appropriate — such as the Sky-Watcher HEQ5 Pro, iOptron CEM40, ZWO AM5, or equivalent.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eOptional accessories:\u003c\/strong\u003e The Askar 111F 0.74× Reducer (sold separately) drops the system to approximately f\/5.1 (566mm focal length) for wider-field, faster imaging. An electronic focuser motor is available separately for remote focus control.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eGuiding:\u003c\/strong\u003e Two finder bases on the focuser body plus the handle slot provide three guide scope mounting positions. Compatible with Askar 52mm guide scope series and other standard guide scopes.\u003c\/p\u003e\n\n\u003ch2\u003eImportant Limitations\u003c\/h2\u003e\n\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003ef\/6.9 is not ultrafast\u003c\/strong\u003e — for very faint targets in light-polluted skies, the optional 0.74× reducer (sold separately) is recommended.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eNot ideal for planetary or lunar imaging\u003c\/strong\u003e — optimized for wide-field deep sky, not high-magnification planetary detail.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eNo electronic focuser included\u003c\/strong\u003e — motorized focus requires a separately purchased focuser motor.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eNot a beginner instrument\u003c\/strong\u003e — most appropriate for users with an equatorial mount and some astrophotography experience.\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?\u003c\/strong\u003e\u003cbr\u003eNo. The self-flattening quadruplet design produces a flat field natively across the 44mm image circle.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eDoes it cover full-frame sensors?\u003c\/strong\u003e\u003cbr\u003eYes. The 44mm image circle covers all current full-frame DSLR, mirrorless, and dedicated astronomy camera sensors.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eWhat mount do I need?\u003c\/strong\u003e\u003cbr\u003eA mount rated for 10–12kg payload is recommended for imaging. Examples: Sky-Watcher HEQ5 Pro, iOptron CEM40, ZWO AM5N, or equivalent.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eHow does the 111F compare to the 91F?\u003c\/strong\u003e\u003cbr\u003eThe 111F has 22% more aperture (111mm vs 91mm), a slightly faster native ratio (f\/6.9 vs f\/6.7), and a longer 766mm focal length vs 609mm. It is heavier (5.74kg net vs 3.92kg) and does not include eyepieces or an erecting prism in the standard package. The 91F is better for users with smaller mounts or who want a more complete visual\/travel kit out of the box.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eHow does the 111F compare to the 131F?\u003c\/strong\u003e\u003cbr\u003eThe 131F has more aperture (131mm) and a longer focal length (983mm) but is significantly heavier (7.9kg net) and requires a heavier-duty mount. The 111F is the better choice for users with mid-weight mounts who still want full-frame coverage.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eIs a reducer available?\u003c\/strong\u003e\u003cbr\u003eYes. The Askar 111F 0.74× Reducer (sold separately) reduces the system to f\/5.1 and 566mm focal length.\u003c\/p\u003e\n\n\u003ch2\u003eOur Recommendation\u003c\/h2\u003e\n\n\u003cp\u003eAt Ontario Telescope and Accessories, we recommend the \u003cstrong\u003eAskar 111F Flat-Field\u003c\/strong\u003e for astrophotographers who want a meaningful aperture upgrade over a 60–91mm instrument while keeping the system weight manageable for mid-range equatorial mounts. The self-flattening design eliminates the most common source of setup complexity for newer imagers, and the full-frame image circle means the optics will not limit you as your camera equipment evolves. It is a strong all-round deep-sky imaging platform at a competitive price point in the 100–120mm aperture class.\u003c\/p\u003e\n\n\u003ch2\u003eOptical Diagram Reports\u003c\/h2\u003e\n\n\u003cp\u003eThe following diagrams are provided for customers who wish to review the optical performance data, mechanical dimensions, and connection specifications of the Askar 111F 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\/454295a5-664d-43a2-9b8e-1b65a715a593.jpg\" alt=\"Askar 111F Product Size Diagram - tube length and mechanical dimensions\" style=\"max-width:100%;display:block;margin:1em 0;\"\u003e\n\u003cimg src=\"https:\/\/omo-oss-image.thefastimg.com\/portal-saas\/pg2024111409483993253\/cms\/image\/39e3d53e-59fa-4ba9-bb6a-d46e147a0f0b.jpg\" alt=\"Askar 111F Product Size Diagram - additional dimension reference\" style=\"max-width:100%;display:block;margin:1em 0;\"\u003e\n\u003cimg src=\"https:\/\/omo-oss-image.thefastimg.com\/portal-saas\/pg2024111409483993253\/cms\/image\/d77cda7c-afa8-4052-9c88-e7ad4d7a8ac1.jpg\" alt=\"Askar 111F Connection Diagram - photographic adapter and camera thread connection details\" style=\"max-width:100%;display:block;margin:1em 0;\"\u003e\n\u003cimg src=\"https:\/\/omo-oss-image.thefastimg.com\/portal-saas\/pg2024111409483993253\/cms\/image\/37f4ab88-3b9a-4c66-88f2-1674920272bb.jpg\" alt=\"Askar 111F Locking Screw Position Diagram - focuser and adapter lock locations\" style=\"max-width:100%;display:block;margin:1em 0;\"\u003e\n\u003cimg src=\"https:\/\/omo-oss-image.thefastimg.com\/portal-saas\/pg2024111409483993253\/cms\/image\/1acc5643-0b25-4789-a1b5-11c889ba55e2.jpg\" alt=\"Askar 111F Electronic Focuser Assembly Diagram - motor mounting instructions\" style=\"max-width:100%;display:block;margin:1em 0;\"\u003e\n\u003cimg src=\"https:\/\/omo-oss-image.thefastimg.com\/portal-saas\/pg2024111409483993253\/cms\/image\/d7da6964-5f63-4a1b-add1-645d41eba620.jpg\" alt=\"Askar 111F Optical Path Diagram - quadruplet lens group and light path layout\" style=\"max-width:100%;display:block;margin:1em 0;\"\u003e\n\u003cimg src=\"https:\/\/omo-oss-image.thefastimg.com\/portal-saas\/pg2024111409483993253\/cms\/image\/d3529dd7-ba1a-4553-af4b-787d4e747dc3.jpg\" alt=\"Askar 111F Spot Diagram - 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":53154393686127,"sku":"111F-FLAT-FIELD","price":2098.6,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/ee178691-b536-4f04-81d1-9acd6a365330.png?v=1779667136"},{"product_id":"askar-91f-flat-field-quadruplet-astrograph","title":"Askar 91F Flat-Field Quadruplet Astrograph","description":"\u003ch2\u003eAskar 91F Flat-Field Quadruplet Astrograph — 91mm f\/6.7\u003c\/h2\u003e\n\n\u003cp\u003eThe \u003cstrong\u003eAskar 91F Flat-Field\u003c\/strong\u003e is a 91mm aperture, 609mm focal length quadruplet APO astrograph and the most accessible telescope in the Askar F Series. At a native f\/6.7 focal ratio, it combines a compact and lightweight build — just 3.92kg OTA — with the same self-flattening, full-frame-capable optical performance that defines the entire F Series lineup.\u003c\/p\u003e\n\n\u003cp\u003eThe four-element optical design (three front elements, one rear correcting element) includes one piece of ED glass to suppress chromatic aberration. The system natively supports a 44mm image circle covering full-frame sensors with no external flattener required and no backfocus calculation needed. Simply attach your camera, achieve focus, and begin imaging.\u003c\/p\u003e\n\n\u003cp\u003eThe 91F is the most complete package in the F Series out of the box: in addition to the standard photographic extension tube with M48×0.75 and M54×0.75 adapters, it ships with an 8mm eyepiece (76×), a 20mm eyepiece (30×), and a 1.25\" 45° erecting prism — making it immediately ready for visual observing, birdwatching, and terrestrial use the moment it arrives.\u003c\/p\u003e\n\n\u003cp\u003eThe mechanical package includes a 3\" R\u0026amp;P focuser with 1:10 fine adjustment, a 360° camera rotator, a retractable dew shield, a matting-felt-lined tube interior, two finder bases on the focuser plus a handle slot, and a 230mm Vixen-style dovetail plate with 1\/4\" and 3\/8\" tripod holes. The exterior features the signature Askar blue-and-white CNC-machined finish.\u003c\/p\u003e\n\n\u003ch2\u003eWho Is This Product Best For?\u003c\/h2\u003e\n\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eBeginner to intermediate astrophotographers\u003c\/strong\u003e who want a full-frame-capable, self-flattening instrument with no setup complexity.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eTravel and portable rig users\u003c\/strong\u003e — at 3.92kg OTA and a maximum length under 640mm with dew shield extended, it pairs well with compact travel mounts like the ZWO AM5, iOptron HEM27, Sky-Watcher Star Adventurer GTi, and similar.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eDual-purpose visual and imaging users\u003c\/strong\u003e — the included eyepiece and erecting prism kit makes it ready for daytime spotting and nighttime visual observing right out of the box.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eBirders and nature observers\u003c\/strong\u003e looking for a versatile, optically excellent spotting scope that doubles as an astrograph.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eDeep-sky imagers on smaller mounts\u003c\/strong\u003e who need a flat-field full-frame instrument within a tight weight budget.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eWhy Choose the Askar 91F?\u003c\/h2\u003e\n\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eSelf-flattening quadruplet\u003c\/strong\u003e — no separate flattener, no backfocus calculation. Attach and shoot.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e44mm full-frame image circle\u003c\/strong\u003e — covers all modern full-frame DSLR, mirrorless, and dedicated astronomy sensors.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eLightest F Series telescope\u003c\/strong\u003e — at 3.92kg OTA (4.52kg gross), suitable for the widest range of mounts including travel-grade systems.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMost complete standard package\u003c\/strong\u003e — the 91F includes 8mm and 20mm eyepieces plus a 1.25\" erecting prism, unlike the larger F Series models.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eED glass chromatic control\u003c\/strong\u003e — one ED element minimizes false colour across the full image field.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eBuilt-in 360° rotator\u003c\/strong\u003e — frame targets at any angle without repositioning the mount.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMatting felt interior\u003c\/strong\u003e — stray light absorption lining inside the tube for better contrast.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eRetractable dew shield\u003c\/strong\u003e — compact for transport, extended for use.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eTripod-mountable dovetail\u003c\/strong\u003e — 230mm Vixen plate with 1\/4\" and 3\/8\" screw holes for direct tripod use.\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, star clusters, large emission regions)\u003c\/li\u003e\n  \u003cli\u003eFull-frame DSLR, mirrorless, and dedicated astronomy camera imaging\u003c\/li\u003e\n  \u003cli\u003eNarrowband and broadband filter imaging (built-in 2\" filter thread)\u003c\/li\u003e\n  \u003cli\u003eVisual deep-sky observing with included 8mm and 20mm eyepieces\u003c\/li\u003e\n  \u003cli\u003eBirdwatching, wildlife, and terrestrial spotting\u003c\/li\u003e\n  \u003cli\u003eTravel and portable mount setups\u003c\/li\u003e\n  \u003cli\u003eBeginner astrophotography and astronomy outreach\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eCompatibility and Accessory Notes\u003c\/h2\u003e\n\n\u003cp\u003e\u003cstrong\u003eCamera connections:\u003c\/strong\u003e Ships with M48×0.75 and M54×0.75 adapters. DSLR users need a standard T-ring. Dedicated astronomy cameras with M54 or M48 connections attach directly. Built-in 2\" filter thread on the extension tube accepts standard astronomy filters.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eMount compatibility:\u003c\/strong\u003e The 230mm Vixen dovetail fits any Vixen-compatible saddle. The 1\/4\" and 3\/8\" tripod holes allow direct tripod mounting without a mount at all. At 4.52kg gross, compatible with lightweight mounts including ZWO AM5, iOptron HEM27, Sky-Watcher HEQ5, Star Adventurer GTi, and similar. A mount rated for at least 6–8kg payload is recommended for imaging.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eOptional accessories:\u003c\/strong\u003e The Askar 91F 0.75× Reducer (sold separately) brings the system to f\/5 and 455mm focal length for wider-field, faster imaging. An electronic focuser motor is available separately.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eIncluded visual accessories:\u003c\/strong\u003e 8mm eyepiece (76× magnification), 20mm eyepiece (30× magnification), and 1.25\" 45° erecting prism for correct-image terrestrial and astronomical viewing.\u003c\/p\u003e\n\n\u003ch2\u003eImportant Limitations\u003c\/h2\u003e\n\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eSmaller aperture than 111F\/131F\u003c\/strong\u003e — 91mm collects less light than larger F Series instruments; exposures will be longer on faint targets. Consider the optional 0.75× reducer or a larger telescope for very faint, small-scale objects.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003ef\/6.7 is moderate speed\u003c\/strong\u003e — not ultrafast; the optional 0.75× reducer (sold separately) brings it to f\/5 for shorter exposures.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eNot ideal for planetary imaging\u003c\/strong\u003e — the 609mm focal length is optimized for wide-field deep sky, not high-magnification planetary detail.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eNo electronic focuser included\u003c\/strong\u003e — motorized focus requires a separately purchased motor.\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 flattener?\u003c\/strong\u003e\u003cbr\u003eNo. The self-flattening quadruplet produces a flat field across the 44mm image circle natively.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eDoes it cover full-frame sensors?\u003c\/strong\u003e\u003cbr\u003eYes. The 44mm image circle fully covers all current full-frame DSLR, mirrorless, and dedicated astronomy cameras.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eIs it good for beginners?\u003c\/strong\u003e\u003cbr\u003eYes — it is the most beginner-friendly instrument in the F Series. The included eyepieces and erecting prism mean it can be used for visual observing immediately, and the self-flattening design removes the most common astrophotography setup hurdle.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eWhat mount do I need?\u003c\/strong\u003e\u003cbr\u003eFor imaging, a mount rated for at least 6–8kg payload is recommended. For visual use only, it can be used on a camera tripod via the built-in tripod screw holes.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eIs a reducer available?\u003c\/strong\u003e\u003cbr\u003eYes. The Askar 91F 0.75× Reducer (sold separately) reduces the system to f\/5 and 455mm focal length.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eHow does it compare to the 111F?\u003c\/strong\u003e\u003cbr\u003eThe 91F is lighter (3.92kg vs 5.74kg), shorter, includes eyepieces and an erecting prism, and is better suited for smaller mounts and travel. The 111F has more aperture and a longer focal length for more resolution on smaller targets.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eCan I use it for birdwatching?\u003c\/strong\u003e\u003cbr\u003eYes. The included 20mm eyepiece and erecting prism give a correct-image view for terrestrial spotting. It functions as an excellent spotting scope in addition to its astronomy role.\u003c\/p\u003e\n\n\u003ch2\u003eOur Recommendation\u003c\/h2\u003e\n\n\u003cp\u003eAt Ontario Telescope and Accessories, we recommend the \u003cstrong\u003eAskar 91F Flat-Field\u003c\/strong\u003e as the best entry point into the F Series for most buyers. It is the lightest, most portable, and most complete package — ready for visual observing, birdwatching, and astrophotography the moment it arrives. If you are using a compact or travel mount, or you want one instrument that handles astronomy and daytime optics equally well, the 91F is an outstanding choice.\u003c\/p\u003e\n\n\u003cp\u003eIf you need more aperture for fainter targets or higher resolution and have a heavier mount, consider the 111F or 131F. But for first-time F Series buyers and travel users, the 91F delivers the full F Series experience in the most accessible package.\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 91F’s optical performance, mechanical dimensions, and connection specifications.\u003c\/p\u003e\n\n\u003cimg src=\"https:\/\/omo-oss-image.thefastimg.com\/portal-saas\/pg2024111409483993253\/cms\/image\/6d3433e9-069f-4e8f-8fe5-f64659c95b6e.jpg\" alt=\"Askar 91F Product Size Diagram - tube length and mechanical dimensions\" style=\"max-width:100%;display:block;margin:1em 0;\"\u003e\n\u003cimg src=\"https:\/\/omo-oss-image.thefastimg.com\/portal-saas\/pg2024111409483993253\/cms\/image\/d8b7fe34-d5d0-4555-bbc9-ead405dfacf2.jpg\" alt=\"Askar 91F Connection Diagram - photographic adapter and camera thread connection details\" style=\"max-width:100%;display:block;margin:1em 0;\"\u003e\n\u003cimg src=\"https:\/\/omo-oss-image.thefastimg.com\/portal-saas\/pg2024111409483993253\/cms\/image\/37f4ab88-3b9a-4c66-88f2-1674920272bb.jpg\" alt=\"Askar 91F Locking Screw Position Diagram - focuser and adapter lock locations\" style=\"max-width:100%;display:block;margin:1em 0;\"\u003e\n\u003cimg src=\"https:\/\/omo-oss-image.thefastimg.com\/portal-saas\/pg2024111409483993253\/cms\/image\/1acc5643-0b25-4789-a1b5-11c889ba55e2.jpg\" alt=\"Askar 91F Electronic Focuser Assembly Diagram - motor mounting instructions\" style=\"max-width:100%;display:block;margin:1em 0;\"\u003e\n\u003cimg src=\"https:\/\/omo-oss-image.thefastimg.com\/portal-saas\/pg2024111409483993253\/cms\/image\/fabf66d1-bbc7-47d2-95d9-13cbfcf8d59e.jpg\" alt=\"Askar 91F Optical Path Diagram - quadruplet lens group and light path layout\" style=\"max-width:100%;display:block;margin:1em 0;\"\u003e\n\u003cimg src=\"https:\/\/omo-oss-image.thefastimg.com\/portal-saas\/pg2024111409483993253\/cms\/image\/9204b293-5dea-45bd-a45d-91db45661241.jpg\" alt=\"Askar 91F Spot Diagram - star spot performance across the full-frame image circle\" style=\"max-width:100%;display:block;margin:1em 0;\"\u003e","brand":"Askar","offers":[{"title":"Default Title","offer_id":53154396504175,"sku":"91F-FLAT-FIELD","price":1398.6,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/4a0aa511-087e-46a0-897a-b099e77a876e.png_560xaf.webp?v=1779668266"},{"product_id":"askar-131f-0-74-focal-reducer","title":"Askar 131F 0.74× Focal Reducer","description":"\u003ch2\u003eAskar 131F 0.74× Focal Reducer — For the Askar 131F Flat-Field Astrograph\u003c\/h2\u003e\n\n\u003cp\u003eThe \u003cstrong\u003eAskar 131F 0.74× Reducer\u003c\/strong\u003e is a dedicated focal reducer designed exclusively for the Askar 131F Flat-Field astrograph. It reduces the 131F’s native f\/7.5 focal ratio down to f\/5.6, shortening the effective focal length from 983mm to 733.6mm. This delivers a wider field of view and significantly faster exposures — roughly 80% of the original exposure time — making it particularly valuable for capturing large nebulae, expansive star fields, faint emission structures, and fast-moving or time-sensitive celestial events.\u003c\/p\u003e\n\n\u003cp\u003eIn addition to reducing the focal ratio, the reducer incorporates built-in field-flattening correction that eliminates field curvature across the 44mm full-frame image circle. Stars remain sharp and round from the centre of the frame to the corners, with no additional flattener required at the reduced focal ratio.\u003c\/p\u003e\n\n\u003cp\u003eThe optical design uses a triplet lens group for smooth, well-corrected reduction across the full field. The standard back focus distance is 55mm measured from the M48×0.75 male thread. Both ends of the reducer body feature M72×1 threads. The package includes M54×0.75 and M48×0.75 adapter rings for direct connection to the 131F’s photographic extension tube, and the rear adapter ring has a built-in M48×0.75 standard 2\" filter thread for direct filter installation. The body is precision CNC-machined and ships with protective metal thread caps on both ends.\u003c\/p\u003e\n\n\u003ch2\u003eWho Is This Product Best For?\u003c\/h2\u003e\n\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eAskar 131F owners\u003c\/strong\u003e who image large nebulae, emission regions, or wide star fields and want a broader field of view without changing telescopes.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eImagers in light-polluted skies\u003c\/strong\u003e who benefit from the faster f\/5.6 ratio to shorten sub-exposure times.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eNarrowband and broadband filter users\u003c\/strong\u003e who want the faster ratio for more efficient filter imaging.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eAstrophotographers\u003c\/strong\u003e who want to switch between the native f\/7.5 (for tighter framing) and f\/5.6 (for wider field) without buying a second telescope.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eWhy Choose the Askar 131F 0.74× Reducer?\u003c\/h2\u003e\n\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eDedicated design\u003c\/strong\u003e — optically optimized specifically for the 131F, not a generic reducer. Delivers consistent correction across the full 44mm image circle at the reduced ratio.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eBuilt-in field flattening\u003c\/strong\u003e — no additional flattener needed at f\/5.6; the reducer handles both reduction and correction simultaneously.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFaster imaging\u003c\/strong\u003e — f\/5.6 vs f\/7.5 means roughly 44% less exposure time needed for the same signal level.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eWider field\u003c\/strong\u003e — 733.6mm focal length vs 983mm gives approximately 26% more field width in each direction.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eStandard back focus\u003c\/strong\u003e — 55mm from M48 thread eliminates guesswork; direct adapter connections included in the box.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFilter-ready rear\u003c\/strong\u003e — built-in M48×0.75 thread accepts standard 2\" astronomy filters without an additional adapter.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eCNC precision body with dust caps\u003c\/strong\u003e — professional-grade build quality with protective metal end caps.\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 nebula imaging with the Askar 131F\u003c\/li\u003e\n  \u003cli\u003eLarge emission and reflection nebulae (Orion, Rosette, North America, etc.)\u003c\/li\u003e\n  \u003cli\u003eGalaxy groups and clusters requiring wider framing\u003c\/li\u003e\n  \u003cli\u003eNarrowband and broadband filter imaging in light-polluted sites\u003c\/li\u003e\n  \u003cli\u003eTime-lapse or short-exposure widefield astrophotography\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eCompatibility and Accessory Notes\u003c\/h2\u003e\n\n\u003cp\u003e\u003cstrong\u003eCompatible telescope:\u003c\/strong\u003e Askar 131F Flat-Field only. Not designed for use with any other telescope.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eConnection:\u003c\/strong\u003e The 131F’s photographic extension tube connects directly to the reducer via the included M54×0.75 or M48×0.75 adapter rings. Both end threads on the reducer body are M72×1.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eBack focus:\u003c\/strong\u003e 55mm from the base of the M48×0.75 male thread. No additional spacing calculation required when using the supplied adapters.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eFilter compatibility:\u003c\/strong\u003e The built-in rear M48×0.75 thread accepts standard 2\" (48mm) astronomy filters directly.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eCamera compatibility:\u003c\/strong\u003e Works with any camera system that connects via the included M54 or M48 adapter rings — DSLRs with T-rings, and dedicated astronomy cameras with M54 or M48 nose threads.\u003c\/p\u003e\n\n\u003ch2\u003eImportant Limitations\u003c\/h2\u003e\n\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003e131F only\u003c\/strong\u003e — this reducer is not compatible with the 91F, 111F, or any other telescope. Each F Series model has its own dedicated reducer.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eNot for visual observing\u003c\/strong\u003e — focal reducers are imaging-only accessories and are not used with eyepieces.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e55mm back focus must be respected\u003c\/strong\u003e — using spacers or adapters that change the back focus distance from the specified 55mm will degrade corner star quality.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\n\n\u003cp\u003e\u003cstrong\u003eWhat does the 0.74× reducer do to the 131F?\u003c\/strong\u003e\u003cbr\u003eIt reduces the focal length from 983mm to 733.6mm and the focal ratio from f\/7.5 to f\/5.6, giving a wider field of view and faster exposures.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eDoes it work on the 91F or 111F?\u003c\/strong\u003e\u003cbr\u003eNo. Each F Series telescope has its own dedicated reducer. The 91F uses the 0.75× Reducer and the 111F uses the 0.74× Reducer — both are different products.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eDo I still need a field flattener at f\/5.6?\u003c\/strong\u003e\u003cbr\u003eNo. The reducer has field-flattening correction built in and covers the full 44mm image circle with sharp stars to the corners.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eWhat is the back focus distance?\u003c\/strong\u003e\u003cbr\u003e55mm measured from the base of the M48×0.75 male thread on the rear of the reducer.\u003c\/p\u003e\n\n\u003ch2\u003eOur Recommendation\u003c\/h2\u003e\n\n\u003cp\u003eAt Ontario Telescope and Accessories, we consider the \u003cstrong\u003eAskar 131F 0.74× Reducer\u003c\/strong\u003e a worthwhile companion purchase for any 131F owner who does wide-field deep-sky imaging. The improvement in field width and exposure speed is significant, and the fact that it handles both reduction and field flattening in one unit keeps the imaging train simple. If you own a 131F and shoot large nebulae or work under moderate light pollution, this reducer will meaningfully expand what you can do with the telescope.\u003c\/p\u003e","brand":"Askar","offers":[{"title":"Default Title","offer_id":53154396668015,"sku":"131F-REDUCER-074X","price":418.6,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/39700a9a-6969-4a4b-bb2c-f65eb7ad5c26.png?v=1779667444"},{"product_id":"askar-111f-0-74-focal-reducer","title":"Askar 111F 0.74× Focal Reducer","description":"\u003ch2\u003eAskar 111F 0.74× Focal Reducer — For the Askar 111F Flat-Field Astrograph\u003c\/h2\u003e\n\n\u003cp\u003eThe \u003cstrong\u003eAskar 111F 0.74× Reducer\u003c\/strong\u003e is a dedicated focal reducer designed exclusively for the Askar 111F Flat-Field astrograph. It reduces the 111F’s native f\/6.9 focal ratio down to f\/5.1, shortening the effective focal length from 766mm to 566mm. This produces a wider field of view and a faster optical system that reduces exposure times — making it ideal for large nebulae, expansive emission regions, and imaging sessions where efficiency matters.\u003c\/p\u003e\n\n\u003cp\u003eThe reducer incorporates built-in field-flattening correction, eliminating field curvature and ensuring sharp, round stars from the centre of the frame all the way to the corners of a 44mm full-frame image circle. No additional flattener is required at the reduced focal ratio.\u003c\/p\u003e\n\n\u003cp\u003eThe optical design features a triplet lens group for smooth, well-corrected reduction. The standard back focus distance is 55mm from the M48×0.75 male thread. Both ends of the reducer body feature M68×1 threads. The 111F’s photographic extension tube connects directly via the included M54×0.75 and M48×0.75 adapter rings. The rear adapter ring has a built-in M48×0.75 standard 2\" filter thread. The body is precision CNC-machined and ships with protective metal thread caps on both ends.\u003c\/p\u003e\n\n\u003ch2\u003eWho Is This Product Best For?\u003c\/h2\u003e\n\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eAskar 111F owners\u003c\/strong\u003e who image large nebulae or wide star fields and want a broader field of view and faster exposures.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eImagers in light-polluted environments\u003c\/strong\u003e who benefit from the faster f\/5.1 ratio to shorten sub-exposure times.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eNarrowband and broadband filter users\u003c\/strong\u003e wanting more imaging efficiency from their 111F setup.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePhotographers who want flexibility\u003c\/strong\u003e — switching between the native f\/6.9 (for tighter framing and higher resolution) and f\/5.1 (for wider field) without a second telescope.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eWhy Choose the Askar 111F 0.74× Reducer?\u003c\/h2\u003e\n\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eDedicated design\u003c\/strong\u003e — optimized specifically for the 111F; delivers consistent, well-corrected performance across the full 44mm image circle at f\/5.1.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eBuilt-in field flattening\u003c\/strong\u003e — one accessory handles both reduction and corner correction simultaneously.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eSignificantly faster system\u003c\/strong\u003e — f\/5.1 vs f\/6.9 means roughly 45% less exposure time required for the same signal.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eWider field\u003c\/strong\u003e — 566mm vs 766mm focal length gives approximately 26% more field width per axis.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eStandard 55mm back focus\u003c\/strong\u003e — no spacing guesswork; direct adapter connections are included.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFilter-ready\u003c\/strong\u003e — built-in M48×0.75 rear thread accepts standard 2\" astronomy filters directly.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eCNC body with protective caps\u003c\/strong\u003e — professional build quality with dust-proof metal end caps.\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 nebula imaging with the Askar 111F\u003c\/li\u003e\n  \u003cli\u003eLarge emission and reflection nebulae\u003c\/li\u003e\n  \u003cli\u003eGalaxy groups and wide star fields requiring broader framing\u003c\/li\u003e\n  \u003cli\u003eNarrowband and broadband filter imaging\u003c\/li\u003e\n  \u003cli\u003eEfficient imaging from light-polluted sites\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eCompatibility and Accessory Notes\u003c\/h2\u003e\n\n\u003cp\u003e\u003cstrong\u003eCompatible telescope:\u003c\/strong\u003e Askar 111F Flat-Field only. Not compatible with the 91F, 131F, or other telescopes.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eConnection:\u003c\/strong\u003e Connects via the 111F’s photographic extension tube using the included M54×0.75 or M48×0.75 adapter rings. Both ends of the reducer body are M68×1 threads.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eBack focus:\u003c\/strong\u003e 55mm from the base of the M48×0.75 male thread. No additional spacing calculation required when using the supplied adapters.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eFilter compatibility:\u003c\/strong\u003e Built-in rear M48×0.75 thread accepts standard 2\" astronomy filters directly.\u003c\/p\u003e\n\n\u003ch2\u003eImportant Limitations\u003c\/h2\u003e\n\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003e111F only\u003c\/strong\u003e — this reducer is not compatible with the 91F, 131F, or any other telescope in the F Series.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eNot for visual observing\u003c\/strong\u003e — focal reducers are imaging-only accessories.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e55mm back focus must be respected\u003c\/strong\u003e — altering the back focus distance from 55mm will degrade corner star quality.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\n\n\u003cp\u003e\u003cstrong\u003eWhat does this reducer do to the 111F?\u003c\/strong\u003e\u003cbr\u003eIt reduces the focal length from 766mm to 566mm and the focal ratio from f\/6.9 to f\/5.1, giving a wider field of view and faster exposures.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eDoes it work on the 91F or 131F?\u003c\/strong\u003e\u003cbr\u003eNo. Each F Series telescope requires its own dedicated reducer. The 91F uses the 0.75× Reducer (M59 thread) and the 131F uses a different 0.74× Reducer (M72 thread).\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eDo I need a separate flattener at f\/5.1?\u003c\/strong\u003e\u003cbr\u003eNo. Field flattening is built into the reducer and covers the full 44mm image circle.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eWhat is the back focus distance?\u003c\/strong\u003e\u003cbr\u003e55mm from the base of the M48×0.75 male thread on the rear of the reducer.\u003c\/p\u003e\n\n\u003ch2\u003eOur Recommendation\u003c\/h2\u003e\n\n\u003cp\u003eAt Ontario Telescope and Accessories, we recommend the \u003cstrong\u003eAskar 111F 0.74× Reducer\u003c\/strong\u003e as a natural pairing for any 111F owner who regularly images large nebulae or works under light-polluted skies. The step from f\/6.9 to f\/5.1 is meaningful in practice — combined with the wider field, it transforms the 111F into a noticeably more capable wide-field imaging system. For 111F owners who haven’t yet added a reducer, this is the one accessory most likely to expand their imaging possibilities.\u003c\/p\u003e","brand":"Askar","offers":[{"title":"Default Title","offer_id":53154397028463,"sku":"111F-REDUCER-074X","price":418.6,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/1b1d4dbf-a360-4f29-a533-6f4e17a2feed.png?v=1779667504"},{"product_id":"askar-91f-0-75-focal-reducer","title":"Askar 91F 0.75× Focal Reducer","description":"\u003ch2\u003eAskar 91F 0.75× Focal Reducer — For the Askar 91F Flat-Field Astrograph\u003c\/h2\u003e\n\n\u003cp\u003eThe \u003cstrong\u003eAskar 91F 0.75× Reducer\u003c\/strong\u003e is a dedicated focal reducer designed exclusively for the Askar 91F Flat-Field astrograph. It reduces the 91F’s native f\/6.7 focal ratio down to f\/5, shortening the effective focal length from 609mm to 455mm. This delivers a noticeably wider field of view and a faster optical system that meaningfully reduces exposure times — particularly useful for large nebulae, wide star fields, and imaging from light-polluted locations.\u003c\/p\u003e\n\n\u003cp\u003eAlongside focal reduction, the reducer incorporates built-in field-flattening correction that eliminates field curvature across the full 44mm image circle. Stars are sharp and round from the centre to the corners of a full-frame sensor, with no additional flattener required at the reduced ratio.\u003c\/p\u003e\n\n\u003cp\u003eThe optical design uses a triplet lens group for smooth, well-corrected reduction. The standard back focus distance is 55mm from the M48×0.75 male thread. Both ends of the reducer body feature M59×1 threads. The 91F’s photographic extension tube connects directly via the included M54×0.75 and M48×0.75 adapter rings. The rear adapter ring has a built-in M48×0.75 standard 2\" filter thread for direct filter installation. The body is precision CNC-machined and ships with protective metal thread caps on both ends to guard against dust when not in use.\u003c\/p\u003e\n\n\u003ch2\u003eWho Is This Product Best For?\u003c\/h2\u003e\n\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eAskar 91F owners\u003c\/strong\u003e who want a wider field of view and faster exposures for large nebulae and star fields.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eImagers in light-polluted skies\u003c\/strong\u003e who benefit from the faster f\/5 ratio to shorten sub-exposure times.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eTravel astrophotographers\u003c\/strong\u003e already using the compact 91F who want to maximise field width on a lightweight setup.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eNarrowband and broadband filter users\u003c\/strong\u003e who want more imaging speed from the 91F system.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eUsers wanting flexibility\u003c\/strong\u003e between the native f\/6.7 (tighter framing, higher resolution) and f\/5 (wider field, faster) without a second telescope.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eWhy Choose the Askar 91F 0.75× Reducer?\u003c\/h2\u003e\n\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eDedicated design\u003c\/strong\u003e — optically optimized specifically for the 91F for consistent, well-corrected performance across the full 44mm image circle at f\/5.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eBuilt-in field flattening\u003c\/strong\u003e — one accessory handles both reduction and corner correction simultaneously.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eSignificantly faster system\u003c\/strong\u003e — f\/5 vs f\/6.7 means roughly 44% less exposure time required for the same signal.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eWider field\u003c\/strong\u003e — 455mm vs 609mm focal length gives approximately 25% more field width per axis.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eStandard 55mm back focus\u003c\/strong\u003e — no spacing guesswork; direct adapter connections are included.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFilter-ready rear thread\u003c\/strong\u003e — built-in M48×0.75 accepts standard 2\" astronomy filters directly.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eLightest F Series reducer\u003c\/strong\u003e — at just 0.3kg, adds virtually no weight penalty to the 91F travel setup.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eCNC body with protective caps\u003c\/strong\u003e — professional build quality with dust-proof metal end caps for storage and transport.\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 nebula and star cluster imaging with the Askar 91F\u003c\/li\u003e\n  \u003cli\u003eLarge emission and reflection nebulae (Orion, Rosette, Heart and Soul, etc.)\u003c\/li\u003e\n  \u003cli\u003eMilky Way core and wide star field imaging\u003c\/li\u003e\n  \u003cli\u003eNarrowband and broadband filter imaging from light-polluted sites\u003c\/li\u003e\n  \u003cli\u003ePortable and travel astrophotography setups\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eCompatibility and Accessory Notes\u003c\/h2\u003e\n\n\u003cp\u003e\u003cstrong\u003eCompatible telescope:\u003c\/strong\u003e Askar 91F Flat-Field only. Not compatible with the 111F, 131F, or any other telescope.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eConnection:\u003c\/strong\u003e Connects via the 91F’s photographic extension tube using the included M54×0.75 or M48×0.75 adapter rings. Both ends of the reducer body are M59×1 threads.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eBack focus:\u003c\/strong\u003e 55mm from the base of the M48×0.75 male thread. No additional spacing calculation required when using the supplied adapters.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eFilter compatibility:\u003c\/strong\u003e Built-in rear M48×0.75 thread accepts standard 2\" astronomy filters directly.\u003c\/p\u003e\n\n\u003ch2\u003eImportant Limitations\u003c\/h2\u003e\n\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003e91F only\u003c\/strong\u003e — not compatible with the 111F (which uses a 0.74× reducer with M68 threads) or the 131F (which uses a 0.74× reducer with M72 threads).\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eNot for visual observing\u003c\/strong\u003e — focal reducers are imaging-only accessories and are not used with eyepieces.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e55mm back focus must be respected\u003c\/strong\u003e — using additional spacers that alter the back focus from 55mm will degrade corner star quality.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\n\n\u003cp\u003e\u003cstrong\u003eWhat does this reducer do to the 91F?\u003c\/strong\u003e\u003cbr\u003eIt reduces the focal length from 609mm to 455mm and the focal ratio from f\/6.7 to f\/5, giving a wider field of view and faster exposures.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eDoes it work on the 111F or 131F?\u003c\/strong\u003e\u003cbr\u003eNo. Each F Series telescope has its own dedicated reducer with different thread sizes. The 111F uses a 0.74× Reducer (M68 thread) and the 131F uses a 0.74× Reducer (M72 thread).\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eDo I need a flattener at f\/5?\u003c\/strong\u003e\u003cbr\u003eNo. Field flattening is built into the reducer and covers the full 44mm image circle.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eWhat is the back focus?\u003c\/strong\u003e\u003cbr\u003e55mm from the base of the M48×0.75 male thread on the rear of the reducer.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eIs this suitable for a travel setup?\u003c\/strong\u003e\u003cbr\u003eYes. At 0.3kg it adds minimal weight and the compact size fits easily into any imaging kit bag.\u003c\/p\u003e\n\n\u003ch2\u003eOur Recommendation\u003c\/h2\u003e\n\n\u003cp\u003eAt Ontario Telescope and Accessories, we recommend the \u003cstrong\u003eAskar 91F 0.75× Reducer\u003c\/strong\u003e as an ideal companion for the 91F — particularly for imagers who primarily target large nebulae or who shoot from light-polluted sites where a faster focal ratio makes a real practical difference. At f\/5, the 91F system becomes one of the most capable and portable wide-field full-frame imaging setups available at this price point. For 91F owners who haven’t yet added a reducer, this is the single most impactful accessory purchase you can make for the telescope.\u003c\/p\u003e","brand":"Askar","offers":[{"title":"Default Title","offer_id":53154399125615,"sku":"91F-REDUCER-075X","price":278.6,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/697d8e02-5798-4712-9d20-77ec86f1ed18.png?v=1779667568"}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/collections\/1114d666-31b5-46c4-85c4-3c57ff6d48e7.png?v=1779734012","url":"https:\/\/ontariotelescope.com\/collections\/f-series.oembed","provider":"Ontario Telescope and Accessories","version":"1.0","type":"link"}