{"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","url":"https:\/\/ontariotelescope.com\/products\/askar-111f-0-74-focal-reducer","provider":"Ontario Telescope and Accessories","version":"1.0","type":"link"}