{"title":"Sky-Watcher Flatteners \u0026 Reducers","description":"\u003cp\u003eSky-Watcher Flatteners \u0026amp; Reducers. Part of \u003ca href=\"\/collections\/flatteners-and-reducers\"\u003eFlatteners, Reducers \u0026amp; Correctors\u003c\/a\u003e.\u003c\/p\u003e","products":[{"product_id":"skywatcher-reducer-corrector-85x-for-proed-evostar-80","title":"Skywatcher Reducer\/Corrector (.85x) for ProED \/ Evostar 80","description":"\u003cspan style=\"color: rgb(76, 81, 84); font-family: \" open sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003e0.85x Focal Reducer\/Corrector for Sky-Watcher PRO 80 ED APO is designed for serious Astro-Imagers. Optimized for the Sky-Watcher PRO 80 ED APO, this superb quality accessory effectively reduces the telescope’s focal length by a factor of 0.85x and provides much improved field-edge correction. Features:\u003c\/span\u003e\u003cul style=\"box-sizing: inherit; -webkit-font-smoothing: antialiased; text-size-adjust: none; -webkit-tap-highlight-color: rgba(0, 0, 0, 0); margin-top: 1rem; margin-bottom: 1rem; padding-left: 20px; color: rgb(76, 81, 84); font-family: \" open sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003e\n\u003cli style=\"box-sizing: inherit; -webkit-font-smoothing: antialiased; text-size-adjust: none; -webkit-tap-highlight-color: rgba(0, 0, 0, 0);\"\u003e55mm back focus\u003c\/li\u003e\n\u003cli style=\"box-sizing: inherit; -webkit-font-smoothing: antialiased; text-size-adjust: none; -webkit-tap-highlight-color: rgba(0, 0, 0, 0);\"\u003eM48 threads (not standard T-thread)\u003c\/li\u003e\n\u003cli style=\"box-sizing: inherit; -webkit-font-smoothing: antialiased; text-size-adjust: none; -webkit-tap-highlight-color: rgba(0, 0, 0, 0);\"\u003eDrops ProED 80 from f\/7.5 to f\/6.3\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Sky-Watcher","offers":[{"title":"Default Title","offer_id":44013473366127,"sku":"S20200","price":510.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/sky_watcher_s20200_focal_reducer_field_flattner_for_1060554_1800x1800__98122.jpg?v=1766554349"},{"product_id":"skywatcher-reducer-corrector-85x-for-proed-evostar-120","title":"Skywatcher Reducer\/Corrector (.85x) for ProED \/ Evostar 120","description":"\u003cspan style=\"color: rgb(76, 81, 84); font-family: \" open sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003e0.85x Focal Reducer\/Corrector for Sky-Watcher PRO 120 ED APO is designed for serious Astro-Imagers. Optimized for the Sky-Watcher PRO 120 ED APO, this superb quality accessory effectively reduces the telescope’s focal length by a factor of 0.85x and provides much improved field-edge correction. Features:\u003c\/span\u003e\u003cul style=\"box-sizing: inherit; -webkit-font-smoothing: antialiased; text-size-adjust: none; -webkit-tap-highlight-color: rgba(0, 0, 0, 0); margin-top: 1rem; margin-bottom: 1rem; padding-left: 20px; color: rgb(76, 81, 84); font-family: \" open sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003e\n\u003cli style=\"box-sizing: inherit; -webkit-font-smoothing: antialiased; text-size-adjust: none; -webkit-tap-highlight-color: rgba(0, 0, 0, 0);\"\u003e55mm back focus\u003c\/li\u003e\n\u003cli style=\"box-sizing: inherit; -webkit-font-smoothing: antialiased; text-size-adjust: none; -webkit-tap-highlight-color: rgba(0, 0, 0, 0);\"\u003eM48 threads (not standard T-thread)\u003c\/li\u003e\n\u003cli style=\"box-sizing: inherit; -webkit-font-smoothing: antialiased; text-size-adjust: none; -webkit-tap-highlight-color: rgba(0, 0, 0, 0);\"\u003eDrops ProED 120 from f\/7.5 to f\/6.3\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Sky-Watcher","offers":[{"title":"Default Title","offer_id":44013473398895,"sku":"S20202","price":550.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/reducercorrecto_large_120_1800x1800__67513.jpg?v=1766554356"},{"product_id":"skywatcher-reducer-corrector-85x-for-proed-evostar-100","title":"Skywatcher Reducer\/Corrector (.85x) for ProED \/ Evostar 100","description":"\u003cspan style=\"font-family: \" open sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003e0.85x Focal Reducer\/Corrector for Sky-Watcher PRO 100 ED APO is designed for serious Astro-Imagers. Optimized for the Sky-Watcher PRO 100 ED APO, this superb quality accessory effectively reduces the telescope’s focal length by a factor of 0.85x and provides much improved field-edge correction. Features:\u003c\/span\u003e\u003cul style=\"box-sizing: inherit; -webkit-font-smoothing: antialiased; text-size-adjust: none; -webkit-tap-highlight-color: rgba(0, 0, 0, 0); margin-top: 1rem; margin-bottom: 1rem; padding-left: 20px; font-family: \" open sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003e\n\u003cli style=\"box-sizing: inherit; -webkit-font-smoothing: antialiased; text-size-adjust: none; -webkit-tap-highlight-color: rgba(0, 0, 0, 0);\"\u003e55mm back focus\u003c\/li\u003e\n\u003cli style=\"box-sizing: inherit; -webkit-font-smoothing: antialiased; text-size-adjust: none; -webkit-tap-highlight-color: rgba(0, 0, 0, 0);\"\u003eM48 threads (not standard T-thread)\u003c\/li\u003e\n\u003cli style=\"box-sizing: inherit; -webkit-font-smoothing: antialiased; text-size-adjust: none; -webkit-tap-highlight-color: rgba(0, 0, 0, 0);\"\u003eDrops ProED 100 from f\/9 to f\/7.56\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Sky-Watcher","offers":[{"title":"Default Title","offer_id":44013473431663,"sku":"S20201","price":530.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/reducercorrecto_large_100_1800x1800__11765.jpg?v=1766554362"},{"product_id":"sky-watcher-quattro-coma-corrector","title":"Sky-Watcher Quattro Coma Corrector","description":"\u003cspan style=\"font-family: \" open sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003eDelivers stunning wide-field views with pinpoint stars to the edge of the field. Magnification remains unaltered.\u003c\/span\u003e","brand":"Sky-Watcher","offers":[{"title":"Default Title","offer_id":44013591330927,"sku":"S20204","price":680.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/s20204_quattrocomacorrector_1800x1800__44978.jpg?v=1766557202"},{"product_id":"field-flattener-for-evoguide-50","title":"Field Flattener for EvoGuide 50","description":"\u003cul data-mce-fragment=\"1\" style=\"box-sizing: inherit; -webkit-font-smoothing: antialiased; text-size-adjust: none; -webkit-tap-highlight-color: transparent; margin-top: 1rem; margin-bottom: 1rem; padding-left: 20px; font-size: 16px; background-color: rgb(255, 255, 255);\"\u003e\n\u003cli data-mce-fragment=\"1\" style=\"box-sizing: inherit; -webkit-font-smoothing: antialiased; text-size-adjust: none; -webkit-tap-highlight-color: transparent;\"\u003e\u003cspan style=\"font-family: Arial;\"\u003eCorrects for field curvature, allowing the Evoguide 50ED and 50DX to be used for astrophotography\u003c\/span\u003e\u003c\/li\u003e\n\u003cli data-mce-fragment=\"1\" style=\"box-sizing: inherit; -webkit-font-smoothing: antialiased; text-size-adjust: none; -webkit-tap-highlight-color: transparent;\"\u003e\u003cspan style=\"font-family: Arial;\"\u003eThread on metal caps\u003c\/span\u003e\u003c\/li\u003e\n\u003cli data-mce-fragment=\"1\" style=\"box-sizing: inherit; -webkit-font-smoothing: antialiased; text-size-adjust: none; -webkit-tap-highlight-color: transparent;\"\u003e\u003cspan style=\"font-family: Arial;\"\u003eT-thread connection or 1.25\" opening for camera mounting\u003c\/span\u003e\u003c\/li\u003e\n\u003cli data-mce-fragment=\"1\" style=\"box-sizing: inherit; -webkit-font-smoothing: antialiased; text-size-adjust: none; -webkit-tap-highlight-color: transparent;\"\u003e\u003cspan style=\"font-family: Arial;\"\u003e28mm imaging circle\u003c\/span\u003e\u003c\/li\u003e\n\u003cli data-mce-fragment=\"1\" style=\"box-sizing: inherit; -webkit-font-smoothing: antialiased; text-size-adjust: none; -webkit-tap-highlight-color: transparent;\"\u003e\u003cspan style=\"font-family: Arial;\"\u003e17.5mm back focus\u003c\/span\u003e\u003c\/li\u003e\n\u003cli data-mce-fragment=\"1\" style=\"box-sizing: inherit; -webkit-font-smoothing: antialiased; text-size-adjust: none; -webkit-tap-highlight-color: transparent;\"\u003e\u003cspan style=\"font-family: Arial;\"\u003e5.33 x 3.57-degree field of view when used with APS-C crop sensor \u003c\/span\u003e\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Sky-Watcher","offers":[{"title":"Default Title","offer_id":44013692092527,"sku":"S20214","price":160.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/S20214_Evo50_Flat_web_1800x1800__62760.jpg?v=1766559887"},{"product_id":"skywatcher-0-85x-reducer-flattener-for-evostar-72ed","title":"Skywatcher 0.85x Reducer\/Flattener for EvoStar 72ED","description":"\u003cul\u003e\n\u003cli\u003eCompatible with both APS-C and full frame sensors, APS-C (crop sensors) and smaller recommended\u003c\/li\u003e\n\u003cli\u003e55mm back focus\u003c\/li\u003e\n\u003cli\u003eDrops f\/ratio from native f\/5.8 (420mm) to f\/4.93 (355mm)\u003c\/li\u003e\n\u003cli\u003eReduces exposure time by 38% compared to native f\/5.8\u003c\/li\u003e\n\u003cli\u003e5.8 x 3.87-degree field of view when used with a full frame camera\u003c\/li\u003e\n\u003cli\u003e3.79 x 2.53-degree field of view when used with APS-C crop sensor \u003c\/li\u003e\n\u003cli\u003eIncludes thread-on adapter to mount reducer to Evostar 72ED focuser\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Sky-Watcher","offers":[{"title":"Default Title","offer_id":44013893582959,"sku":"S20212","price":580.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/S20212_Evostar72_Reducer_wIncludedAdapter2web_1800x1800__90537.jpg?v=1766565888"},{"product_id":"sky-watcher-esprit-100edx-field-flattener","title":"Sky-Watcher Esprit 100EDX Field Flattener","description":"\u003ch3\u003e\u003cstrong\u003eProduct Overview\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThe Esprit 100EDX Flattener is Sky-Watcher's dedicated field corrector for the Esprit 100EDX super apochromatic refractor. A fast triplet objective focuses onto a gently curved surface; a camera sensor is flat. The flattener resolves that mismatch, so stars hold their shape out to the frame edges instead of drawing short radial streaks in the corners while the centre of the frame stays sharp.\u003c\/p\u003e\n\u003cp\u003eSky-Watcher publishes a 44 mm corrected image circle for this corrector. That encloses the 43.3 mm diagonal of a full-frame sensor and covers APS-C with margin to spare, so framing choices are driven by focal length rather than by how much of the sensor the corrector reaches. On the Esprit 100EDX — published by Sky-Watcher as 100 mm aperture, 550 mm focal length, f\/5.5, FPL-53 triplet — that is a wide, fast field with corners that hold up.\u003c\/p\u003e\n\u003cp\u003eOne name to keep straight: this part is published for the \u003cstrong\u003eEsprit\u003c\/strong\u003e 100EDX, the super-apochromatic triplet. The \u003cstrong\u003eEvostar\u003c\/strong\u003e 100EDX doublet is served by a different corrector (S20216, which also covers the Esprit 70EDX).\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eWho It's For\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThis is the corrector Sky-Watcher pairs with the Esprit 100EDX, and it is the right part if you own that telescope and want flat, round stars across a large sensor at the scope's native focal length and ratio.\u003c\/p\u003e\n\u003cp\u003eIt suits deep-sky imagers working at the 100EDX's native 550 mm — large nebulae, open clusters, mid-size galaxy fields and mosaic panels — where the goal is a clean frame edge to edge rather than a shorter, faster field from a reducing corrector.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eKey Features \u0026amp; Design\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eMatched to the Esprit 100EDX:\u003c\/strong\u003e Sky-Watcher publishes compatibility with the Esprit 100EDX specifically. The correction is computed for that objective rather than sold as a universal flattener.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e44 mm corrected image circle:\u003c\/strong\u003e the published figure covers a full-frame sensor's 43.3 mm diagonal and leaves APS-C well inside the corrected zone.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFlattening only:\u003c\/strong\u003e Sky-Watcher publishes no reduction factor for this corrector, so the telescope's native 550 mm and f\/5.5 carry through it.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSingle-piece corrector:\u003c\/strong\u003e one optic in the imaging train between focuser and camera, with no separate elements to align.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eOptical \/ Mechanical Design\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eWhat it corrects:\u003c\/strong\u003e field curvature across the imaging field of the Esprit 100EDX. The visible symptom it removes is corner stars that elongate radially, pointing away from the frame centre, while the middle of the frame focuses cleanly.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCorrected image circle:\u003c\/strong\u003e 44 mm, as published by Sky-Watcher. Sensor coverage follows directly from that number — a full-frame sensor measures 43.3 mm corner to corner and an APS-C sensor roughly 28 mm, so both sit inside the corrected field.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eResulting focal length and focal ratio:\u003c\/strong\u003e Sky-Watcher publishes no reduction factor and no altered figures, consistent with a flattener that works at native focal length. The Esprit 100EDX's published 550 mm and f\/5.5 are what you image at with this part in the train. At 550 mm across a 44 mm circle, a full-frame sensor takes in roughly three and a half degrees on the long axis, which is why this pairing suits large targets and mosaic work.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eRequired backfocus and thread interface:\u003c\/strong\u003e Sky-Watcher does not publish a backfocus distance in millimetres or a thread size for this corrector on its product page, and no manual or datasheet is linked there. Those two numbers determine how the corrector spaces to your sensor, and corner star shape is what depends on getting the spacing right. Send us your camera, filter drawer or filter wheel and any adapters and we will lay the train out with you before you order.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eRecommended Uses\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eDeep-sky astrophotography at native focal length:\u003c\/strong\u003e large emission nebulae, open clusters, mid-size galaxy fields and star fields at 550 mm.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLarge-sensor imaging:\u003c\/strong\u003e the 44 mm circle supports full-frame and APS-C cameras, including cooled astronomical CMOS bodies in those formats.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMosaic panels:\u003c\/strong\u003e flat corners let adjacent panels blend without a ring of distorted stars at every seam.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNarrowband and broadband alike:\u003c\/strong\u003e field curvature is a geometric error, so the correction applies regardless of the filter in front of the sensor.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eCompatibility and Accessory Notes\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eSky-Watcher lists one compatible telescope: the Esprit 100EDX. Their EDX correctors are published tube by tube — S20216 covers the Esprit 70EDX and the Evostar 100EDX, S20218 the Esprit 120EDX, S20219 the Esprit 150EDX — and refractors from other makers pair with their own. Tell us the exact model printed on your tube and we will confirm which corrector belongs on it.\u003c\/p\u003e\n\u003cp\u003eThe vendor does not publish the thread interface or the spacing distance to the sensor, so the adapters between this corrector and your camera cannot be specified from published data. Send us your camera model, filter wheel or drawer, and any off-axis guider in the train, and we will map the imaging train and tell you exactly what sits between the two.\u003c\/p\u003e\n\u003cp\u003eNothing about this part changes the mount side of the setup: it adds a short optic and roughly a pound behind the focuser rather than changing how the telescope mounts.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eGood to Know Before You Order\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eBackfocus is not published.\u003c\/strong\u003e Sky-Watcher gives no spacing figure in millimetres for this corrector. Corner star shape depends on hitting the correct sensor distance, and we can work that out with you from your specific camera and adapters.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eThread interface is not published.\u003c\/strong\u003e No thread size appears on the vendor page, so the camera-side connection is confirmed case by case rather than assumed.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEsprit 100EDX, not Evostar 100EDX.\u003c\/strong\u003e The two share a 100 mm aperture and a similar name but take different correctors; the Evostar doublet is covered by S20216.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIt is a flattener, not a reducer.\u003c\/strong\u003e No reduction factor is published, so focal length and focal ratio stay at the telescope's native values.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBox contents are not published.\u003c\/strong\u003e The vendor states no spacer, adapter or case as supplied with the corrector.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWeight figure is the vendor's shipping weight.\u003c\/strong\u003e Sky-Watcher lists 1.0 lb for this item and publishes no separate optic-only mass in a specification table.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eVendor image note.\u003c\/strong\u003e Sky-Watcher states \"Images subject to change\" on this listing, which is normal for a recently released part.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eFrequently Asked Questions\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eIs it difficult to set up?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003ePhysically it is one optic that goes into the imaging train between the focuser and the camera, and it stays there. The part that takes attention is the spacing to the sensor, which Sky-Watcher does not publish for this corrector. Send us the camera and adapters you plan to use and we will lay out the train for you.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDoes it change the focal length or focal ratio?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eSky-Watcher publishes no reduction factor, resulting focal length, or resulting focal ratio for this corrector. It flattens the field at the telescope's native 550 mm and f\/5.5.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWill it cover my full-frame camera?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe published corrected image circle is 44 mm and a full-frame sensor measures 43.3 mm across the diagonal, so the sensor sits inside the corrected field. APS-C sits well inside it.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eI have an Evostar 100EDX — is this the one?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eNo. The Evostar 100EDX doublet is published against S20216, the corrector shared with the Esprit 70EDX. This part is published for the Esprit 100EDX triplet. Send us the model printed on your tube and we will match it.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDoes it fit the earlier Esprit 100ED?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eSky-Watcher publishes compatibility only with the Esprit 100EDX for this part. Earlier Esprit models have their own correctors in the range. Send us the model on your tube and we will confirm which one applies.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat weight does it add to the imaging train?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eSky-Watcher lists 1.0 lb for this item. It is a small addition behind the focuser next to the camera, filters and any guider.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eA dedicated flattener for the Esprit 100EDX with a published 44 mm corrected circle — enough to keep stars round across a full-frame sensor at the telescope's native 550 mm and f\/5.5. Sky-Watcher leaves the backfocus and thread figures unpublished, so we confirm the spacing with you against your own camera and adapters and send it out ready to drop into the train.\u003c\/p\u003e","brand":"Sky-Watcher","offers":[{"title":"Default Title","offer_id":53896756691055,"sku":"S20217","price":330.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/100_2.jpg?v=1785253569"},{"product_id":"sky-watcher-esprit-120edx-field-flattener","title":"Sky-Watcher Esprit 120EDX Field Flattener","description":"\u003ch3\u003e\u003cstrong\u003eProduct Overview\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThe Esprit 120EDX Flattener is Sky-Watcher's dedicated field corrector for the Esprit 120EDX super apochromatic refractor. A fast triplet objective focuses onto a gently curved surface; a camera sensor is flat. The flattener resolves that mismatch so stars hold their shape out to the frame edges instead of drawing short radial streaks in the corners while the centre stays sharp.\u003c\/p\u003e\n\u003cp\u003eSky-Watcher publishes a 44 mm corrected image circle for this corrector. That encloses the 43.3 mm diagonal of a full-frame sensor and covers APS-C with margin to spare, so framing choices are driven by focal length rather than by how much of the sensor the corrector reaches.\u003c\/p\u003e\n\u003cp\u003eThis is a flattener, not a reducer. Sky-Watcher publishes no reduction factor and no altered focal length or focal ratio for it, so the Esprit 120EDX images at its native figures with this part in the train. The 0.77x Reducer\/Flattener for the Esprit 120 (S20209) is a separate optic with a different prescription.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eWho It's For\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThis is the corrector Sky-Watcher pairs with the Esprit 120EDX, and it is the right part if you own that telescope and want flat, round stars across a large sensor at the scope's native focal length \u0026amp; ratio.\u003c\/p\u003e\n\u003cp\u003eIt suits deep-sky imagers who want the full native image scale — galaxies, globular clusters, planetary nebulae, small to mid-size emission targets — rather than the wider, faster field a reducing corrector produces. If your priority is shorter exposures and a wider frame, the 0.77x reducer\/flattener for the Esprit line is the part built for that job.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eKey Features \u0026amp; Design\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eMatched to the Esprit 120EDX:\u003c\/strong\u003e Sky-Watcher publishes compatibility with the Esprit 120EDX specifically. The correction is computed for that objective rather than sold as a universal flattener.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e44 mm corrected image circle:\u003c\/strong\u003e the published figure covers a full-frame sensor's 43.3 mm diagonal and leaves APS-C well inside the corrected zone.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFlattening only:\u003c\/strong\u003e no published reduction factor, so the telescope's native focal length and focal ratio carry through the corrector.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSingle-piece corrector:\u003c\/strong\u003e one optic in the imaging train between focuser and camera, with no separate elements to align.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eOptical \/ Mechanical Design\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eWhat it corrects:\u003c\/strong\u003e field curvature across the imaging field of the Esprit 120EDX. The visible symptom it removes is corner stars that elongate radially, pointing away from the frame centre, while the middle of the frame focuses cleanly.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCorrected image circle:\u003c\/strong\u003e 44 mm, as published by Sky-Watcher. Sensor coverage follows directly from that number — a full-frame sensor measures 43.3 mm corner to corner and an APS-C sensor roughly 28 mm, so both sit inside the corrected field.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eResulting focal length and focal ratio:\u003c\/strong\u003e Sky-Watcher publishes none, consistent with a flattener that works at native focal length. We publish only what they publish, so no altered figures appear here.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eRequired backfocus and thread interface:\u003c\/strong\u003e Sky-Watcher does not publish a backfocus distance in millimetres or a thread size for this corrector on its product page, and no manual or datasheet is linked there. Those two numbers determine how the corrector spaces to your camera, so send us your camera, filter drawer and any adapters and we will work the train out with you before you order.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eRecommended Uses\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eDeep-sky astrophotography at native focal length:\u003c\/strong\u003e galaxies, globular clusters, planetary nebulae and compact emission regions where image scale matters more than field width.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLarge-sensor imaging:\u003c\/strong\u003e the 44 mm circle supports full-frame and APS-C cameras, including cooled astronomical CMOS bodies in those formats.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMosaic panels:\u003c\/strong\u003e flat corners let adjacent panels blend without a ring of distorted stars at every seam.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNarrowband and broadband alike:\u003c\/strong\u003e field curvature is a geometric error, so the correction applies regardless of the filter in front of the sensor.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eCompatibility and Accessory Notes\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eSky-Watcher lists one compatible telescope: the Esprit 120EDX. Other Esprit models — including the earlier Esprit 120ED — have their own correctors in Sky-Watcher's range, and refractors from other makers pair with their own. Tell us the exact model on your tube and we will confirm which corrector belongs on it.\u003c\/p\u003e\n\u003cp\u003eThe vendor does not publish the thread interface or the spacing distance to the sensor, so the adapters between this corrector and your camera cannot be specified from published data. Send us your camera model, filter wheel or drawer, and any off-axis guider in the train, and we will map the imaging train and tell you exactly what sits between the two.\u003c\/p\u003e\n\u003cp\u003eNothing about this part changes the mount side of the setup: it adds a short optic and roughly a pound behind the focuser rather than changing how the telescope mounts.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eGood to Know Before You Order\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eBackfocus is not published.\u003c\/strong\u003e Sky-Watcher gives no spacing figure in millimetres for this corrector. Corner star shape depends on hitting the correct sensor distance, and we can work that out with you from your specific camera and adapters.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eThread interface is not published.\u003c\/strong\u003e No thread size appears on the vendor page, so the camera-side connection is confirmed case by case rather than assumed.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePublished for the Esprit 120EDX.\u003c\/strong\u003e The 44 mm figure is stated for that telescope and is not carried across to other models.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIt is a flattener, not a reducer.\u003c\/strong\u003e Focal length and focal ratio stay at the telescope's native values; the separate 0.77x reducer\/flattener is the part that changes them.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWeight figure is the vendor's shipping weight.\u003c\/strong\u003e Sky-Watcher lists 1.0 lb for this item and publishes no separate optic-only mass in a specification table.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eVendor image note.\u003c\/strong\u003e Sky-Watcher states \"Images subject to change\" on this listing, which is normal for a recently released part.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eFrequently Asked Questions\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eIs it difficult to set up?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003ePhysically it is one optic that goes into the imaging train between the focuser and the camera, and it stays there. The part that takes attention is the spacing to the sensor, which Sky-Watcher does not publish for this corrector. Send us the camera and adapters you plan to use and we will lay out the train for you.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDoes it change the focal length or focal ratio?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eSky-Watcher publishes no reduction factor, resulting focal length, or resulting focal ratio for this corrector. It flattens the field at the telescope's native figures. The 0.77x Reducer\/Flattener is the part that shortens focal length and speeds the ratio.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWill it cover my full-frame camera?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe published corrected image circle is 44 mm and a full-frame sensor measures 43.3 mm across the diagonal, so the sensor sits inside the corrected field. APS-C sits well inside it.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDoes it fit the Esprit 120ED rather than the 120EDX?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eSky-Watcher publishes compatibility only with the Esprit 120EDX for this part. The Esprit 120ED has its own correctors in the range, including a 0.77x reducer\/flattener. Send us the model printed on your tube and we will match it.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat weight does it add to the imaging train?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eSky-Watcher lists 1.0 lb for this item. It is a small addition behind the focuser next to the camera, filters and any guider.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eA dedicated flattener for the Esprit 120EDX with a published 44 mm corrected circle — enough to keep stars round across a full-frame sensor at the telescope's native focal length. Sky-Watcher leaves the backfocus and thread figures unpublished, so we confirm the spacing with you against your own camera and adapters and send it out ready to drop into the train.\u003c\/p\u003e","brand":"Sky-Watcher","offers":[{"title":"Default Title","offer_id":53896761639023,"sku":"S20218","price":440.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/120FieldCorrector_2_5fc66d00-f553-4b84-8181-6c6d16fc7c32.jpg?v=1785253650"},{"product_id":"sky-watcher-esprit-150edx-field-flattener","title":"Sky-Watcher Esprit 150EDX Field Flattener","description":"\u003ch3\u003e\u003cstrong\u003eProduct Overview\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThe Esprit 150EDX Flattener is Sky-Watcher's dedicated field corrector for the Esprit 150EDX super apochromatic refractor. The objective brings light to focus on a slightly curved surface while a camera sensor is flat, and that difference is what turns corner stars into short radial streaks while the centre of the frame is pinpoint. This corrector sits in the imaging train and flattens the focal surface onto the sensor plane.\u003c\/p\u003e\n\u003cp\u003eSky-Watcher publishes a 44 mm corrected image circle for it. A full-frame sensor measures 43.3 mm across the diagonal, so the corrected field encloses full-frame and leaves an APS-C sensor comfortably inside it.\u003c\/p\u003e\n\u003cp\u003eThis part flattens; it does not reduce. Sky-Watcher publishes no reduction factor, no altered focal length and no altered focal ratio for it, so the Esprit 150EDX images at its native figures with this corrector in place. The 0.77x Reducer\/Flattener for the Esprit 150 (S20215) is a separate optic built for the opposite job.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eWho It's For\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThis is the corrector Sky-Watcher pairs with the Esprit 150EDX, so it is the right part if you own that telescope and want flat, round stars across a large sensor at the scope's native focal length \u0026amp; ratio.\u003c\/p\u003e\n\u003cp\u003eThe Esprit 150 is the longest tube in the line, and the reason to flatten rather than reduce is image scale: galaxy detail, globular cluster cores, planetary nebulae and small emission knots all benefit from keeping every millimetre of native focal length. If a wider, faster field is what you are after instead, the 0.77x reducer\/flattener for the Esprit 150 is the part built for that.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eKey Features \u0026amp; Design\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eMatched to the Esprit 150EDX:\u003c\/strong\u003e Sky-Watcher publishes compatibility with the Esprit 150EDX specifically, so the correction is figured for that objective rather than sold as a universal flattener.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e44 mm corrected image circle:\u003c\/strong\u003e covers a full-frame sensor's 43.3 mm diagonal and places APS-C well inside the corrected zone.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFlattening only:\u003c\/strong\u003e with no published reduction factor, the telescope's native focal length and focal ratio carry straight through.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSingle optic in the train:\u003c\/strong\u003e one corrector between focuser and camera, with no separate elements to align against each other.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eOptical \/ Mechanical Design\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eWhat it corrects:\u003c\/strong\u003e field curvature across the Esprit 150EDX imaging field. The symptom it removes is radial elongation of stars toward the frame corners while the centre focuses cleanly.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCorrected image circle:\u003c\/strong\u003e 44 mm, as published by Sky-Watcher. Sensor coverage follows from that figure — full-frame spans 43.3 mm corner to corner and APS-C roughly 28 mm, so both fall inside the corrected field.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eResulting focal length and focal ratio:\u003c\/strong\u003e Sky-Watcher publishes neither, which is consistent with a flattener that works at native focal length. Only published figures appear here, so no altered numbers are given.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eRequired backfocus and thread interface:\u003c\/strong\u003e the vendor product page carries no backfocus distance in millimetres and no thread size, and links no manual or datasheet. Those two figures set how the corrector spaces to the sensor, so send us your camera, filter drawer or wheel and any adapters and we will work the spacing out with you.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eRecommended Uses\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eDeep-sky astrophotography at native focal length:\u003c\/strong\u003e galaxies, globular clusters, planetary nebulae and compact nebular detail, where the Esprit 150's image scale is the point.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLarge-sensor imaging:\u003c\/strong\u003e the 44 mm circle supports full-frame and APS-C cameras, including cooled astronomical CMOS bodies in those formats.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMosaics:\u003c\/strong\u003e flat corners let adjacent panels stitch without a ring of distorted stars at each seam.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNarrowband and broadband:\u003c\/strong\u003e field curvature is geometric, so the correction holds whatever filter is in front of the sensor.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eCompatibility and Accessory Notes\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eSky-Watcher lists one compatible telescope for this corrector: the Esprit 150EDX. The earlier Esprit 150ED and the other tubes in the range have their own correctors, and refractors from other makers pair with theirs. Send us the exact model printed on your tube and we will confirm which corrector belongs on it.\u003c\/p\u003e\n\u003cp\u003eBecause the thread interface and sensor spacing are not published, the adapter stack between this corrector and your camera cannot be specified from vendor data alone. Tell us your camera model, filter wheel or drawer, and any off-axis guider, and we will map the imaging train and tell you exactly what sits where.\u003c\/p\u003e\n\u003cp\u003eOn the mount side nothing changes: this adds a short optic and roughly a pound behind the focuser rather than altering how the telescope rides.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eGood to Know Before You Order\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eBackfocus is not published.\u003c\/strong\u003e Sky-Watcher gives no spacing figure in millimetres for this corrector. Corner star shape depends on hitting the correct sensor distance, and we can work that out with you from your camera and adapters.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eThread interface is not published.\u003c\/strong\u003e No thread size appears on the vendor page, so the camera-side connection is confirmed case by case.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePublished for the Esprit 150EDX.\u003c\/strong\u003e The 44 mm figure is stated for that telescope and is not carried across to other models.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIt is a flattener, not a reducer.\u003c\/strong\u003e Focal length and focal ratio stay at the telescope's native values; the separate 0.77x reducer\/flattener is the part that changes them.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWeight figure is the vendor's shipping weight.\u003c\/strong\u003e Sky-Watcher lists 1.0 lb for this item and publishes no separate optic-only mass in a specification table.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eVendor image note.\u003c\/strong\u003e Sky-Watcher states \"Images subject to change\" on this listing, which is usual for a recently released part.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eFrequently Asked Questions\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eIs it difficult to set up?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eIt is one optic that installs between the focuser and the camera and then stays there. The element that takes attention is the spacing to the sensor, which Sky-Watcher does not publish for this corrector. Send us the camera and adapters you plan to use and we will lay the train out for you.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDoes it change the focal length or focal ratio?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eSky-Watcher publishes no reduction factor, resulting focal length or resulting focal ratio for it. It flattens the field at the telescope's native figures. The 0.77x Reducer\/Flattener is the part that shortens focal length and speeds the ratio.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWill it cover my full-frame camera?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe published corrected image circle is 44 mm and a full-frame sensor measures 43.3 mm on the diagonal, so the sensor sits inside the corrected field. APS-C sits well inside it.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDoes it fit the Esprit 150ED rather than the 150EDX?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eSky-Watcher publishes compatibility only with the Esprit 150EDX for this part. The Esprit 150ED has its own correctors in the range, including a 0.77x reducer\/flattener. Send us the model on your tube and we will match it.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eHow much does it add to the imaging train?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eSky-Watcher lists 1.0 lb for this item — a small addition behind the focuser alongside the camera, filters and any guider.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThe dedicated flattener for the Esprit 150EDX, with a published 44 mm corrected circle that keeps stars round across a full-frame sensor at the telescope's native focal length. Sky-Watcher leaves backfocus and thread figures unpublished, so we confirm the spacing against your own camera and adapters and send it out ready to drop into the train.\u003c\/p\u003e","brand":"Sky-Watcher","offers":[{"title":"Default Title","offer_id":53896765112431,"sku":"S20219","price":550.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/150_2.jpg?v=1785253731"},{"product_id":"sky-watcher-0-77x-reducer-flattener-for-esprit-120ed","title":"Sky-Watcher 0.77x Reducer\/Flattener for Esprit 120ED","description":"\u003ch3\u003e\u003cstrong\u003eProduct Overview\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThe Esprit 120ED Reducer\/Flattener is Sky-Watcher's 0.77x corrector for the Esprit 120ED. It does two jobs in one optic: it flattens the curved focal surface the triplet objective produces so corner stars stay round, and it shortens the system. Sky-Watcher publishes the change as a drop from native f\/7 (840mm) to f\/5.4 (647mm).\u003c\/p\u003e\n\u003cp\u003eThat faster ratio is the reason most people fit one. Sky-Watcher publishes a 68% reduction in exposure time compared with native f\/7 — the same signal arrives in a fraction of the integration, which shows up as more usable subs per night rather than as a change in what the telescope can resolve.\u003c\/p\u003e\n\u003cp\u003eThe field grows with it. Sky-Watcher publishes a 3.18 x 2.12-degree field of view on a full-frame camera and 2.08 x 1.39 degrees on an APS-C crop sensor, with a 34 mm fully illuminated field that the vendor states can handle full frame as well.\u003c\/p\u003e\n\u003cp\u003eThis is the reducing corrector for the Esprit 120ED. The Esprit 120EDX Flattener (S20218) is a different part — it flattens at native focal length and publishes no reduction.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eWho It's For\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThis is for Esprit 120ED owners imaging wide targets: large emission nebulae, open clusters with surrounding nebulosity, star fields, and anything that runs off the edge of the frame at 840 mm. At 647 mm and f\/5.4 the same telescope frames a noticeably wider field and gathers it faster.\u003c\/p\u003e\n\u003cp\u003eIt also suits anyone working from a site with limited clear time or heavy light pollution, where the 68% shorter exposure Sky-Watcher publishes translates directly into finishing a target in fewer nights.\u003c\/p\u003e\n\u003cp\u003eIf the goal is maximum image scale on small targets instead — galaxies, globulars, planetary nebulae — a plain flattener at native focal length is the part that serves that.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eKey Features \u0026amp; Design\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e0.77x reduction, published end to end:\u003c\/strong\u003e Sky-Watcher states the result as f\/7 (840mm) dropping to f\/5.4 (647mm) on the Esprit 120ED, so the working figures are the vendor's own rather than an estimate.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eReducer and flattener in one optic:\u003c\/strong\u003e field curvature correction and focal reduction happen in the same unit, so only one element joins the imaging train.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e34 mm fully illuminated field:\u003c\/strong\u003e the vendor's published figure, with the note that it can handle full frame as well.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTwo backfocus configurations:\u003c\/strong\u003e 95 mm back-focus as supplied, or 55 mm with the back focus spacer and M48 ring installed — the 55 mm figure is the standard astro-camera spacing.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBuilt-in 2\" filter cell:\u003c\/strong\u003e a 2-inch filter threads into the corrector itself, putting the filter in the light path without a separate drawer or spacer stack.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePublished fields of view:\u003c\/strong\u003e 3.18 x 2.12 degrees on full frame, 2.08 x 1.39 degrees on APS-C.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eOptical \/ Mechanical Design\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eWhat it corrects:\u003c\/strong\u003e field curvature across the Esprit 120ED imaging field, combined with a 0.77x focal reduction. Without a corrector, stars in the corners stretch radially while the frame centre focuses cleanly; this optic flattens that surface onto the sensor plane and shortens the system at the same time.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eResulting focal length and focal ratio:\u003c\/strong\u003e Sky-Watcher publishes the change as native f\/7 (840mm) to f\/5.4 (647mm). Both figures are the vendor's, stated for the Esprit 120ED specifically.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCorrected image circle:\u003c\/strong\u003e 34 mm fully illuminated, with Sky-Watcher noting it can handle full frame as well. A full-frame sensor's 43.3 mm diagonal sits outside the 34 mm fully illuminated circle, so the far corners of a full-frame chip fall in the region the vendor describes as usable rather than fully illuminated; an APS-C sensor at roughly 28 mm diagonal sits entirely inside it. The published fields of view follow from that — 3.18 x 2.12 degrees full frame, 2.08 x 1.39 degrees APS-C.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eRequired backfocus:\u003c\/strong\u003e 95 mm as supplied, or 55 mm when the back focus spacer and M48 ring are installed. 55 mm is the distance most cooled astronomical cameras and filter wheels are built around, so the reconfigured setting is the one most imaging trains land on.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eThread interface:\u003c\/strong\u003e M48, by way of the M48 ring that pairs with the 55 mm back focus configuration.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eFilter mounting:\u003c\/strong\u003e the 2\" filter cell is built into the corrector, so a 2-inch filter sits inside the reduced light path rather than adding length to the train.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eRecommended Uses\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eWide-field deep-sky astrophotography:\u003c\/strong\u003e large emission and reflection nebulae, cluster-plus-nebulosity fields and Milky Way regions that overflow the native 840 mm frame.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eShort-session and light-polluted imaging:\u003c\/strong\u003e the published 68% exposure reduction against native f\/7 puts more finished data into each clear night.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNarrowband work:\u003c\/strong\u003e the faster ratio offsets the transmission cost of narrow filters, and the built-in 2\" cell holds the filter in the light path.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAPS-C and full-frame imaging:\u003c\/strong\u003e APS-C sits inside the 34 mm fully illuminated field; full frame is covered by the vendor's stated capability with the published 3.18 x 2.12-degree frame.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eCompatibility and Accessory Notes\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eSky-Watcher publishes this corrector for the Esprit 120ED, and the reduction figures — f\/7 (840mm) to f\/5.4 (647mm) — are stated for that telescope. Other Esprit models pair with their own correctors, including the separate Esprit 120EDX Flattener, and refractors from other makers have their own. Send us the exact model printed on your tube and we will confirm which corrector belongs on it.\u003c\/p\u003e\n\u003cp\u003eThe two published backfocus settings shape the rest of the train. At 55 mm, with the back focus spacer and M48 ring installed, the corrector meets the standard most cooled astro cameras and filter wheels are dimensioned for. At 95 mm as supplied, the extra distance has to be filled by whatever sits between corrector and sensor. Send us your camera, filter wheel or drawer, off-axis guider and any adapters, and we will add the train up with you and confirm which configuration your setup wants.\u003c\/p\u003e\n\u003cp\u003eFilters thread into the built-in 2\" cell, so a 2-inch filter needs no separate drawer. Cameras with their own internal filter wheel simply leave that cell empty.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eGood to Know Before You Order\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eThe published figures are for the Esprit 120ED.\u003c\/strong\u003e 840mm to 647mm and f\/7 to f\/5.4 are stated for that telescope. Other refractors reduce by their own numbers with their own correctors.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBackfocus decides corner star shape.\u003c\/strong\u003e The corrector delivers 95 mm as supplied and 55 mm with the back focus spacer and M48 ring installed; the imaging train is built to whichever of those two figures you use.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e34 mm is the fully illuminated field.\u003c\/strong\u003e Sky-Watcher states it can handle full frame as well, so a full-frame sensor's outer corners lie beyond the fully illuminated circle in the region the vendor describes as usable.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFilter cell takes 2-inch filters.\u003c\/strong\u003e The built-in cell is sized for 2\" filters; other filter sizes go elsewhere in the train.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eThis is the reducing corrector, not the flattener.\u003c\/strong\u003e The Esprit 120EDX Flattener is a separate part that works at native focal length.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eVendor publishes no barcode for this SKU.\u003c\/strong\u003e The UPC we carry is 050234202091.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eVendor lists 2.0 lb for this item.\u003c\/strong\u003e That is the published weight; no separate optic-only mass appears in a specification table.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eFrequently Asked Questions\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eIs it difficult to set up?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe optic threads into the imaging train once and stays there. The decision that matters is which backfocus you build to — 95 mm as supplied, or 55 mm with the back focus spacer and M48 ring installed — and then adding the camera, filter wheel and adapters up to that number. Send us your components and we will do that arithmetic with you.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat focal length and focal ratio do I end up with?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eSky-Watcher publishes the Esprit 120ED as dropping from native f\/7 (840mm) to f\/5.4 (647mm) with this reducer\/flattener fitted.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eHow much faster is it in practice?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eSky-Watcher publishes a 68% reduction in exposure time compared with native f\/7 for the same result.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWill it cover a full-frame sensor?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eSky-Watcher publishes a 34 mm fully illuminated field and states it can handle full frame as well, quoting a 3.18 x 2.12-degree field of view on a full-frame camera and 2.08 x 1.39 degrees on APS-C.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat thread does it use?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eM48, via the M48 ring that goes with the 55 mm back focus configuration.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCan I use filters with it?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eYes — there is a built-in 2\" filter cell for mounting filters, so a 2-inch filter sits in the light path without a separate drawer.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eSky-Watcher's own 0.77x corrector for the Esprit 120ED: f\/7 (840mm) becomes f\/5.4 (647mm), exposure time drops by a published 68%, the field opens to 3.18 x 2.12 degrees on full frame, and a 2\" filter threads straight into the corrector. Tell us what camera and filters you are running and we will confirm the 55 mm or 95 mm spacing with you before it ships.\u003c\/p\u003e","brand":"Sky-Watcher","offers":[{"title":"Default Title","offer_id":53896771436655,"sku":"S20209","price":730.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/S20209_Esprit120_RedFlat_web.jpg?v=1785253815"},{"product_id":"sky-watcher-0-77x-reducer-flattener-for-esprit-150ed","title":"Sky-Watcher 0.77x Reducer\/Flattener for Esprit 150ED","description":"\u003ch3\u003e\u003cstrong\u003eProduct Overview\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThe Esprit 150ED Reducer\/Flattener is Sky-Watcher's 0.77x corrector for the Esprit 150ED. It flattens the curved focal surface the triplet objective produces, so stars stay round out to the corners, and shortens the system at the same time. Sky-Watcher publishes the change as a drop from native f\/7 (1050mm) to f\/5.4 (810mm).\u003c\/p\u003e\n\u003cp\u003eOn the largest tube in the Esprit line, that shift matters most in time. Sky-Watcher publishes a 68% reduction in exposure time compared with native f\/7 — a 1050 mm f\/7 system is a demanding place to collect photons, and f\/5.4 turns the same target into a materially shorter project.\u003c\/p\u003e\n\u003cp\u003eThe frame widens with the reduction. Sky-Watcher publishes a 2.54 x 1.7-degree field of view on a full-frame camera and 1.66 x 1.11 degrees on APS-C, backed by a 36 mm fully illuminated field the vendor states is compatible with both APS-C and full frame sensors.\u003c\/p\u003e\n\u003cp\u003eThis is the reducing corrector for the Esprit 150ED. The Esprit 150EDX Flattener (S20219) is a separate part that flattens at native focal length and publishes no reduction.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eWho It's For\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThis is for Esprit 150ED owners who want the tube's aperture without its native 1050 mm framing — large emission nebulae, extended cluster fields, bright galaxy groups, anything that crowds the edges at f\/7. At 810 mm and f\/5.4 the same telescope covers 2.54 x 1.7 degrees on a full-frame sensor.\u003c\/p\u003e\n\u003cp\u003eIt also fits anyone whose clear nights are the scarce resource. The published 68% exposure reduction against native f\/7 is the difference between finishing a narrowband target over a season and finishing it over a few weeks.\u003c\/p\u003e\n\u003cp\u003eIf maximum image scale on small targets is the aim instead, a flattener working at the native 1050 mm is the part for that.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eKey Features \u0026amp; Design\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e0.77x reduction, published end to end:\u003c\/strong\u003e Sky-Watcher states the result as f\/7 (1050mm) dropping to f\/5.4 (810mm) on the Esprit 150ED, so both working figures come from the vendor.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eReducer and flattener in one optic:\u003c\/strong\u003e curvature correction and focal reduction in a single unit, adding one element to the imaging train.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e36 mm fully illuminated field:\u003c\/strong\u003e Sky-Watcher's published figure, stated as compatible with both APS-C and full frame sensors.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTwo backfocus configurations:\u003c\/strong\u003e 90 mm back-focus as supplied, or 55 mm with the back focus spacer and M48 ring installed — 55 mm being the spacing most cooled astro cameras are built around.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBuilt-in 2\" filter cell:\u003c\/strong\u003e a 2-inch filter mounts into the light path inside the corrector rather than in a separate drawer.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eComplete in the box:\u003c\/strong\u003e Sky-Watcher lists the reducer, metal thread-on caps, back focus spacer and M48 thread adapter as included.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eOptical \/ Mechanical Design\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eWhat it corrects:\u003c\/strong\u003e field curvature across the Esprit 150ED imaging field, combined with a 0.77x focal reduction. Uncorrected, the corners of a large sensor show stars stretched radially while the frame centre is sharp; this optic flattens that surface onto the sensor plane and shortens the system in the same pass.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eResulting focal length and focal ratio:\u003c\/strong\u003e Sky-Watcher publishes the change as native f\/7 (1050mm) to f\/5.4 (810mm), stated for the Esprit 150ED specifically.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCorrected image circle:\u003c\/strong\u003e 36 mm fully illuminated, which the vendor states is compatible with both APS-C and full frame sensors. An APS-C sensor's roughly 28 mm diagonal sits inside the fully illuminated circle; a full-frame sensor spans 43.3 mm, so its extreme corners fall outside the 36 mm figure in the region Sky-Watcher covers with the full-frame compatibility statement. The published fields follow — 2.54 x 1.7 degrees full frame, 1.66 x 1.11 degrees APS-C.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eRequired backfocus:\u003c\/strong\u003e 90 mm as supplied, or 55 mm with the back focus spacer and M48 ring installed. 55 mm is the distance most cooled astronomical cameras and filter wheels are dimensioned to, so that is where most imaging trains settle.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eThread interface:\u003c\/strong\u003e M48, via the included M48 thread adapter that pairs with the 55 mm back focus configuration.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eFilter mounting:\u003c\/strong\u003e the built-in 2\" filter cell holds a 2-inch filter in the light path without adding a drawer or extra spacers to the train.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eRecommended Uses\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eWide-field deep-sky astrophotography:\u003c\/strong\u003e large emission and reflection nebulae, extended cluster fields and galaxy groups that run past the frame at 1050 mm.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNarrowband imaging:\u003c\/strong\u003e the faster f\/5.4 ratio offsets the transmission cost of narrow filters, and the built-in 2\" cell carries the filter in the light path.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLimited clear-sky sites:\u003c\/strong\u003e the published 68% exposure reduction against native f\/7 puts more finished signal into each usable night.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFull-frame and APS-C imaging:\u003c\/strong\u003e the 36 mm fully illuminated field is published as compatible with both, at 2.54 x 1.7 and 1.66 x 1.11 degrees respectively.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eCompatibility and Accessory Notes\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eSky-Watcher publishes this corrector for the Esprit 150ED, and the f\/7 (1050mm) to f\/5.4 (810mm) figures are stated for that telescope. Other Esprit models pair with their own correctors — including the separate Esprit 150EDX Flattener — and refractors from other makers have theirs. Send us the exact model printed on your tube and we will confirm which corrector belongs on it.\u003c\/p\u003e\n\u003cp\u003eThe box covers most of the spacing work: reducer, metal thread-on caps, back focus spacer and M48 thread adapter are all included. With the spacer and M48 adapter fitted, the corrector presents 55 mm of back focus, which is what a typical cooled camera plus filter wheel is built to consume. As supplied without them, it presents 90 mm, and that distance is filled by whatever sits between corrector and sensor.\u003c\/p\u003e\n\u003cp\u003eSend us your camera, filter wheel or drawer, off-axis guider and adapters and we will add the imaging train up with you and confirm which of the two configurations your setup wants. Filters thread into the built-in 2\" cell; cameras with an internal filter wheel simply leave that cell empty.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eGood to Know Before You Order\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eThe published figures are for the Esprit 150ED.\u003c\/strong\u003e 1050mm to 810mm and f\/7 to f\/5.4 are stated for that telescope. Other refractors reduce by their own numbers with their own correctors.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBackfocus sets corner star shape.\u003c\/strong\u003e The corrector presents 90 mm as supplied and 55 mm with the back focus spacer and M48 ring installed; the rest of the train is built to whichever figure you use.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e36 mm is the fully illuminated field.\u003c\/strong\u003e Sky-Watcher states compatibility with both APS-C and full frame sensors, with a full-frame sensor's outer corners lying beyond the 36 mm fully illuminated circle.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFilter cell takes 2-inch filters.\u003c\/strong\u003e The built-in cell is sized for 2\" filters; other filter sizes go elsewhere in the train.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eThis is the reducing corrector, not the flattener.\u003c\/strong\u003e The Esprit 150EDX Flattener is a separate part working at native focal length.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eVendor publishes no barcode for this SKU.\u003c\/strong\u003e The UPC we carry is 050234202152.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eVendor lists 2.0 lb for this item.\u003c\/strong\u003e That is the published weight; no separate optic-only mass appears in a specification table.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eFrequently Asked Questions\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eIs it difficult to set up?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe reducer threads into the imaging train once and stays there, and the parts that set the spacing — the back focus spacer and the M48 thread adapter — come in the box. The one decision is which backfocus you build to, 90 mm or 55 mm, and then adding camera, filter wheel and adapters up to that figure. Send us your components and we will do that arithmetic with you.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat focal length and focal ratio do I end up with?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eSky-Watcher publishes the Esprit 150ED as dropping from native f\/7 (1050mm) to f\/5.4 (810mm) with this reducer\/flattener fitted.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eHow much time does it save?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eSky-Watcher publishes a 68% reduction in exposure time compared with native f\/7.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWill it cover a full-frame sensor?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eSky-Watcher publishes a 36 mm fully illuminated field described as compatible with both APS-C and full frame sensors, quoting 2.54 x 1.7 degrees on a full-frame camera and 1.66 x 1.11 degrees on APS-C.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat comes in the box?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eSky-Watcher lists the reducer, metal thread-on caps, back focus spacer and M48 thread adapter.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCan I use filters with it?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eYes — a built-in 2\" filter cell mounts filters into the light path, so a 2-inch filter needs no separate drawer.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eSky-Watcher's own 0.77x corrector for the Esprit 150ED: f\/7 (1050mm) becomes f\/5.4 (810mm), exposure time drops by a published 68%, the frame opens to 2.54 x 1.7 degrees on full frame, and the back focus spacer, M48 adapter and thread-on caps are in the box. Tell us what camera and filters you run and we will confirm the 55 mm or 90 mm spacing with you before it ships.\u003c\/p\u003e","brand":"Sky-Watcher","offers":[{"title":"Default Title","offer_id":53896779858031,"sku":"S20215","price":730.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/S20215_Esprit150_RedFlat_web.jpg?v=1785253906"},{"product_id":"sky-watcher-esprit-70edx-evostar-100edx-field-flattener","title":"Sky-Watcher Esprit 70EDX \/ Evostar 100EDX Field Flattener","description":"\u003ch3\u003e\u003cstrong\u003eProduct Overview\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThis is Sky-Watcher's dedicated field corrector for two telescopes: the Esprit 70EDX and the Evostar 100EDX. A refractor objective brings light to focus on a gently curved surface; a camera sensor is flat. The flattener resolves that mismatch, so stars hold their shape out to the frame edges instead of drawing short radial streaks in the corners while the centre stays sharp.\u003c\/p\u003e\n\u003cp\u003eSky-Watcher publishes it as a 1.0X flattener with a 44 mm corrected image circle. The 1.0X figure means it corrects without reducing: focal length and focal ratio stay at the telescope's native values. The 44 mm circle encloses the 43.3 mm diagonal of a full-frame sensor and covers APS-C with margin to spare, so framing decisions come down to focal length rather than to how much of the sensor the corrector actually reaches.\u003c\/p\u003e\n\u003cp\u003eThe dual fitment is worth reading carefully, because Sky-Watcher's naming runs close together here. This part is published for the \u003cstrong\u003eEvostar\u003c\/strong\u003e 100EDX — the ED doublet. The \u003cstrong\u003eEsprit\u003c\/strong\u003e 100EDX, the super-apochromatic triplet, has its own corrector (S20217).\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eWho It's For\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThis is the corrector Sky-Watcher pairs with the Esprit 70EDX and the Evostar 100EDX, and it is the right part if you own either telescope and want flat, round stars across a large sensor at the scope's native focal length and ratio.\u003c\/p\u003e\n\u003cp\u003eOn the Esprit 70EDX — published by Sky-Watcher as 70 mm aperture, 455 mm focal length, f\/6.5 — that means very wide fields with corners that hold up: large emission nebulae, star fields, comets, mosaics. On the Evostar 100EDX doublet it means a longer-focal-length field with the same corner correction across a full-frame sensor.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eKey Features \u0026amp; Design\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eMatched to two telescopes:\u003c\/strong\u003e Sky-Watcher publishes compatibility with the Esprit 70EDX and the Evostar 100EDX. The correction is computed for those objectives rather than sold as a universal flattener.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e1.0X flattener:\u003c\/strong\u003e no reduction. The telescope's native focal length and focal ratio carry through the corrector unchanged.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e44 mm corrected image circle:\u003c\/strong\u003e the published figure covers a full-frame sensor's 43.3 mm diagonal and leaves APS-C well inside the corrected zone.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSingle-piece corrector:\u003c\/strong\u003e one optic in the imaging train between focuser and camera, with no separate elements to align.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOne part for a triplet and a doublet:\u003c\/strong\u003e Sky-Watcher publishes the same corrector against the 70 mm Esprit triplet and the 100 mm Evostar doublet, so a two-telescope setup built from those models needs one flattener rather than two.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eOptical \/ Mechanical Design\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eWhat it corrects:\u003c\/strong\u003e field curvature across the imaging field of the Esprit 70EDX and the Evostar 100EDX. The visible symptom it removes is corner stars that elongate radially, pointing away from the frame centre, while the middle of the frame focuses cleanly.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCorrected image circle:\u003c\/strong\u003e 44 mm, as published by Sky-Watcher. Sensor coverage follows directly from that number — a full-frame sensor measures 43.3 mm corner to corner and an APS-C sensor roughly 28 mm, so both sit inside the corrected field.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eMagnification factor:\u003c\/strong\u003e 1.0X. Sky-Watcher publishes no reduction, so the Esprit 70EDX continues to image at its published 455 mm and f\/6.5 with this part in the train, and the Evostar 100EDX at its own native figures.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eRequired backfocus and thread interface:\u003c\/strong\u003e Sky-Watcher does not publish a backfocus distance in millimetres or a thread size for this corrector on its product page, and no manual or datasheet is linked there. Those two numbers determine how the corrector spaces to your sensor, and corner star shape is what depends on getting the spacing right. Send us your camera, filter drawer or filter wheel and any adapters and we will lay the train out with you before you order.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eRecommended Uses\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eWide-field deep-sky astrophotography:\u003c\/strong\u003e on the Esprit 70EDX at 455 mm, large emission nebulae, open clusters, comets and star fields fill the frame with corners that stay clean.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLonger-focal-length imaging on the Evostar 100EDX:\u003c\/strong\u003e the same corner correction applied to the doublet's field.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLarge-sensor imaging:\u003c\/strong\u003e the 44 mm circle supports full-frame and APS-C cameras, including cooled astronomical CMOS bodies in those formats.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMosaic panels:\u003c\/strong\u003e flat corners let adjacent panels blend without a ring of distorted stars at every seam.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNarrowband and broadband alike:\u003c\/strong\u003e field curvature is a geometric error, so the correction applies regardless of the filter in front of the sensor.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eCompatibility and Accessory Notes\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eSky-Watcher lists two compatible telescopes for this corrector: the Esprit 70EDX and the Evostar 100EDX. The name similarity across their range is the thing to watch — the Esprit 100EDX triplet takes S20217, the Esprit 120EDX takes S20218 and the Esprit 150EDX takes S20219, each published against its own tube. Tell us the exact model printed on your telescope and we will confirm which corrector belongs on it.\u003c\/p\u003e\n\u003cp\u003eThe vendor does not publish the thread interface or the spacing distance to the sensor, so the adapters between this corrector and your camera cannot be specified from published data. Send us your camera model, filter wheel or drawer, and any off-axis guider in the train, and we will map the imaging train and tell you exactly what sits between the two.\u003c\/p\u003e\n\u003cp\u003eNothing about this part changes the mount side of the setup: it adds a short optic and roughly a pound behind the focuser rather than changing how the telescope mounts.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eGood to Know Before You Order\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eBackfocus is not published.\u003c\/strong\u003e Sky-Watcher gives no spacing figure in millimetres for this corrector. Corner star shape depends on hitting the correct sensor distance, and we can work that out with you from your specific camera and adapters.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eThread interface is not published.\u003c\/strong\u003e No thread size appears on the vendor page, so the camera-side connection is confirmed case by case rather than assumed.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEvostar 100EDX, not Esprit 100EDX.\u003c\/strong\u003e The 100 mm telescope named for this part is the Evostar doublet. The Esprit 100EDX triplet is served by S20217.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eThe 44 mm figure is published for these two telescopes.\u003c\/strong\u003e Other refractors pair with their own correctors, and the figure is not carried across to them.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIt is a flattener, not a reducer.\u003c\/strong\u003e Sky-Watcher publishes 1.0X, so focal length and focal ratio stay at each telescope's native values.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBox contents are not published.\u003c\/strong\u003e The vendor states no spacer, adapter or case as supplied with the corrector.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWeight figure is the vendor's shipping weight.\u003c\/strong\u003e Sky-Watcher lists 1.0 lb for this item and publishes no separate optic-only mass in a specification table.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eFrequently Asked Questions\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eIs it difficult to set up?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003ePhysically it is one optic that goes into the imaging train between the focuser and the camera, and it stays there. The part that takes attention is the spacing to the sensor, which Sky-Watcher does not publish for this corrector. Send us the camera and adapters you plan to use and we will lay out the train for you.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDoes it fit both telescopes, or do I need two?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eSky-Watcher publishes this one corrector against both the Esprit 70EDX and the Evostar 100EDX. If you own both, this is the single part for the pair.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDoes it change the focal length or focal ratio?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eNo. It is published as a 1.0X flattener, so the Esprit 70EDX images at its native 455 mm and f\/6.5 and the Evostar 100EDX at its own native figures.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWill it cover my full-frame camera?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe published corrected image circle is 44 mm and a full-frame sensor measures 43.3 mm across the diagonal, so the sensor sits inside the corrected field. APS-C sits well inside it.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eI have an Esprit 100EDX — is this the one?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe 100 mm telescope Sky-Watcher names here is the Evostar 100EDX doublet. For the Esprit 100EDX triplet the published corrector is S20217. Send us the model printed on your tube and we will match it.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat weight does it add to the imaging train?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eSky-Watcher lists 1.0 lb for this item. It is a small addition behind the focuser next to the camera, filters and any guider.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eA dedicated 1.0X flattener published for both the Esprit 70EDX and the Evostar 100EDX, with a 44 mm corrected circle — enough to keep stars round across a full-frame sensor at each telescope's native focal length. Sky-Watcher leaves the backfocus and thread figures unpublished, so we confirm the spacing with you against your own camera and adapters and send it out ready to drop into the train.\u003c\/p\u003e","brand":"Sky-Watcher","offers":[{"title":"Default Title","offer_id":53896786083951,"sku":"S20216","price":310.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/100_2_c036ec1b-e071-4037-9437-5adb55294a87.jpg?v=1785253987"}],"url":"https:\/\/ontariotelescope.com\/collections\/fr-sky-watcher.oembed","provider":"Ontario Telescope and Accessories","version":"1.0","type":"link"}