{"title":"Explore Scientific Flatteners \u0026 Reducers","description":"\u003cp\u003eExplore Scientific Flatteners \u0026amp; Reducers. Part of \u003ca href=\"\/collections\/flatteners-and-reducers\"\u003eFlatteners, Reducers \u0026amp; Correctors\u003c\/a\u003e.\u003c\/p\u003e","products":[{"product_id":"explores-scientific-2x-2-focal-extender","title":"Explore Scientific 2x 2-Inch Telecentric Focal Extender","description":"\u003ch3\u003e\u003cstrong\u003eProduct Overview\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThe Explore Scientific 2x Focal Extender is a 2-inch telecentric amplifier that doubles the effective focal length of the telescope it is fitted to. The body is 118mm long and 66mm wide, and Explore Scientific's current spec sheet gives its weight as 20 oz (0.57 kg). Explore Scientific describes it as compatible with both 1.25-inch and 2.0-inch eyepiece barrel sizes, for visual observing and for imaging.\u003c\/p\u003e\n\u003cp\u003eThe optics use multiple precision elements in a telecentric arrangement, with EMD coating on the air-to-glass surfaces and edge-blackened elements to hold contrast. Because the design is telecentric rather than a simple negative Barlow, the amplification factor stays at 2x regardless of how far the eyepiece or camera sits behind it.\u003c\/p\u003e\n\u003cp\u003ePractically, that means one focal extender doubles every eyepiece you own. A 20mm becomes a 10mm, a 14mm becomes a 7mm, and the apparent field and eye relief of each eyepiece carry through unchanged.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eWho It's For\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eObservers filling gaps in a set:\u003c\/strong\u003e two eyepieces plus this extender cover four magnifications, which is a compact way to build a range.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePlanetary and lunar observers:\u003c\/strong\u003e reaching high power by doubling a longer eyepiece keeps the eye relief of the longer eyepiece rather than the cramped eye position of a very short one.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEyeglass wearers:\u003c\/strong\u003e Explore Scientific specifically notes the telecentric design's benefit here, because eye relief is inherited from the eyepiece rather than compressed by the amplifier.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePlanetary imagers:\u003c\/strong\u003e doubling focal length raises image scale on the Moon and planets, and telecentricity keeps that factor predictable regardless of camera spacing.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eKey Features \u0026amp; Design\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e2x amplification, telecentric:\u003c\/strong\u003e the factor holds constant no matter what spacing the eyepiece or camera sits at, which a conventional Barlow does not do.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e2.0-inch barrel\u003c\/strong\u003e for 2-inch focusers and diagonals, with compatibility for both 1.25-inch and 2-inch eyepieces as published by Explore Scientific.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMultiple precision elements\u003c\/strong\u003e in the optical group; Explore Scientific does not publish the element count.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEMD coating on the air-to-glass surfaces,\u003c\/strong\u003e which is where a multi-element amplifier gains or loses transmission and contrast.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEdge-blackened elements\u003c\/strong\u003e to suppress the internal scatter that otherwise shows as a lowered contrast floor on planetary detail.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePublished dimensions:\u003c\/strong\u003e 118mm long, 66mm wide, 20 oz (0.57 kg).\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eOptical Design\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eA conventional Barlow lens is a negative group placed ahead of focus. It works, but its amplification factor depends on the distance between the lens and the eyepiece field stop — move the eyepiece further back and a nominal 2x becomes 2.3x or 2.5x. Anything that changes that distance, such as a diagonal inserted between the two or a different eyepiece with a deeper field stop, changes the effective magnification and makes the resulting figure an estimate.\u003c\/p\u003e\n\u003cp\u003eA telecentric design adds a positive group after the negative one, so the light leaving the assembly travels as a bundle of rays parallel to the optical axis. Two things follow. The amplification stays at exactly 2x whatever the spacing behind it, so the arithmetic on magnification and image scale remains exact. And the light entering the eyepiece arrives as though it came from a much slower telescope, which is easier on eyepiece designs that show edge aberrations at steep light cones.\u003c\/p\u003e\n\u003cp\u003eThe eyepiece keeps its own characteristics through the extender. Apparent field is unchanged, eye relief is unchanged, and the true field simply halves along with the doubling of magnification. That is why doubling a 14mm to reach 7mm is more comfortable than using a 7mm directly — the eye position belongs to the 14mm.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eRecommended Uses\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eHigh-power lunar and planetary observing without buying very short focal length eyepieces.\u003c\/li\u003e\n\u003cli\u003eSplitting double stars, where the extra magnification is what opens a tight pair.\u003c\/li\u003e\n\u003cli\u003ePlanetary imaging, where doubling focal length raises image scale on a small sensor.\u003c\/li\u003e\n\u003cli\u003eUse with fast telescopes, where the telecentric output is gentler on eyepiece edge performance.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eCompatibility and Accessory Notes\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eFits 2-inch focusers and diagonals.\u003c\/strong\u003e Explore Scientific publishes compatibility with both 1.25-inch and 2.0-inch eyepiece barrel sizes.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMagnification:\u003c\/strong\u003e double whatever the eyepiece gives on its own. In a 714mm telescope, a 20mm eyepiece goes from 36x to 71x; a 9mm goes from 79x to 159x.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEffective focal ratio:\u003c\/strong\u003e doubles as well. An f\/5 telescope behaves as f\/10 behind it, an f\/7 as f\/14 — which is the figure that matters for planetary imaging exposure.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eImaging:\u003c\/strong\u003e because the factor is spacing-independent, a camera can sit at whatever backfocus the train needs and the image scale stays predictable.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFocus travel:\u003c\/strong\u003e an extender shifts the focus point outward, so the focuser racks in further than it would without it. Most telescopes have the travel; a very short-travel focuser is worth a check, and we can look at that with you.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFilters:\u003c\/strong\u003e the 2-inch barrel accepts standard 2-inch threaded filters, so a lunar or minus-violet filter can sit ahead of the optics rather than at the eyepiece.\u003c\/li\u003e\n\u003c\/ul\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\u003eDoubling magnification also doubles the effect of atmospheric turbulence.\u003c\/strong\u003e On an unsteady night the extended view softens, which is seeing rather than the optics. On a steady night it is where the aperture shows what it can do.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIt needs a 2-inch focuser or diagonal.\u003c\/strong\u003e A telescope with only a 1.25-inch focuser is outside its range, and Explore Scientific makes a 1.25-inch focal extender for exactly that case — tell us your focuser and we will point you at the right one.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eExplore Scientific publishes two weight figures across revisions.\u003c\/strong\u003e The current spec sheet lists 20 oz (0.57 kg); an earlier sheet listed 752 grams (26.5 oz). Both are recorded as published rather than averaged into one number.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eThe element count is not published,\u003c\/strong\u003e so that row reads as not published below rather than carrying a guess. We can ask our Explore Scientific rep if it matters to you.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAn extender adds length to the imaging train.\u003c\/strong\u003e At 118mm it needs room behind the focuser, which is worth a look on a compact refractor with a short drawtube. Send us the telescope and we will check the geometry with you.\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\u003eNo — it slides into a 2-inch focuser or diagonal, and the eyepiece slides into it. Refocusing after fitting it is the only step, and there is nothing to align or adjust.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat is the difference between this and a Barlow?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eA Barlow's amplification varies with the spacing behind it, so a nominal 2x can drift to 2.5x depending on the eyepiece and whether a diagonal is in the path. This is telecentric, so 2x stays 2x at any spacing, and the exit light is parallel to the axis rather than converging.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWill it work with my 1.25-inch eyepieces?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eExplore Scientific publishes compatibility with both 1.25-inch and 2.0-inch eyepiece barrels. The unit itself seats in a 2-inch focuser or diagonal.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDoes it change my eye relief?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eNo. The eyepiece keeps its own eye relief and apparent field — only the magnification changes. That is why doubling a longer eyepiece is more comfortable than using a very short one.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCan I use it for photography?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eYes, particularly for the Moon and planets, where doubling focal length raises image scale. The telecentric design keeps the factor exact regardless of where the camera sensor sits.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eIn short: a telecentric 2x focal extender with a 2-inch barrel, EMD-coated and edge-blackened elements, 118mm long at 20 oz, that doubles every eyepiece in your case while leaving apparent field and eye relief untouched. If you would like to know exactly which magnifications it will open up with the eyepieces you already own, send us the list and your telescope's focal length and we will work them out.\u003c\/p\u003e","brand":"Explore Scientific","offers":[{"title":"Default Title","offer_id":44012806930543,"sku":"FE02-020","price":249.95,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/2xx_compact__37521.png?v=1766548235"},{"product_id":"explores-scientific-2x-1-25-field-extender","title":"Explore Scientific 2x 1.25-Inch Telecentric Focal Extender","description":"\u003ch3\u003e\u003cstrong\u003eProduct Overview\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThe Explore Scientific 2x Focal Extender is a 1.25-inch Barlow-type accessory that doubles the magnification of whatever eyepiece is placed in it. It is 96mm long, 45mm wide and weighs 260 grams (9.1 oz), and it is built on a telecentric optical layout using multiple precision lens elements rather than the single negative lens a simple Barlow uses.\u003c\/p\u003e\n\u003cp\u003eThe practical consequence of that layout is consistency. In a classic Barlow, the amplification factor depends on how far the eyepiece's field stop sits from the negative lens, so a 2x Barlow becomes a 2.3x or a 2.7x when spacing changes — when a diagonal goes in between, for instance, or when a different eyepiece design puts its field stop somewhere else. A telecentric design produces an exit beam whose rays run parallel to the optical axis, which holds the magnification factor at 2x regardless of spacing and keeps the eyepiece's own eye relief and image quality intact.\u003c\/p\u003e\n\u003cp\u003eThe result is that one 2x extender effectively doubles the number of magnifications your eyepiece set delivers: a 20mm becomes a 10mm-equivalent power, a 15mm becomes 7.5mm, a 30mm becomes 15mm — each while keeping the eye relief characteristics of the longer eyepiece.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eWho It's For\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eEyeglass wearers:\u003c\/strong\u003e this is the most useful case of all. Short-focal-length eyepieces are where eye relief runs out; using a longer eyepiece behind a telecentric extender gives high magnification while retaining the comfortable eye position of the longer eyepiece.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLunar and planetary observers\u003c\/strong\u003e who need to reach the magnifications where surface detail lives on the nights when seeing allows it.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePlanetary imagers:\u003c\/strong\u003e doubling the focal length increases the image scale at the sensor, which is how a small planetary disc is made to cover enough pixels to resolve detail.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eKey Features \u0026amp; Design\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eTelecentric optical layout:\u003c\/strong\u003e the defining feature. Multiple precision lens elements produce a parallel exit beam, holding the 2x factor constant regardless of the distance to the eyepiece.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eConsistent 2x amplification:\u003c\/strong\u003e the number on the barrel is the number you get, in a diagonal or straight into the focuser.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePreserves eye relief:\u003c\/strong\u003e the eyepiece behaves as it normally would, so its comfortable eye position carries through to the higher magnification.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e1.25-inch barrel:\u003c\/strong\u003e fits any standard 1.25-inch focuser or diagonal, and accepts any 1.25-inch eyepiece.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePublished dimensions:\u003c\/strong\u003e 96mm long, 45mm wide, 260 grams (9.1 oz).\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eOptical Design\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eA Barlow lens is a diverging optical group placed ahead of focus. It makes the converging light cone from the telescope shallower, which pushes the focal point further back and increases the effective focal length — and therefore the magnification. In its simplest form a single negative lens does the job, and it does it well enough for most purposes.\u003c\/p\u003e\n\u003cp\u003eThe weakness of the simple form is that the amount of amplification depends on where the eyepiece's field stop lands relative to that negative lens. Move the eyepiece further back and the factor rises. Insert a star diagonal between the Barlow and the eyepiece and the factor rises again. That is why a nominal 2x Barlow can end up delivering anywhere from 2x to nearly 3x depending on how it is used, which makes it hard to know what magnification you are actually observing at.\u003c\/p\u003e\n\u003cp\u003eA telecentric design solves this with a multi-element group that does more than diverge the beam. It re-forms the light so the chief rays exit parallel to the optical axis, which means the eyepiece behind it sees essentially the same geometry no matter where it sits. The amplification factor stays at 2x, the eyepiece's designed eye relief is preserved rather than compressed or stretched, and the correction the eyepiece was designed to deliver is not disturbed by the extra optics ahead of it.\u003c\/p\u003e\n\u003cp\u003eThere is one physical consequence worth understanding. Doubling the effective focal length also doubles the effective focal ratio: an f\/6 telescope behaves like an f\/12 one behind this extender. That halves the exit pupil for any given eyepiece and reduces image brightness accordingly, which is why focal extenders belong to lunar, planetary and double-star observing rather than to faint deep-sky work.\u003c\/p\u003e\n\u003cp\u003eExplore Scientific does not publish the exact element count for this extender, describing it as multiple precision lens elements, and does not publish a filter thread specification. Those rows are marked unpublished below rather than estimated.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eRecommended Uses\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eHigh-power lunar observing, where doubling a mid-range eyepiece reaches crater-floor detail along the terminator.\u003c\/li\u003e\n\u003cli\u003ePlanetary observing on steady nights — Jovian belt structure, the Cassini division, Martian surface markings.\u003c\/li\u003e\n\u003cli\u003ePlanetary and lunar imaging, where doubling the focal length gives the image scale a small planetary disc needs.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eCompatibility and Accessory Notes\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eFits any 1.25-inch focuser or diagonal,\u003c\/strong\u003e and accepts any 1.25-inch eyepiece. In a 2-inch focuser it seats in a 2-inch to 1.25-inch adapter.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMagnification:\u003c\/strong\u003e telescope focal length × 2 ÷ eyepiece focal length. In a 952mm telescope, a 20mm eyepiece goes from 48x to 95x; a 12mm from 79x to 159x.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEffective focal ratio:\u003c\/strong\u003e doubles. An f\/6 telescope works at f\/12 behind the extender, and an f\/10 at f\/20.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eExit pupil:\u003c\/strong\u003e halves for a given eyepiece, which is why the extender pairs best with mid and long focal length eyepieces rather than the shortest one in the case.\u003c\/li\u003e\n\u003c\/ul\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\u003eDoubling magnification halves image brightness for a given eyepiece.\u003c\/strong\u003e That is fine on the Moon and the planets, and it is why deep-sky observing generally stays at native focal length. The extender is a Solar System and double-star tool.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSeeing sets the ceiling, not the optics.\u003c\/strong\u003e On a turbulent night, higher magnification enlarges the turbulence along with the target. The extender earns its keep on steady nights, which is exactly what it was made for.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePairing it with your shortest eyepiece often overshoots.\u003c\/strong\u003e A 2x extender behind a 5mm in a metre-focal-length telescope produces magnification most apertures cannot support. Mid-range eyepieces are the productive partners, and the results are visibly better.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eExplore Scientific does not publish the element count or a filter thread figure\u003c\/strong\u003e for this extender, so those rows read as unpublished rather than estimated. If either matters, ask and we will check with our Explore Scientific rep.\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\u003eNo — the extender goes into the focuser or diagonal and the eyepiece goes into the extender. There is nothing to adjust, and because the design is telecentric, the spacing does not need to be set precisely to get the stated 2x.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat is the difference between this and a regular Barlow?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eA simple Barlow's amplification factor changes with spacing, so a nominal 2x can become 2.5x or more once a diagonal or a different eyepiece is involved. A telecentric design produces a parallel exit beam, so it stays at 2x regardless, and it preserves the eyepiece's own eye relief instead of altering it.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat magnification will I get?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eDouble whatever the eyepiece gives on its own. Telescope focal length × 2, divided by eyepiece focal length. A 1000mm telescope with a 20mm eyepiece goes from 50x to 100x.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eIs it good for eyeglass wearers?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eIt is one of the best answers there is. Instead of buying a very short eyepiece with minimal eye relief, you use a longer, more comfortable eyepiece behind the extender and get the same magnification with the eye relief the longer eyepiece was designed around.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eIn short: a 1.25-inch 2x focal extender with a telecentric multi-element design that holds its amplification factor and its eye relief regardless of spacing, at 96mm long and 260 grams. It doubles the number of magnifications your eyepiece set delivers and is particularly useful if you observe with glasses on. If you would like a second opinion on which of your eyepieces it pairs with best, send us the list and your telescope's focal length and we will work it through with you.\u003c\/p\u003e","brand":"Explore Scientific","offers":[{"title":"Default Title","offer_id":44012807716975,"sku":"FE02-125","price":165.95,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/2x_compact__89719.png?v=1766548241"},{"product_id":"explore-scientific-3x-1-25-field-extender","title":"Explore Scientific 3x 1.25-Inch Telecentric Focal Extender","description":"\u003ch3\u003e\u003cstrong\u003eProduct Overview\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThe Explore Scientific 3x Focal Extender is a 1.25-inch telecentric amplifier that triples the magnification of whatever eyepiece is placed in it. Explore Scientific publishes a length of 93mm, a width of 45mm and a weight of 249 grams (8.7 oz), and describes the optical design as telecentric, using multiple precision lens elements to deliver light rays parallel to the optical axis.\u003c\/p\u003e\n\u003cp\u003eThat last point is what separates a telecentric focal extender from a conventional Barlow. In a Barlow, the amplification factor depends on how far the eyepiece field stop sits from the negative lens — add an extension or a diagonal into the train and the stated 2x quietly becomes 2.4x. A telecentric design sends the light out parallel, so the magnification stays at 3x regardless of the spacing behind it. What you calculate is what you get.\u003c\/p\u003e\n\u003cp\u003eThe other consequence is eye relief. A 3x extender lets a comfortable long-focal-length eyepiece do the work of a very short one: a 15mm eyepiece behind this unit performs like a 5mm while keeping the 15mm's eye relief. For eyeglass wearers and for anyone who finds short-focal-length eyepieces cramped, that is the main reason to own one.\u003c\/p\u003e\n\u003ch3\u003e\u003cstrong\u003eWho It's For\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eLunar and planetary observers\u003c\/strong\u003e who want to reach high magnification without buying the very shortest eyepieces in a series.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEyeglass wearers:\u003c\/strong\u003e the extender preserves the eye relief of the eyepiece in front of it, which is exactly what short eyepieces sacrifice.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOwners of fast telescopes:\u003c\/strong\u003e at f\/4 or f\/5 a 3x extender turns the effective focal ratio into f\/12 or f\/15 at the eyepiece, which eases the demands on eyepiece design at the field edge.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDouble-star observers\u003c\/strong\u003e who need magnification on demand without swapping through a whole case.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePlanetary imagers\u003c\/strong\u003e using a 1.25-inch camera nose, where telecentric output keeps the amplification factor predictable in the image scale calculation.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003e\u003cstrong\u003eKey Features \u0026amp; Design\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e3x magnification factor:\u003c\/strong\u003e a full three times, applied to whatever eyepiece is inserted.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTelecentric optical design:\u003c\/strong\u003e multiple precision lens elements arranged to emit rays parallel to the optical axis, so the amplification does not drift with spacing.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEye relief preserved:\u003c\/strong\u003e the eyepiece keeps its own eye relief, so a long eyepiece at high power stays comfortable.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e1.25-inch barrel:\u003c\/strong\u003e fits any standard 1.25-inch focuser or diagonal.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePublished dimensions:\u003c\/strong\u003e 93mm long, 45mm wide, 249 grams (8.7 oz).\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eConsistent scale for imaging:\u003c\/strong\u003e because the factor is fixed, image scale calculations for planetary capture stay reliable.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003e\u003cstrong\u003eOptical Design\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eA conventional Barlow lens is a negative element placed ahead of focus. It makes the converging light cone from the telescope shallower, which pushes focus further back and increases the effective focal length. The catch is that the amount of increase depends on the distance between the negative lens and the eyepiece field stop. Move the eyepiece back — by adding an extension tube, a filter wheel, or a diagonal in the wrong place — and the amplification climbs above the printed figure.\u003c\/p\u003e\n\u003cp\u003eA telecentric design solves this by adding positive elements behind the negative group so that the exit rays leave parallel to the optical axis rather than diverging. Parallel rays mean the effective amplification stops depending on how far away the next component sits. A 3x telecentric extender is 3x with a diagonal in the train, 3x with an extension tube, and 3x with a camera on the back.\u003c\/p\u003e\n\u003cp\u003eThe trade with any amplifier is light. Tripling magnification spreads the same photons over nine times the area, so the image is dimmer and the exit pupil shrinks to a third of what the eyepiece alone would give. That is why an extender belongs on bright targets: the Moon, the planets, double stars, and the brighter compact deep-sky objects.\u003c\/p\u003e\n\u003ch3\u003e\u003cstrong\u003eRecommended Uses\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eHigh-power lunar and planetary observing without a dedicated short-focal-length eyepiece.\u003c\/li\u003e\n\u003cli\u003eSplitting close double stars.\u003c\/li\u003e\n\u003cli\u003ePlanetary and lunar imaging with a 1.25-inch camera, where a predictable amplification factor matters to image scale.\u003c\/li\u003e\n\u003cli\u003eExtending a modest eyepiece set into a larger range of magnifications.\u003c\/li\u003e\n\u003cli\u003eObserving with eyeglasses at high power, where a long eyepiece behind the extender keeps the eye relief.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003e\u003cstrong\u003eCompatibility and Accessory Notes\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eFits any 1.25-inch focuser or diagonal.\u003c\/strong\u003e In a 2-inch focuser it takes a 2-inch to 1.25-inch adapter.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eResulting magnification:\u003c\/strong\u003e telescope focal length ÷ eyepiece focal length × 3. A 20mm eyepiece in a 952mm telescope gives 143x; a 15mm in a 1200mm gives 240x.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEffective focal length:\u003c\/strong\u003e the telescope behaves as though its focal length were tripled — a 714mm f\/7 refractor becomes 2142mm at f\/21 at the eyepiece.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePairing:\u003c\/strong\u003e mid and long focal length eyepieces are the natural partners. A 25mm, 20mm or 15mm behind this unit produces the equivalent of an 8.3mm, 6.7mm or 5mm.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWhere it stops helping:\u003c\/strong\u003e putting a 3mm or 4mm eyepiece behind a 3x extender exceeds the useful magnification of nearly any aperture. The long end of your case is where the gains are.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eImaging:\u003c\/strong\u003e a 1.25-inch camera nose fits directly. Because the design is telecentric, the amplification stays at 3x whatever the backfocus, which keeps the plate scale calculation honest.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFilters:\u003c\/strong\u003e Explore Scientific does not publish the filter thread specification for this extender, so we are not quoting one. Filters can also be threaded onto the eyepiece instead, which is the usual arrangement.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003e\u003cstrong\u003eGood to Know Before You Order\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e3x is a large step, and the atmosphere has a vote.\u003c\/strong\u003e On a steady night in a well-cooled telescope it opens up the top of the magnification range; on a turbulent night a 2x extender or the eyepiece alone will show more detail. Many observers keep both factors on hand for that reason, and we stock the 2x as well.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eThe image gets dimmer as it gets bigger.\u003c\/strong\u003e Three times the magnification means roughly one ninth the surface brightness, which is why bright targets are where an extender earns its place.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eExplore Scientific publishes two slightly different sets of physical figures for this item\u003c\/strong\u003e — 93mm and 249 grams on the current product page, 96mm and 260 grams on the spec sheet supplied with earlier stock. The optical specification is the same; the difference is in production revisions. If the exact dimension matters for a case, ask us and we will confirm it with our rep.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eElement count and coatings are not published\u003c\/strong\u003e beyond the description of multiple precision lens elements, so those rows read \"Not published by vendor\" below rather than carrying an estimate.\u003c\/li\u003e\n\u003c\/ul\u003e\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\u003eNo — the extender goes into the focuser or diagonal, the eyepiece goes into the extender, and that is the whole procedure. Refocusing after fitting it is normal, since the extender moves the focal point outward.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat is the difference between this and a Barlow?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eA Barlow's amplification changes with the spacing behind it. A telecentric extender sends light out parallel to the optical axis, so 3x stays 3x whatever else is in the train — diagonal, extension tube or camera.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDoes it reduce eye relief?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eNo, and that is one of the main reasons to use one. The eyepiece keeps its own eye relief, so a 20mm eyepiece at 3x gives the magnification of a 6.7mm with the comfort of a 20mm.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhich eyepieces should I pair it with?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe mid and long focal lengths in your case. A 25mm, 20mm or 15mm become the equivalent of 8.3mm, 6.7mm and 5mm. Very short eyepieces behind a 3x go past what most apertures can use.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCan I use it for photography?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eYes, for lunar and planetary imaging with a 1.25-inch camera. The fixed telecentric factor is a practical advantage, because the image scale calculation stays correct no matter what spacing the camera ends up at.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWill it work with my telescope?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eAny telescope with a 1.25-inch focuser or diagonal takes it, and a 2-inch focuser takes it through an adapter. Whether 3x is the right factor depends on your focal length and aperture — send us those and we will tell you which factor suits.\u003c\/p\u003e\n\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eIn short: a 1.25-inch telecentric 3x focal extender at 93mm and 249 grams that triples magnification with a fixed, spacing-independent factor and leaves the eyepiece's eye relief intact — a straightforward way to turn the comfortable half of your eyepiece case into a high-power set. If you would like a recommendation on whether 2x or 3x suits your telescope's focal length better, send us the figures and we will work it out with you.\u003c\/p\u003e","brand":"Explore Scientific","offers":[{"title":"Default Title","offer_id":44012809027695,"sku":"FE03-125","price":193.95,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/3x_compact__06275.png?v=1766548248"},{"product_id":"3-field-flattener-7x-focal-reducer","title":"3\" FIELD FLATTENER .7X FOCAL REDUCER","description":"\u003cp\u003eExplore Scientific’s 3-inch Field Flattener\/0.7x Focal Reducer is a multi-faceted accessory designed to enhance your astrophotography experiences. As a field flattener, this piece addresses the edge-of-field aberrations caused by curved focal planes to ensure your night at the eyepiece will result in crisp, true images.\u003c\/p\u003e\n\u003cp\u003eAs a focal reducer, this device will reduce your f-ratio by 0.7, which results in a wider field of view, brighter images and less exposure time. Recommended for our 127mm and 152mm refracting telescopes (excluding our doublet refractors), this field flattener\/focal reducer boasts fully multi-coated optics.\u003cbr\u003e\u003cbr\u003eThis item comes with a threaded adapter that threads onto the Explore Scientific 2-inch rack-and-pinion focuser. Threaded attachment to a 2.5-hex focuser, which comes stock on our 127mm APO telescopes, requires purchase of an additional adapter. \u003c\/p\u003e\n\u003cp\u003eThe field flattener\/focal reducer offers 55 mm of back focus from the rear face of the device. The M42x0.75 adapter adds 3 mm, so the sensor needs to be 52 mm from the face of the adapter.\u003cbr\u003e\u003cbr\u003eTo connect to the 2.5 hex focuser, purchase item number\u003cspan\u003e \u003c\/span\u003e\u003ca href=\"https:\/\/ontariotelescope.com\/products\/explore-scientific-adapter-for-fffr507x-00-to-2-5-hex-focuser\" target=\"_blank\" title=\"FFFR adapter\" rel=\"noopener\"\u003e510366\u003c\/a\u003e.\u003c\/p\u003e\n\u003cp\u003eWhile technically this was designed for the f\/8 system, through user experiences and our subsequent testing we have concluded that our 3-inch field flattener\/reducer performs very well with our f\/7.5 refractors.\u003c\/p\u003e\n\u003ch2 style=\"margin: 0px 0px 2em; font-family: Arial, Helvetica, sans-serif; font-weight: normal; line-height: 20px; color: rgb(34, 34, 34); text-rendering: optimizeLegibility; font-size: 14px; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(236, 229, 227); text-transform: uppercase; background-color: rgb(255, 255, 255);\"\u003e\n\u003cbr\u003e\u003cbr\u003e\n\u003c\/h2\u003e","brand":"Explore Scientific","offers":[{"title":"Default Title","offer_id":44013211680879,"sku":"FFFR507X-00","price":553.95,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/f1_1024x1024__16033.jpg?v=1766548832"},{"product_id":"explore-scientific-hr-variable-coma-corrector-with-adapters","title":"Explore Scientific HR Variable Coma Corrector 2-inch WITH M42 and M48 Camera Adapters","description":"\u003ch2\u003eProduct Overview\u003c\/h2\u003e\u003cp\u003eThe Explore Scientific HR Variable Coma Corrector is a 2-inch corrector for Newtonian reflectors, designed by the optical designer Harrie Rutten and EMC coated to hold down internal reflections. This is item HRCC02-00, the version supplied \u003cstrong\u003ewith\u003c\/strong\u003e camera adapters: both an M42x0.75 and an M48x0.75 adapter are in the box, along with three thumbscrews and a protective cap. Explore Scientific publishes a weight of 1 lb (0.45 kg), a diameter of 69.3 mm and a height of 147.2 mm.\u003c\/p\u003e\u003cp\u003eExplore Scientific offers the same corrector without those adapters as item HRCC02-01, at a lower price. If you intend to screw a camera directly onto the corrector, this is the version to buy.\u003c\/p\u003e\u003ch2\u003eWho It's For\u003c\/h2\u003e\u003cp\u003eAnyone imaging or observing with a fast parabolic Newtonian who is tired of comet-shaped stars in the corners. Coma is inherent to the paraboloid: it grows with distance from the optical axis and it grows fast as the focal ratio drops, so an f\/4 mirror shows it well inside the field of a 2-inch eyepiece while an f\/8 mirror mostly hides it. This corrector is the standard remedy, and Explore Scientific specifies it down to around f\/3.9.\u003c\/p\u003e\u003cp\u003eChoose this HRCC02-00 version if you are attaching a camera. The two threaded adapters are what let a DSLR or dedicated astro camera screw straight onto the corrector at a fixed, repeatable spacing, which is exactly what you want when you are trying to reproduce a working imaging train night after night.\u003c\/p\u003e\u003ch2\u003eKey Features \u0026amp; Design\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003e2-inch coma corrector for parabolic Newtonian reflectors, specified for fast mirrors from around f\/3.9\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIncludes both M42x0.75 and M48x0.75 camera adapters\u003c\/strong\u003e for a direct screw-on camera connection\u003c\/li\u003e\n\u003cli\u003eOptical design by Harrie Rutten\u003c\/li\u003e\n\u003cli\u003eEMC coating to suppress internal reflections and ghosting on bright stars\u003c\/li\u003e\n\u003cli\u003eVariable spacer with markings, so the corrector can be set for different telescopes\u003c\/li\u003e\n\u003cli\u003eThree thumbscrews and a protective cap supplied\u003c\/li\u003e\n\u003cli\u003e1 lb (0.45 kg), 69.3 mm diameter, 147.2 mm tall\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch2\u003eOptical Design\u003c\/h2\u003e\u003cp\u003eA parabolic mirror brings light to a sharp focus on axis and nowhere else. Off axis, rays striking different zones of the mirror land at slightly different places, and the resulting flare is coma: stars grow a one-sided tail that points away from field centre and lengthens the further out you look. Because the effect scales roughly as the inverse square of the focal ratio, halving the f-number quadruples the coma — which is why a fast Newtonian, the very telescope you want for wide-field imaging, is also the one that shows the aberration worst.\u003c\/p\u003e\u003cp\u003eThe corrector sits in the converging beam ahead of focus and applies an equal and opposite aberration, straightening those tails back into points. Its distance from the sensor or eyepiece field stop is what determines how completely it does that, and it is why the spacer is marked rather than fixed — different telescopes want different spacings, and the markings let you find yours and return to it. The EMC coating matters more here than on a simple accessory, because a multi-element group sitting in a converging beam is a good place to generate ghost images from bright stars if the surfaces are not properly treated.\u003c\/p\u003e\u003ch2\u003eRecommended Uses\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003eDeep-sky imaging with a fast parabolic Newtonian, where corner stars would otherwise flare\u003c\/li\u003e\n\u003cli\u003eWide-field visual observing at low power in a fast Dobsonian, sharpening the field edge\u003c\/li\u003e\n\u003cli\u003eAny Newtonian imaging train where the camera needs to screw on at a fixed, repeatable spacing\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch2\u003eCompatibility and Accessory Notes\u003c\/h2\u003e\u003cp\u003eThis corrects coma; it is not a focal reducer and it will not shorten your focal length or speed up your system. It is designed for parabolic primary mirrors — Newtonians and Dobsonians — and is not intended for refractors, which need a field flattener instead. It fits a 2-inch focuser and needs enough in-travel to reach focus with the corrector and camera in place, which on some Newtonians means a low-profile focuser or a shortened tube. The M42x0.75 and M48x0.75 adapters supplied here cover both common camera thread standards, so you will still need a T-ring for your specific camera body but not a separate thread adapter. Tell us your telescope and camera and we will confirm the spacing and back-focus before you order.\u003c\/p\u003e\u003ch2\u003eGood to Know Before You Order\u003c\/h2\u003e\u003cp\u003eThe one decision to get right is which version you want. This HRCC02-00 comes with the M42 and M48 adapters. The cheaper HRCC02-01 is the identical corrector \u003cem\u003ewithout\u003c\/em\u003e them, and if you buy that one and later want a screw-on camera connection you will be sourcing adapters separately — which usually costs more than the difference between the two listings. Buy this one if a camera is anywhere in your plans. Note also that reaching focus with a corrector in the train is the commonest snag on Newtonians; if you have not used one on your telescope before, check your focuser travel or ask us.\u003c\/p\u003e\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\u003cp\u003e\u003cstrong\u003eWhat is the difference between HRCC02-00 and HRCC02-01?\u003c\/strong\u003e The adapters. This version (HRCC02-00) includes M42x0.75 and M48x0.75 camera adapters. HRCC02-01 is the same corrector supplied without them, at a lower price.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWill it work on my f\/5 Dobsonian?\u003c\/strong\u003e Yes — it is designed for parabolic Newtonians and Explore Scientific specifies it for fast mirrors from around f\/3.9, so f\/5 is well within range. Reaching focus is the thing to check, not the optics.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eDoes it change my focal length?\u003c\/strong\u003e No. It corrects coma and leaves the focal ratio alone. If you want a shorter focal length you are after a focal reducer, which is a different product.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eCan I use it visually?\u003c\/strong\u003e Yes. It sharpens stars at the edge of the field with wide-angle eyepieces at low power, though the gain is most obvious on fast mirrors.\u003c\/p\u003e\u003ch2\u003eBottom Line\u003c\/h2\u003e\u003cp\u003eThe Harrie Rutten HR coma corrector in its complete form — EMC coated, marked variable spacer, and both M42 and M48 camera adapters in the box. If you are imaging with a fast Newtonian, this is the version that saves you a second purchase. Send our Bolton team your telescope and camera and we will check the spacing with you.\u003c\/p\u003e","brand":"Explore Scientific","offers":[{"title":"Default Title","offer_id":44013213417583,"sku":"HRCC02-00","price":290.95,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/explore-scientific-es-hr-coma-corrector-telescope-house-0510330_2__40349.png?v=1766548839"},{"product_id":"explore-scientific-adapter-for-fffr507x-00-to-2-5-hex-focuser","title":"Explore Scientific Adapter for FFFR507X-00 0.7x Corrector to 2.5-Inch Hex Focuser","description":"\u003ch3\u003e\u003cstrong\u003eProduct Overview\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThis is the Explore Scientific mechanical adapter that joins the FFFR507X-00 3-inch 0.7x field flattener and focal reducer to a 2.5-inch hex focuser. It carries no optical elements of its own. Its entire job is to hold two components of different diameters concentric, square to the optical axis, and at whatever spacing the corrector was designed for — which, in an imaging train, is the difference between round stars in the corners and elongated ones.\u003c\/p\u003e\n\u003cp\u003eThe FFFR507X-00 is a 3-inch corrector, sized for the larger focusers fitted to Explore Scientific's bigger refractors. A 2.5-inch hex focuser has a smaller drawtube, so on its own the corrector has nothing to seat against. The adapter is the interface that makes that pairing mechanically possible.\u003c\/p\u003e\n\u003cp\u003eExplore Scientific does not publish a specification table for this item — no dimensions, no thread callouts, no weight and no optical path length. Everything below that is not in their data is stated as unpublished rather than estimated, and we are glad to take a specific question to our Explore Scientific contact on your behalf.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eWho It's For\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eOwners of the FFFR507X-00 3″ 0.7x corrector\u003c\/strong\u003e who want to use it on a telescope fitted with a 2.5-inch hex focuser rather than a 3-inch one.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eImagers assembling a fixed, repeatable optical train,\u003c\/strong\u003e where a purpose-made adapter is more rigid and more concentric than a stack of general-purpose rings.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAnyone who has changed focusers or telescopes\u003c\/strong\u003e and needs to carry an existing corrector across to the new setup.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eObservers troubleshooting corner star shapes,\u003c\/strong\u003e where a mechanical mismatch in the train is one of the usual causes.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eKey Features \u0026amp; Design\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003ePurpose-built interface:\u003c\/strong\u003e made specifically for the FFFR507X-00 to 2.5-inch hex focuser pairing rather than adapted from a generic ring.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMechanical only:\u003c\/strong\u003e no lenses and no coatings, so it introduces no aberrations of its own and needs no cleaning regime beyond keeping the mating faces clean.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eConcentricity and squareness:\u003c\/strong\u003e the two functions that matter in an adapter. A part machined for a specific pair holds the corrector on-axis more reliably than a chain of step rings does.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFixed geometry:\u003c\/strong\u003e a single machined part contributes one known length to the train rather than the accumulated tolerance of several stacked components.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePart of the Explore Scientific accessory line,\u003c\/strong\u003e so the mating dimensions are drawn from the same drawings as the focuser and the corrector it joins.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eRecommended Uses\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eFitting the FFFR507X-00 3-inch 0.7x reducer and flattener onto a 2.5-inch hex focuser.\u003c\/li\u003e\n\u003cli\u003eBuilding a deep-sky imaging train that reduces focal length and flattens the field in one component.\u003c\/li\u003e\n\u003cli\u003eMoving an existing corrector between telescopes with different focuser sizes.\u003c\/li\u003e\n\u003cli\u003eReplacing an improvised stack of step rings with a single machined interface.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eCompatibility and Accessory Notes\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eCorrector side:\u003c\/strong\u003e made for the Explore Scientific FFFR507X-00, the 3-inch 0.7x field flattener and focal reducer.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFocuser side:\u003c\/strong\u003e made for the 2.5-inch hex focuser.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSpacing matters downstream of it.\u003c\/strong\u003e A reducer and flattener has a designed distance from its rear surface to the sensor, and that distance is set by the parts that follow the adapter — the camera, the filter wheel, any spacer rings. If you send us the camera and any filter wheel or off-axis guider you plan to use, we will work through the spacing with you.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFilters in the train add optical path.\u003c\/strong\u003e Glass in the light path shifts focus slightly, which is one of the more common reasons a train that measures correctly still does not quite deliver. It is straightforward to allow for once it is accounted for.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eExplore Scientific publishes no thread specification, length or weight\u003c\/strong\u003e for this adapter, so those rows read as unpublished below. For a specific figure, ask us and we will take it to our Explore Scientific contact before you commit to an order.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOther correctors:\u003c\/strong\u003e this part is specified for the FFFR507X-00. If you have a different flattener or reducer in mind, send us the model and we will look at whether the interface suits it.\u003c\/li\u003e\n\u003c\/ul\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\u003eIt is a mechanical adapter, not a corrector.\u003c\/strong\u003e The optical work is done by the FFFR507X-00; this part positions it. Both are needed for the pairing, and we can supply them together.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eExplore Scientific publishes no specification table for it.\u003c\/strong\u003e No dimensions, thread callouts, optical path length or weight appear on their product page, so the table below records those rows as unpublished rather than estimated. If a figure decides the purchase for you, ask and we will get it from our Explore Scientific contact first.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBack-focus is the specification that governs the result.\u003c\/strong\u003e The adapter contributes a fixed length; the remainder of the distance to the sensor comes from spacers and from the camera itself. Sending us the full list of what sits behind the corrector is the quickest way to get that right the first time.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIt is a narrow-purpose part.\u003c\/strong\u003e It exists for one corrector and one focuser size, which is precisely why it fits well. For any other combination, we would rather check the fit with you than have the wrong part arrive.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNothing else is required to use it\u003c\/strong\u003e beyond the corrector and the focuser it was made for — there is no separate clamp, ring or tool involved.\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\u003eNo — it is a single machined part that goes between the corrector and the focuser and then stays there. There is nothing to align, collimate or calibrate on the adapter itself. The one job that repays a few minutes is measuring the spacing from the back of the corrector to your camera sensor, and we will happily work that out with you.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDoes it contain any glass?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eNo. It is purely mechanical, so it adds no aberrations, no reflections and no light loss of its own.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat does the FFFR507X-00 do?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eIt is a 3-inch field flattener and 0.7x focal reducer. It flattens the curved focal plane that a refractor naturally produces, so stars stay round toward the corners of a sensor, and it shortens the effective focal length to 0.7 of its native value — a wider field and a faster focal ratio at the same time.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWill it change my back-focus?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eAny component in the train contributes length, and this one is no exception. Explore Scientific does not publish its optical path length, so we are not going to quote a figure. Send us the parts list for your train and we will work the spacing through with you.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDoes it fit other Explore Scientific focusers?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eIt is specified for the 2.5-inch hex focuser. If your telescope has a different focuser, send us the model and we will check the interface for you before you order.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eIs a camera adapter included?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eNo. This part joins the corrector to the focuser; the connection from the corrector to your camera is a separate item, chosen to suit the camera and the spacing your train needs.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCan I use it for visual observing?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe FFFR507X-00 it supports is an imaging corrector, so the pairing is aimed at cameras. It is mechanically harmless in a visual train, though there is little for it to do there.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eIn short: a mechanical adapter that lets the Explore Scientific FFFR507X-00 3-inch 0.7x flattener and reducer sit on a 2.5-inch hex focuser, with no optics of its own and one job to do properly. Explore Scientific publishes no dimensions for it, so if you would like exact figures before you order, or help laying out the spacing between the corrector and your camera, send us the list of what is in your imaging train and we will map it out with you.\u003c\/p\u003e","brand":"Explore Scientific","offers":[{"title":"Default Title","offer_id":44013400981615,"sku":"510366","price":138.95,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/ES_0510366_2_3000x__04467.jpg?v=1766553257"},{"product_id":"explore-scientific-2-3x-focal-extender","title":"Explore Scientific 3x 2-Inch Telecentric Focal Extender","description":"\u003ch3\u003e\u003cstrong\u003eProduct Overview\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThe Explore Scientific FE03-020 is a 3x focal extender in the 2-inch format, 125mm long and 66mm wide. Explore Scientific list its weight two ways — 22 oz on the specification table and 1.7 lbs. on the product page — and both figures are reproduced verbatim below rather than reconciled by us.\u003c\/p\u003e\n\u003cp\u003eA focal extender does what a Barlow does, by a different optical route. It multiplies the effective focal length of the telescope by three, which triples the magnification of whatever eyepiece sits behind it and multiplies the working focal ratio by the same factor. A 1000mm f\/8 telescope becomes an effective 3000mm at f\/24. A 24mm eyepiece behaves as an 8mm, taking that telescope from 42x to 125x. A 30mm becomes an effective 10mm at 100x.\u003c\/p\u003e\n\u003cp\u003eWhat separates this from a conventional Barlow is the telecentric design. Explore Scientific describe it as using multiple precision lens elements to deliver light rays that remain parallel to the optical axis, which means the magnification factor stays at 3x regardless of how far the eyepiece or camera sits behind it. A simple negative-lens Barlow does not behave that way: its amplification climbs as the spacing grows, so a diagonal or a filter drawer between Barlow and eyepiece changes the factor. Here it does not.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eWho It's For\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003ePlanetary and lunar observers:\u003c\/strong\u003e 3x turns a comfortable medium-power eyepiece into a high-power one without giving up its eye relief or apparent field.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOwners of ultra-wide 2-inch eyepieces:\u003c\/strong\u003e tripling a 24mm or 30mm ultra-wide gives high magnification with the eye position and field of the original eyepiece, which is not something a short focal-length eyepiece can offer.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePlanetary imagers:\u003c\/strong\u003e a fixed 3x that does not drift with spacing makes the image scale predictable when a camera sits at an arbitrary distance behind it.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAnyone consolidating an eyepiece case:\u003c\/strong\u003e one extender effectively doubles the number of magnifications a set of eyepieces provides.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eKey Features \u0026amp; Design\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e3x magnification factor:\u003c\/strong\u003e triples the effective focal length of the telescope and the magnification of every eyepiece used with it.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTelecentric optical design:\u003c\/strong\u003e multiple precision elements arranged so that emerging rays run parallel to the optical axis, holding the factor at 3x independent of spacing.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEMD (Enhanced Multi-Layer Deposition) coatings:\u003c\/strong\u003e applied to the lens surfaces to raise transmission and suppress internal reflection through what is a multi-element optical train.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEdge-blackened elements:\u003c\/strong\u003e the ground edges of the lenses are blackened so that stray light striking them is absorbed rather than scattered into the image.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e2.0-inch barrel:\u003c\/strong\u003e fits 2-inch focusers and diagonals, and takes 2-inch eyepieces and camera adapters.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e125mm long, 66mm wide:\u003c\/strong\u003e the published physical dimensions.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePublished weight:\u003c\/strong\u003e 22 oz on the specification table, 1.7 lbs. on the product page — both from Explore Scientific.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eOptical Design\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eA conventional Barlow lens is a negative element placed in the converging beam ahead of focus. It slows the convergence, moving the focal plane further back and increasing the effective focal length. The amplification depends on where the negative element sits relative to the new focal plane, which is why a Barlow's marked factor is only accurate at one particular spacing. Insert a star diagonal, a filter drawer or an extension tube behind it and the true factor rises above the number printed on the barrel.\u003c\/p\u003e\n\u003cp\u003eA telecentric design solves that by adding positive elements after the negative group, arranged so that the chief rays leave the assembly parallel to the optical axis rather than diverging. Once the beam is telecentric, moving the eyepiece or the camera sensor backwards changes the back focus but not the amplification. Three times is three times, whether the eyepiece is seated directly in the extender or sitting behind a diagonal.\u003c\/p\u003e\n\u003cp\u003eThat property matters for more than convenience. In imaging, a predictable image scale is what allows a calculated pixel scale to be trusted, and it makes the combination of extender, filter wheel and camera a matter of achieving focus rather than recalculating magnification. The cost of a telecentric group is element count and, therefore, air-to-glass surfaces — which is where the EMD coatings and blackened element edges do their work, and why a telecentric extender is a physically larger object than a simple Barlow of the same nominal power.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eRecommended Uses\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eHigh-power lunar and planetary observing using medium focal-length eyepieces.\u003c\/li\u003e\n\u003cli\u003eSplitting close double stars in apertures that can support the magnification.\u003c\/li\u003e\n\u003cli\u003ePlanetary and lunar imaging, where the fixed amplification keeps image scale predictable.\u003c\/li\u003e\n\u003cli\u003eExtending the useful range of an existing 2-inch eyepiece set without buying short focal lengths.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eCompatibility and Accessory Notes\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eFits 2-inch focusers and diagonals.\u003c\/strong\u003e Eyepieces and camera adapters in the 2-inch format go into the top of it. A 1.25-inch eyepiece can be used through a 2-inch to 1.25-inch adapter, which we stock.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEffective focal length:\u003c\/strong\u003e multiply your telescope's focal length by three. A 750mm Newtonian becomes 2250mm; a 1900mm Maksutov becomes 5700mm.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEffective focal ratio:\u003c\/strong\u003e also multiplied by three. An f\/5 telescope works at f\/15 behind this extender, which is worth knowing for exposure planning in imaging.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEye relief:\u003c\/strong\u003e unchanged. The eyepiece behaves as a shorter focal length while keeping its own eye relief and apparent field, which is the main reason observers use an extender rather than buying a very short eyepiece.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFocus travel:\u003c\/strong\u003e adding 125mm of optical train ahead of the eyepiece shifts the focus position outward. Most 2-inch focusers have the travel for it; a telescope already near the end of its inward travel is the one case where it is worth checking, and we can look at that with you.\u003c\/li\u003e\n\u003c\/ul\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\u003e3x is a large step.\u003c\/strong\u003e On a 200mm telescope, a 24mm eyepiece behind this extender produces a magnification most nights of average seeing will not support. It is an eyepiece-case tool for the steady nights rather than an every-session accessory — and on those nights it is exactly the right thing to reach for.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIt is a substantial piece of hardware.\u003c\/strong\u003e Explore Scientific publish 22 oz on the specification table and 1.7 lbs. on the product page. Either way, with a 2-inch eyepiece on top of it there is real mass hanging off the focuser, so the drawtube tension is worth setting firmly. A focuser upgrade is the answer where the existing one cannot hold it, and we can advise on that.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIt is 2-inch only.\u003c\/strong\u003e Telescopes with 1.25-inch focusers cannot take it directly; the 1.25-inch focal extenders in the same range are the ones that suit those.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eExplore Scientific does not publish the element count or an optical-length figure for this extender,\u003c\/strong\u003e so those rows are absent rather than estimated. For an imaging train where backfocus has to be calculated, send us the camera and spacers you are working with and we will sort the arithmetic out with you.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMagnification has a ceiling set by aperture.\u003c\/strong\u003e Roughly twice the aperture in millimetres is the practical limit, and 3x reaches it quickly in smaller instruments. Pairing the extender with a longer eyepiece rather than a short one is how most observers keep it in useful territory.\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\u003eNo. It goes into the 2-inch focuser or diagonal, and the eyepiece or camera adapter goes into it. Refocusing after fitting it is the only step, and there is nothing to align or adjust.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eHow is this different from a Barlow?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eA Barlow's amplification changes with the distance to the eyepiece, so its marked factor is only correct at one spacing. This is a telecentric design: the rays leave it parallel to the axis, so it stays at 3x whether the eyepiece is seated directly in it or sitting behind a diagonal.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat magnification will I get?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThree times whatever the eyepiece gives on its own. A 24mm eyepiece in a 1000mm telescope gives 42x by itself and 125x through the extender.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDoes it change eye relief?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eNo, and that is the point of using one. The eyepiece keeps its own eye relief and apparent field while behaving as a focal length three times shorter.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWill it work with 1.25-inch eyepieces?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eYes, using a 2-inch to 1.25-inch adapter in the top of it. The extender itself needs a 2-inch focuser or diagonal to sit in.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eIn short: a 2-inch telecentric 3x focal extender with EMD coatings and blackened element edges, holding its amplification constant regardless of spacing and leaving the eyepiece's eye relief untouched. If you would like to know which of your eyepieces will still be useful behind it on your telescope, send us the focal length and aperture and we will run the numbers for you.\u003c\/p\u003e","brand":"Explore Scientific","offers":[{"title":"Default Title","offer_id":44013457834095,"sku":"FE03-020","price":249.95,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/FE03-020_1_1663x__55386.jpg?v=1766553521"},{"product_id":"explore-scientific-2-adapter-for-fffr507x-00","title":"Explore Scientific 2-inch Adapter for FFFR507X-00 Field Flattener Focal Reducer","description":"\u003ch3\u003e\u003cstrong\u003eProduct Overview\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThis is the Explore Scientific 2-inch adapter, item number 510364, which connects Explore Scientific's 3-inch 0.7X Field Flattener Focal Reducer (FFFR507X-00) to a telescope fitted with a 2-inch focuser. It also works in the other direction of the same problem: it allows a 3-inch diagonal to be mounted on a 2-inch focuser drawtube.\u003c\/p\u003e\n\u003cp\u003eExplore Scientific gives its dimensions in the product description rather than in a specification table: 76mm in diameter, 36mm in height, and a weight of .15lb (.08kg). It is a purely mechanical part — there is no glass in it — and its function is to let a 3-inch accessory work on a telescope that was never built with a 3-inch focuser.\u003c\/p\u003e\n\u003cp\u003eThe value of a piece like this is that it changes what an existing telescope can carry without changing the telescope. A 0.7X reducer and flattener is a substantial upgrade to a refractor's imaging performance, and this adapter is what puts one on a tube whose focuser is 2 inches.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eWho It's For\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eOwners of the FFFR507X-00 3-inch 0.7X field flattener focal reducer\u003c\/strong\u003e whose telescope has a 2-inch focuser rather than a 3-inch one.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eImagers upgrading an existing refractor\u003c\/strong\u003e who would rather add a reducer and flattener than replace the focuser or the tube.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOwners of a 3-inch diagonal\u003c\/strong\u003e looking to use it on a telescope with a 2-inch focuser drawtube.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAnyone building an imaging train across two Explore Scientific size standards\u003c\/strong\u003e and needing the mechanical link between them.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eObservers who have moved a flattener or diagonal between telescopes\u003c\/strong\u003e and now need the fitting for the second tube.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eKey Features \u0026amp; Design\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eConnects 3-inch accessories to a 2-inch focuser:\u003c\/strong\u003e the specific job it exists to do, and the reason a 3-inch flattener is not limited to 3-inch focusers.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMade for the FFFR507X-00 0.7X field flattener focal reducer,\u003c\/strong\u003e which is the accessory Explore Scientific names for it.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAlso takes a 3-inch diagonal onto a 2-inch focuser drawtube,\u003c\/strong\u003e so the same part covers a visual as well as an imaging case.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e76mm diameter, 36mm height:\u003c\/strong\u003e a compact connector that adds as little as possible to the optical train.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e.15lb (.08kg) published weight:\u003c\/strong\u003e negligible next to the flattener or diagonal it carries, so it does not change the balance of a setup.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNo optical elements:\u003c\/strong\u003e nothing in the light path to add reflections, scatter or aberration — it is a mechanical coupling only.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eRecommended Uses\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eFitting the Explore Scientific 3-inch 0.7X field flattener focal reducer to a refractor with a 2-inch focuser.\u003c\/li\u003e\n\u003cli\u003eMounting a 3-inch diagonal on a 2-inch focuser drawtube for visual observing.\u003c\/li\u003e\n\u003cli\u003eBuilding an imaging train that spans Explore Scientific's 2-inch and 3-inch fittings.\u003c\/li\u003e\n\u003cli\u003eMoving a 3-inch flattener between a 3-inch-focuser telescope and a 2-inch-focuser telescope as your setup changes.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eCompatibility and Accessory Notes\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eNamed accessory:\u003c\/strong\u003e Explore Scientific specifies this adapter for the FFFR507X-00 3-inch 0.7X Field Flattener Focal Reducer.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFocuser side:\u003c\/strong\u003e it is made for a 2-inch focuser, which covers the majority of refractors above about 80mm.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDiagonal use:\u003c\/strong\u003e Explore Scientific also lists it for mounting a 3-inch diagonal to a 2-inch focuser drawtube.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHeight in the train:\u003c\/strong\u003e the published height is 36mm. Every component in an imaging train consumes part of the available backfocus, so 36mm is the figure to work with when you are adding up the distance from the focuser to the sensor.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eThread and fitting specification:\u003c\/strong\u003e Explore Scientific does not publish the thread sizes or the clamping method for this adapter. If you are matching it to something outside the two applications they name, send us the parts involved and we will confirm the fit with our Explore Scientific representative before you order.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSpacing:\u003c\/strong\u003e the reducer's optimum sensor spacing is a property of the reducer rather than of this adapter, and Explore Scientific does not state how the adapter's 36mm figures into it. Send us the camera and any spacers you have and we will work the numbers through with you.\u003c\/li\u003e\n\u003c\/ul\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\u003eThis is an adapter only.\u003c\/strong\u003e The FFFR507X-00 field flattener focal reducer, the diagonal and any camera-side spacers are separate items. We stock the flattener and can quote the pair together.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIt contains no optics,\u003c\/strong\u003e so it does not change magnification, field or image quality on its own. It changes what mechanically fits, which is a different and equally necessary thing.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIt adds 36mm of length to the optical path.\u003c\/strong\u003e On a visual setup that is rarely an issue; in an imaging train, backfocus is a budget and 36mm is part of it. If you are close to the limit of your focuser travel, that is worth checking first.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eExplore Scientific publishes no thread specification, material or finish detail\u003c\/strong\u003e for this part, so those rows read as not published in the table below rather than being estimated. Anything you need confirmed, we can ask them directly.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIts published weight is .15lb (.08kg),\u003c\/strong\u003e which is the part itself. That figure is worth having when you are totalling up an imaging train, and it is small enough not to affect balance.\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\u003eNo. It is a mechanical connector that goes between the 2-inch focuser and the 3-inch accessory, and it takes seconds to fit. Where care is worthwhile is in the imaging train as a whole, because the 36mm of height it adds is part of the total spacing between the reducer and the camera sensor — and we are glad to work that sum out with you.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat exactly does it connect?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eExplore Scientific lists two applications: the 3-inch 0.7X Field Flattener Focal Reducer (FFFR507X-00) onto a telescope with a 2-inch focuser, and a 3-inch diagonal onto a 2-inch focuser drawtube.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDoes it include the field flattener?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eNo. This listing is the adapter alone. The FFFR507X-00 is a separate item, and we can put the two together on one order if that is easier.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWill it change the image?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eNot by itself — it has no glass in it. The reducer does the optical work; this part is what lets the reducer attach.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eHow much room does it take up?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003e76mm across and 36mm tall, at .15lb (.08kg). The 36mm is the number that matters when you are counting backfocus.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWill it fit my telescope?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eIf your telescope has a 2-inch focuser, that is the side this adapter is made for. For anything unusual, send us the make and model of the telescope and the accessory you want to attach and we will confirm it before you order.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eIn short: a 76mm by 36mm, .15lb mechanical adapter that puts Explore Scientific's 3-inch 0.7X field flattener focal reducer — or a 3-inch diagonal — onto a telescope with a 2-inch focuser. If you tell us the telescope, the camera and the accessories you are joining up, we will check the spacing and the fit with you before anything ships.\u003c\/p\u003e","brand":"Explore Scientific","offers":[{"title":"Default Title","offer_id":44013539491951,"sku":"510364","price":138.95,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/0510364_1_1800x1800__63738.jpg?v=1766555641"},{"product_id":"explore-scientific-field-flattener-f-5-to-f-7","title":"Explore Scientific Field Flattener f\/5 to f\/7","description":"\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(29, 29, 29); font-family: \" nunito 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);\"\u003eThis is a field flattener for refractor-type telescopes with a focal ratio of f\/5 to f\/7\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);\"\u003eCauses no change to the telescope focal length\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);\"\u003e2-inch barrel to easily attach to a two-inch focuser\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);\"\u003eFully multi-coated optics\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);\"\u003eT-ring thread on the device so a T-ring can be used to easily attach a DSLR camera or a dedicated astrocamera\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);\"\u003e38 mm of clear aperture\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);\"\u003eRequires 55mm (+\/-2) of back focus\/spacing between the device and the camera sensor\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);\"\u003ePremium high glossy anodizing finish\u003c\/li\u003e\n\u003c\/ul\u003e\u003cdiv\u003e\u003cspan style=\"font-family: \" nunito sans sans-serif color: rgb\u003e\u003cdiv\u003eFits the following Explore Scientific telescopes:\u003c\/div\u003e\n\u003cdiv\u003eDAR1020765-01\u003c\/div\u003e\n\u003cdiv\u003eDAR127065-02\u003c\/div\u003e\n\u003cdiv\u003eDAR152065-01\u003c\/div\u003e\n\u003cdiv\u003eES-ED0806-02\u003c\/div\u003e\n\u003cdiv\u003eES-ED10207-02\u003c\/div\u003e\n\u003cdiv\u003eFCD100-0806-01\u003c\/div\u003e\n\u003cdiv\u003eFCD100-10207-02\u003c\/div\u003e\u003c\/span\u003e\u003c\/div\u003e","brand":"Explore Scientific","offers":[{"title":"Default Title","offer_id":44013865173103,"sku":"ES-FF2F5\/F7","price":193.95,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/ES-FF2F5_F7__85161.jpg?v=1766564971"},{"product_id":"explore-scientific-0-8x-focal-reducer-f5-to-f7-refractors","title":"Explore Scientific 0.8x Focal Reducer for f\/5 to f\/7 Refractors with 55mm Back Spacing","description":"\u003ch2\u003eProduct Overview\u003c\/h2\u003e\u003cp\u003eThe Explore Scientific ES-FR0.8x is a two-element 0.8x focal reducer made for refractors working between roughly f\/5 and f\/7. It multiplies your telescope's focal length by 0.8, which shortens the focal length, speeds up the focal ratio and widens the field your camera records. Explore Scientific gives two worked examples: a 480mm f\/6 refractor becomes 384mm at f\/4.8, and a 714mm f\/7 refractor becomes 571mm at f\/5.6. It threads into a standard 42mm T-ring and works at 55mm of back spacing, plus or minus 2mm, which is the same nominal spacing used by most T-ring and camera combinations in astrophotography.\u003c\/p\u003e\u003ch2\u003eWho It's For\u003c\/h2\u003e\u003cp\u003eThis is for the imager who likes their refractor but wants more sky in the frame and shorter exposures to get it. A reducer solves a framing and speed problem: the target does not fit, or it fits so tightly that there is nothing left for composition, or the sub-exposures are long enough that guiding errors and satellite trails start eating your night. Dropping from f\/6 to f\/4.8 collects the same signal in noticeably less time, and the wider field turns large emission nebulae and open clusters from crops into portraits.\u003c\/p\u003e\u003cp\u003eIt is worth being blunt about what this is not. A focal reducer and a coma corrector are not interchangeable, and buying one when you needed the other leaves you with the wrong tool entirely. A coma corrector fixes off-axis coma, the seagull-shaped stars at the edge of the frame that fast Newtonian reflectors produce, and it does not meaningfully widen your field. This reducer is the opposite errand: it is for refractors, it changes focal length and focal ratio, and it is about framing and exposure time rather than repairing a specific aberration of a mirror telescope. If you shoot with a fast Newtonian, you want a coma corrector. If you shoot with an f\/5 to f\/7 refractor and want a wider, faster field, you want this.\u003c\/p\u003e\u003ch2\u003eKey Features and Design\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003e0.8x reduction factor, shortening focal length and speeding the focal ratio by the same proportion\u003c\/li\u003e\n\u003cli\u003eTwo-element optical design\u003c\/li\u003e\n\u003cli\u003eBack spacing of 55mm, plus or minus 2mm, the standard working distance for most T-ring and camera stacks\u003c\/li\u003e\n\u003cli\u003eAccepts a standard 42mm T-ring, so it drops into the usual imaging train rather than demanding proprietary adapters\u003c\/li\u003e\n\u003cli\u003eIntended for refractors in the f\/5 to f\/7 range\u003c\/li\u003e\n\u003cli\u003eExplore Scientific publishes worked conversions of 480mm to 384mm, taking f\/6 to f\/4.8, and 714mm to 571mm, taking f\/7 to f\/5.6\u003c\/li\u003e\n\u003cli\u003eListed by Explore Scientific for the ES-ED0806-02, ES-ED10207-02, FCD100-0806-02, FCD100-10207-02 and FCD100-10207-CF-01 telescopes\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch2\u003eOptical Design\u003c\/h2\u003e\u003cp\u003eA focal reducer sits in the converging light cone behind the objective and adds negative-to-positive optical power that brings the focus in closer, shortening the effective focal length. Because the aperture has not changed, a shorter focal length means a smaller focal ratio number, and the image scale on the sensor shrinks by the same 0.8 factor, so more sky lands on the same chip. The illumination per square millimetre of sensor rises as the square of the change in focal ratio, which is why a 0.8x reducer is often described as making a telescope roughly one and a half times faster in exposure terms. The 55mm back spacing is not a suggestion. Reducers only deliver their designed correction at one working distance, and drifting away from it changes the effective reduction and pushes stars in the corners out of round. Explore Scientific quotes a tolerance of plus or minus 2mm, which is tight enough that you should measure your spacers rather than estimate them. The two-element construction keeps the glass count and the light loss low, and it also keeps the reducer short enough not to swallow an unreasonable amount of your focuser's back focus.\u003c\/p\u003e\u003ch2\u003eRecommended Uses\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003eWide-field deep-sky imaging with an f\/5 to f\/7 apochromatic or ED refractor\u003c\/li\u003e\n\u003cli\u003eShortening exposure times on faint, extended targets such as large emission nebulae\u003c\/li\u003e\n\u003cli\u003eFraming large objects that do not fit the native field of your refractor\u003c\/li\u003e\n\u003cli\u003eReducing the demand on your guiding by cutting sub-exposure length\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch2\u003eCompatibility and Accessory Notes\u003c\/h2\u003e\u003cp\u003eExplore Scientific lists this reducer for its ES-ED0806-02, ES-ED10207-02, FCD100-0806-02, FCD100-10207-02 and FCD100-10207-CF-01 refractors, and describes it more generally as suiting f\/5 to f\/7 refractors. You will need a 42mm T-ring for your camera body, and you will need to build the imaging train so that the sensor sits 55mm behind the reducer, which usually means the T-ring plus one or more spacer rings depending on your camera's flange distance. Cooled astronomy cameras with built-in filter drawers and off-axis guiders complicate that arithmetic, so it is worth working out the numbers before you order. Send us your telescope and camera model and our team in Bolton will confirm the spacing you need and whether this reducer suits your particular optical train.\u003c\/p\u003e\u003ch2\u003eGood to Know Before You Order\u003c\/h2\u003e\u003cp\u003eNo T-ring, spacers or camera adapters are included, and Explore Scientific does not publish a packing list for this item. This reducer is designed for refractors in a specific focal ratio band, and it is not a coma corrector for Newtonian reflectors, nor is it a substitute for one. The 55mm spacing tolerance of plus or minus 2mm is worth respecting, and if your back focus budget is already tight you should confirm the numbers before committing. Explore Scientific publishes no shipping weight for this item, so we are confirming it on our own scales before the listing goes live. That is why it is currently unpublished. Contact us and we will give you a shipping figure for your address.\u003c\/p\u003e\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\u003cp\u003e\u003cstrong\u003eWill this correct coma in my Newtonian?\u003c\/strong\u003e No. Coma is an off-axis aberration of the parabolic mirror in a reflector and needs a coma corrector. This is a focal reducer for refractors, and it changes focal length and field width rather than repairing coma.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat does 55mm back spacing actually mean?\u003c\/strong\u003e It is the distance from the reducer's shoulder to your camera's sensor. Get it right and the correction is as designed. Drift outside the plus or minus 2mm tolerance and the reduction factor shifts and corner stars start to elongate.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eCan I use it visually?\u003c\/strong\u003e It is designed and specified as an imaging accessory working to a 42mm T-ring at a defined sensor distance, so visual use is not what Explore Scientific specifies for it. If you want a wider visual field, a longer focal length eyepiece is the simpler answer.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eDoes it work on telescopes outside the f\/5 to f\/7 range?\u003c\/strong\u003e Explore Scientific specifies f\/5 to f\/7 refractors and names five of its own models. Outside that band the correction may not hold across the field. Ask us and we will check your telescope against the specification.\u003c\/p\u003e\u003ch2\u003eBottom Line\u003c\/h2\u003e\u003cp\u003eIf you image with an f\/5 to f\/7 refractor and keep running out of frame, this two-element 0.8x reducer widens the field and speeds the system in one step, using standard 42mm T-ring threads and 55mm back spacing. Just make sure a reducer is what your telescope needs, because a fast Newtonian wants a coma corrector instead. Contact our team in Bolton and we will confirm the fit and the spacing for your setup.\u003c\/p\u003e","brand":"Explore Scientific","offers":[{"title":"Default Title","offer_id":53958593970287,"sku":"ES-FR0.8x","price":193.95,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/ES-FR0.8X_1_7c74a6f1-4013-4ce6-9df0-3c958a8967b3.jpg?v=1785960612"},{"product_id":"explore-scientific-hr-variable-coma-corrector-no-adapters","title":"Explore Scientific HR Variable Coma Corrector 2-inch, NO Camera Adapters Included","description":"\u003ch2\u003eProduct Overview\u003c\/h2\u003e\u003cp\u003eThe Explore Scientific HR Variable Coma Corrector is a 2-inch corrector for Newtonian reflectors, designed by the optical designer Harrie Rutten and EMC coated to hold down internal reflections. This is item HRCC02-01, the version supplied \u003cstrong\u003ewithout\u003c\/strong\u003e camera adapters. In Explore Scientific's own words, “this model does not come with the adapters that allow for a direct screw-on connection to a camera.” Published figures are 1 lb (0.45 kg), 69.3 mm in diameter and 147.2 mm tall.\u003c\/p\u003e\u003cp\u003eThe optics are the same as the HRCC02-00 version. The difference is what is in the box, and the price reflects it. If you want to screw a camera straight onto the corrector, buy the HRCC02-00 instead — we stock both.\u003c\/p\u003e\u003ch2\u003eWho It's For\u003c\/h2\u003e\u003cp\u003eVisual observers with fast parabolic Newtonians, and imagers who already own the thread adapters they need. Coma is inherent to the paraboloid: it grows with distance from the optical axis and worsens sharply as the focal ratio drops, so an f\/4 mirror shows comet-tailed stars well inside the field of a wide-angle eyepiece. This corrector is the standard remedy and Explore Scientific specifies it for fast mirrors from around f\/3.9.\u003c\/p\u003e\u003cp\u003eBuying this version is the right call if you are using it visually with 2-inch eyepieces, or if you have a drawer of M42 and M48 adapters already and would rather not pay for another set. If neither is true, the HRCC02-00 with adapters included usually works out cheaper than buying this and sourcing adapters afterwards.\u003c\/p\u003e\u003ch2\u003eKey Features \u0026amp; Design\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003e2-inch coma corrector for parabolic Newtonian reflectors, specified for fast mirrors from around f\/3.9\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCamera adapters are not included\u003c\/strong\u003e — no direct screw-on camera connection out of the box\u003c\/li\u003e\n\u003cli\u003eOptical design by Harrie Rutten\u003c\/li\u003e\n\u003cli\u003eEMC coating to suppress internal reflections and ghosting on bright stars\u003c\/li\u003e\n\u003cli\u003eVariable spacer with markings, so the corrector can be set for different telescopes\u003c\/li\u003e\n\u003cli\u003e1 lb (0.45 kg), 69.3 mm diameter, 147.2 mm tall\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch2\u003eOptical Design\u003c\/h2\u003e\u003cp\u003eA parabolic mirror focuses sharply on axis and nowhere else. Off axis, rays from different zones of the mirror land in slightly different places and the resulting flare is coma — stars grow a one-sided tail pointing away from field centre, lengthening the further out you look. The effect scales roughly as the inverse square of the focal ratio, so halving the f-number quadruples the coma. That is why the fast Newtonian you want for wide fields is also the one that shows the aberration worst.\u003c\/p\u003e\u003cp\u003eThe corrector sits in the converging beam ahead of focus and applies an equal and opposite aberration, pulling those tails back into points. Its distance from the eyepiece field stop or sensor determines how completely it does so, which is why the spacer is marked rather than fixed — different telescopes want different spacings and the markings let you find yours and return to it. The EMC coating earns its place because a multi-element group sitting in a converging beam is otherwise a good source of ghost images from bright stars.\u003c\/p\u003e\u003ch2\u003eRecommended Uses\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003eWide-field visual observing in a fast Newtonian or Dobsonian, sharpening stars at the field edge\u003c\/li\u003e\n\u003cli\u003eDeep-sky imaging where you already own the M42 or M48 adapters the connection needs\u003c\/li\u003e\n\u003cli\u003eStar parties and outreach with fast mirrors, where edge-of-field coma is most obvious to newcomers\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch2\u003eCompatibility and Accessory Notes\u003c\/h2\u003e\u003cp\u003eThis corrects coma; it is not a focal reducer and will not shorten your focal length or speed up your system. It is designed for parabolic primary mirrors — Newtonians and Dobsonians — not refractors, which want a field flattener instead. It fits a 2-inch focuser and needs enough in-travel to reach focus with the corrector in place. For camera use you will need to add the thread adapter yourself: Explore Scientific points to a T2 camera adapter, and their 2-inch to 1.25-inch adapter (item 510365) is a related part we also stock. Tell us your camera and telescope and we will work out which adapter and what spacing you need before you order.\u003c\/p\u003e\u003ch2\u003eGood to Know Before You Order\u003c\/h2\u003e\u003cp\u003eRead the title twice before you buy — this is the corrector on its own. There is no camera adapter in the box, so a DSLR or astro camera cannot screw directly onto it as supplied. The HRCC02-00 version includes both M42x0.75 and M48x0.75 adapters and typically costs less than this listing plus adapters bought separately, so it is the better value if imaging is your intention. Reaching focus is the other common snag: adding a corrector moves the focal plane, and some Newtonians need a low-profile focuser to get there. We can check that with you.\u003c\/p\u003e\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\u003cp\u003e\u003cstrong\u003eWhy is this cheaper than the other Explore Scientific coma corrector?\u003c\/strong\u003e Because the camera adapters are not included. The corrector itself is the same — same Harrie Rutten design, same EMC coating, same marked spacer.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eCan I still use it with a camera?\u003c\/strong\u003e Yes, once you add the right thread adapter. It is not supplied here, and buying it separately usually costs more than the gap to the HRCC02-00 version. Ask us and we will price both ways for you.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWill it work on my f\/5 Dobsonian?\u003c\/strong\u003e Yes — it is designed for parabolic Newtonians and specified for fast mirrors from around f\/3.9. Reaching focus is the thing to check, not the optics.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eDoes it change my focal length?\u003c\/strong\u003e No. It corrects coma and leaves the focal ratio alone. A focal reducer is a different product.\u003c\/p\u003e\u003ch2\u003eBottom Line\u003c\/h2\u003e\u003cp\u003eThe Harrie Rutten HR coma corrector, corrector only, at a lower price than the adapter-equipped version. The right buy for visual observers and for imagers who already own their adapters. If a camera is in your plans and your adapter drawer is empty, take the HRCC02-00 instead — our Bolton team will tell you honestly which one suits you.\u003c\/p\u003e","brand":"Explore Scientific","offers":[{"title":"Default Title","offer_id":53958612811887,"sku":"HRCC02-01","price":193.95,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/HRCC02-00_1_57f89e7a-03ee-46e8-b2ee-7841ed531341.jpg?v=1785960673"},{"product_id":"explore-scientific-m48-adapter-3-inch-field-flattener-0-7x-reducer","title":"Explore Scientific M48 x 0.75 Camera Adapter for 3-inch Field Flattener and 0.7x Focal Reducer","description":"\u003ch2\u003eProduct Overview\u003c\/h2\u003e\u003cp\u003eThis is the wide-thread camera adapter for Explore Scientific's 3-inch Field Flattener and 0.7x Focal Reducer, the corrector usually shortened to FFFR (item FFFR507X-00). The FFFR ships with an M42 x 0.75 adapter for CCD and DSLR cameras; this part replaces it with an M48 x 0.75 thread, opening up the camera end of the corrector. Explore Scientific states plainly that it must be purchased separately from the FFFR, and publishes a weight of 0.15 lb (0.08 kg). Vendor item number M48-0750.7x.\u003c\/p\u003e\u003ch2\u003eWho It's For\u003c\/h2\u003e\u003cp\u003eThis exists to solve one specific and frustrating problem: you bought a focal reducer to get a wider, faster field, and then discovered the corners of that wider field were dim. The 0.7x FFFR does its job well, compressing the image circle and dropping the focal ratio so that a given exposure goes further, but the standard M42 adapter that comes in the box presents a throat of only about 39 mm to the camera. A full-frame sensor measures 43.3 mm across the diagonal. The reducer is delivering a field the adapter behind it cannot pass, and the result is corner falloff that no amount of flat framing fully rescues.\u003c\/p\u003e\u003cp\u003eSwapping in this M48 x 0.75 adapter widens that final aperture so the corrector can actually deliver what it was designed to deliver. If you are running an APS-C or smaller sensor you may never need it, since a 28 mm diagonal fits through an M42 throat without complaint. If you have moved to a full-frame body, or you are running the FFFR on a fast scope where corner illumination is already working hard, this is the part that stops the adapter from being the limiting element in your imaging train. It is also the right choice if the rest of your train is already standardised on M48 and you would rather not stack step rings behind an expensive corrector.\u003c\/p\u003e\u003ch2\u003eKey Features \u0026amp; Design\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003eM48 x 0.75 camera thread, the wide standard used by Explore Scientific's M48 camera rings and 2-inch filters\u003c\/li\u003e\n\u003cli\u003eDirect replacement for the M42 x 0.75 CCD camera adapter supplied as standard with the 3-inch Field Flattener and 0.7x Focal Reducer\u003c\/li\u003e\n\u003cli\u003ePurpose-made for the FFFR507X-00, so it mates with the corrector's own fitting rather than relying on a stack of generic step rings\u003c\/li\u003e\n\u003cli\u003eRemoves the narrow M42 throat as the bottleneck in a reduced, wide-field imaging train\u003c\/li\u003e\n\u003cli\u003ePublished weight of 0.15 lb (0.08 kg), adding nothing meaningful to the load behind the focuser\u003c\/li\u003e\n\u003cli\u003eAll-threaded connection at both ends, so there is no compression ring to slip and no camera rotation mid-sequence\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch2\u003eOptical and Mechanical Design\u003c\/h2\u003e\u003cp\u003eA focal reducer works by shortening the effective focal length, which shrinks the image scale and simultaneously widens the illuminated circle projected onto the sensor. The 0.7x factor means a scope at f\/7 becomes roughly f\/4.9, and the field being poured onto the sensor grows accordingly. That is precisely why the camera-side aperture matters more after a reducer than before one: you have deliberately made the light cone wider and shallower, and the last mechanical opening it passes through now sets your corner illumination. An M42 x 0.75 thread caps that opening at roughly 39 mm; M48 x 0.75 raises it well past the 43.3 mm full-frame diagonal. The second half of the design question is spacing. Every corrector has a designed distance from its rear element to the sensor, and missing it produces elongated or misshapen stars in the corners — the same symptom people often misread as collimation or tracking error. Because Explore Scientific presents this as a swap for the adapter the FFFR already ships with, it is intended to sit in the same place in the train rather than to change the corrector's spacing. Explore Scientific does not publish a light path length for it, so if you are working to an exact back focus figure, treat that number as something to confirm rather than assume.\u003c\/p\u003e\u003ch2\u003eRecommended Uses\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003eFull-frame DSLR, mirrorless or CCD imaging behind the Explore Scientific 3-inch Field Flattener and 0.7x Focal Reducer\u003c\/li\u003e\n\u003cli\u003eWide-field deep-sky work where corner illumination and flat field both matter\u003c\/li\u003e\n\u003cli\u003eStandardising an existing imaging train on M48 x 0.75 to remove step rings from behind the corrector\u003c\/li\u003e\n\u003cli\u003eReplacing the supplied M42 adapter after upgrading from a crop-sensor body to full frame\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch2\u003eCompatibility and Accessory Notes\u003c\/h2\u003e\u003cp\u003eThis is a dedicated part for the Explore Scientific 3-inch Field Flattener and 0.7x Focal Reducer, FFFR507X-00. It is not a general-purpose thread ring, and that distinction is worth holding onto, because Explore Scientific also sells a general M48-to-M42 reduction adapter that sounds similar and does something quite different — that one bridges the two standards anywhere in a train, while this one is the camera-side fitting for one particular corrector. If you do not own the FFFR, this is almost certainly not the part you want. On the camera side you will need something with an M48 x 0.75 thread: Explore Scientific's M48 camera rings for Canon EOS and Nikon are the natural partners, and the M48 junction will also accept a 2-inch filter, since 2-inch astrophotography filters are cut to M48 x 0.75. Bear in mind that the ring only helps if it is the narrowest point you have fixed; a T2 ring left further down the chain will reimpose the same bottleneck. Spacing and fit behind a corrector are genuinely model-dependent, so tell our team in Bolton which camera and which scope you are running the FFFR on and we will confirm the combination before you order.\u003c\/p\u003e\u003ch2\u003eGood to Know Before You Order\u003c\/h2\u003e\u003cp\u003eThe most important thing to understand is that this is sold separately from the FFFR and is not an upgrade you receive with it — Explore Scientific says so directly on their own page. Buying the corrector does not get you this adapter. The camera ring is not included either, nor is any filter. Explore Scientific does not publish dimensions or a light path length for this item, only the 0.15 lb weight, so if your imaging train is tuned to a specific back focus we would rather measure it here than have you discover a discrepancy under clear skies; contact us and we will do that. Finally, this widens the camera end of the corrector only. It cannot improve illumination that was already lost further up the optical train, and it does not change the FFFR's optical performance in any way — it simply stops the mechanics from throwing away the field the glass is producing.\u003c\/p\u003e\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\u003cp\u003e\u003cstrong\u003eDoes the 3-inch Field Flattener and 0.7x Focal Reducer already come with this?\u003c\/strong\u003e No. The FFFR ships with an M42 x 0.75 adapter for CCD cameras. This M48 version replaces it and must be bought separately, which Explore Scientific states explicitly.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eDo I need it if I shoot an APS-C camera?\u003c\/strong\u003e Probably not. A crop sensor has a diagonal of around 28 mm, comfortably inside what the standard M42 adapter passes. The M48 upgrade earns its place with full-frame sensors, or if you want the whole train on one thread standard.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eIs this the same as the M48 to M42 reduction adapter?\u003c\/strong\u003e No. That is a general-purpose ring for joining the two thread standards anywhere in an imaging train. This is the camera-side adapter made specifically for the FFFR507X-00 corrector.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat do I screw onto the M48 end?\u003c\/strong\u003e An M48 x 0.75 camera ring for your body — Explore Scientific makes them for Canon EOS and Nikon — or a 2-inch filter, since 2-inch filters share the M48 x 0.75 thread.\u003c\/p\u003e\u003ch2\u003eBottom Line\u003c\/h2\u003e\u003cp\u003eIf you own the Explore Scientific 3-inch Field Flattener and 0.7x Focal Reducer and a full-frame camera, this is the adapter that lets the corrector finish the job it started, by taking the narrow M42 throat out of the light path. It is a small, purpose-built part and not a general thread ring, so make sure the FFFR is what you are fitting it to. Our team in Bolton will confirm the spacing and the camera-side parts with you before you order.\u003c\/p\u003e","brand":"Explore Scientific","offers":[{"title":"Default Title","offer_id":53958709313647,"sku":"M48-0750.7x","price":50.95,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/M48-0750.7x_1.jpg?v=1785960903"}],"url":"https:\/\/ontariotelescope.com\/collections\/fr-explore-scientific.oembed","provider":"Ontario Telescope and Accessories","version":"1.0","type":"link"}