{"title":"Coma Correctors","description":"\u003cp\u003eComa Correctors from every brand we carry. Part of \u003ca href=\"\/collections\/flatteners-and-reducers\"\u003eFlatteners, Reducers \u0026amp; Correctors\u003c\/a\u003e.\u003c\/p\u003e","products":[{"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":"baader-multi-purpose-coma-corrector","title":"Baader Multi Purpose Coma Corrector","description":"\u003ch3 style=\"box-sizing: border-box; margin: 0px 0px 0.75em; padding: 0px; font-size: 1.5em; color: rgb(235, 2, 53); font-family: \" open sans sans-serif optimizespeed rgb line-height:=\"\" text-rendering:=\"\" background-color:=\"\"\u003eBaader MPCC Mark III - Multi Purpose Newton Coma Corrector\u003c\/h3\u003e\u003ch4 style=\"box-sizing: border-box; margin: 0px 0px 0.75em; padding: 0px; font-size: 1.2em; color: rgb(99, 99, 99); font-family: \" open sans sans-serif optimizespeed rgb line-height:=\"\" text-rendering:=\"\" background-color:=\"\"\u003eThe only coma corrector for Newton telescopes, that neither reduces the focal length nor the image field of your telescope\u003c\/h4\u003e\u003cdiv class=\"leftImage\" style=\"box-sizing: border-box; margin: 0px 15px 1em 0px; padding: 0px; font-family: \" open sans sans-serif center top left rgb text-align:=\"\" vertical-align:=\"\" float:=\"\" clear:=\"\" color:=\"\" font-size:=\"\" background-color:=\"\" width:=\"\"\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/mpcc-III-01-gross_8832a66f-428b-4226-afe5-fae3c998f9e0.jpg?v=1766551470\" alt=\"Baader MPCC Mark III - Multi Purpose Newton Coma Correktor T2\" title=\"Baader MPCC Mark III - Multi Purpose Newton Coma Correktor T2\" width=\"250\" style=\"box-sizing: border-box; margin: 0px; padding: 0px; border: none; display: block;\"\u003e\u003c\/div\u003e\u003cdiv class=\"rightImage\" style=\"box-sizing: border-box; margin: 0px 0px 1em 15px; padding: 0px; font-family: \" open sans sans-serif center top right rgb text-align:=\"\" vertical-align:=\"\" float:=\"\" clear:=\"\" color:=\"\" font-size:=\"\" background-color:=\"\" width:=\"\"\u003e\n\u003ca class=\"image-popup\" href=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/mpcc_07_goss_1011cddf-6b46-495e-ae7d-d716c00036ab.jpg?v=1766551474\" target=\"_blank\" style=\"box-sizing: border-box; margin: 0px; padding: 0px; touch-action: manipulation; color: rgb(235, 2, 53); text-decoration: none; transition: all 0.2s;\"\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/mpcc_07_goss_1011cddf-6b46-495e-ae7d-d716c00036ab.jpg?v=1766551474\" alt=\"MPCC MIII\" title=\"MPCC MIII\" width=\"300\" style=\"box-sizing: border-box; margin: 0px; padding: 0px; border: none; display: block;\"\u003e\u003c\/a\u003e\u003cdiv class=\"imageCaption\" style=\"box-sizing: border-box; margin: 0px; padding: 0.5em 0.5em 0px; clear: both; font-size: 0.846em;\"\u003eSingle parts of the MPCC MIII for visual + photographic use\u003cbr style=\"box-sizing: border-box; margin: 0px; padding: 0px;\"\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\u003cp style=\"box-sizing: border-box; margin: 0px 0px 1.5em; padding: 0px; font-family: \" open sans sans-serif rgb color:=\"\" font-size:=\"\" background-color:=\"\"\u003eLarge parabolic mirrors are perfectly apt for Deep Sky imaging since they deliver a very large field and enable very short exposure times. However this comes at the price of off axis coma and some residual astigmatism. Coma will distort off axis stars into \"comets\" which effectively reduces the usable field considerably. Many companys offer various lens systems as solution to counteract coma, most at the downside of increasing the original focal length and reducing the field of view. An f4 optics may become an f4.5\u003c\/p\u003e\u003cp style=\"box-sizing: border-box; margin: 0px 0px 1.5em; padding: 0px; font-family: \" open sans sans-serif rgb color:=\"\" font-size:=\"\" background-color:=\"\"\u003eThe Multi Purpose Coma Corrector Mark III eliminates coma across the full photographic field without manipulating the focal length. The proprietory lens design has our Phantom Group  wideband multicoating on all air to glass lens surfaces. This treatment delivers highest transmission combined with lowest amount of scatter and reflections across a very wide spectral range from UV to NIR. The original MPCC had been designed for an f\/ratio of f4.5 to f6. The new Mark III however works exceptionally well even down to f3.5. Stars remain pinpoints across the field and the visual use likewise is made much easier - with the help of the 2\" (M48) male filter thread at the eyepiece facing side.\u003c\/p\u003e\u003cp style=\"box-sizing: border-box; margin: 0px 0px 1.5em; padding: 0px; font-family: \" open sans sans-serif rgb color:=\"\" font-size:=\"\" background-color:=\"\"\u003eThe MPCC III is designed to be the most variable coma corrector in the market today. It mounts into every 2\" focuser and fits CCD-filter wheels and off axis guiders of various manufacturers.\u003c\/p\u003e\u003cp style=\"box-sizing: border-box; margin: 0px 0px 1.5em; padding: 0px; font-family: \" open sans sans-serif rgb color:=\"\" font-size:=\"\" background-color:=\"\"\u003eWith the optional T-Spacer (# 245 8405) you will be able to couple the Mark III directly to the Baader Protective Canon DSLR adapter - with or without mounted various filter.\u003c\/p\u003e\u003cp style=\"box-sizing: border-box; margin: 0px 0px 1.5em; padding: 0px; font-family: \" open sans sans-serif rgb color:=\"\" font-size:=\"\" background-color:=\"\"\u003eThe MPCC MIII Version for either visuell or photographic use contains of the following parts, otherwise see the common description for the MPCC above.\u003c\/p\u003e\u003ch3 style=\"box-sizing: border-box; margin: 0px 0px 0.75em; padding: 0px; font-size: 1.5em; color: rgb(235, 2, 53); font-family: \" open sans sans-serif optimizespeed rgb line-height:=\"\" text-rendering:=\"\" background-color:=\"\"\u003eTechnical data of MPCC Mark III\u003c\/h3\u003e\u003cul style=\"box-sizing: border-box; margin: 0px 0px 1em; padding: 0px; list-style-position: initial; list-style-image: initial; font-family: \" open sans sans-serif rgb color:=\"\" font-size:=\"\" background-color:=\"\"\u003e\n\u003cli style=\"box-sizing: border-box; margin: 0.5em 0px 0px 1.5em; padding: 0px;\"\u003eno change in focal length or field size, an f4 Newtonian remains f4.\u003c\/li\u003e\n\u003cli style=\"box-sizing: border-box; margin: 0.5em 0px 0px 1.5em; padding: 0px;\"\u003enewly calculated lens system - designed for an unvignetted field down to f3.5\u003c\/li\u003e\n\u003cli style=\"box-sizing: border-box; margin: 0.5em 0px 0px 1.5em; padding: 0px;\"\u003emaximum sharpness across the field - without center soft spot (as reported of other)\u003c\/li\u003e\n\u003cli style=\"box-sizing: border-box; margin: 0.5em 0px 0px 1.5em; padding: 0px;\"\u003eaccepts T-2(M42x0.75) and\/or 2\"(M48x0.75) threaded photographic- or visual-adapters\u003c\/li\u003e\n\u003cli style=\"box-sizing: border-box; margin: 0.5em 0px 0px 1.5em; padding: 0px;\"\u003e2\" stopping collar removable for increase in backfocus\u003c\/li\u003e\n\u003cli style=\"box-sizing: border-box; margin: 0.5em 0px 0px 1.5em; padding: 0px;\"\u003eFor photographic and visual use\u003c\/li\u003e\n\u003cli style=\"box-sizing: border-box; margin: 0.5em 0px 0px 1.5em; padding: 0px;\"\u003eeasy to use\u003c\/li\u003e\n\u003cli style=\"box-sizing: border-box; margin: 0.5em 0px 0px 1.5em; padding: 0px;\"\u003eexceptional price\/performance ratio\u003c\/li\u003e\n\u003cli style=\"box-sizing: border-box; margin: 0.5em 0px 0px 1.5em; padding: 0px;\"\u003ePhantom Group  multicoated for maximum transmission and freedom from reflections from UV to NIR\u003c\/li\u003e\n\u003cli style=\"box-sizing: border-box; margin: 0.5em 0px 0px 1.5em; padding: 0px;\"\u003eOptional adapter for direct coupling of the MPCC III directly onto the Baader CANON EOS protective T-ring\u003c\/li\u003e\n\u003cli style=\"box-sizing: border-box; margin: 0.5em 0px 0px 1.5em; padding: 0px;\"\u003e44mm clear aperture when using the M48(2\") filter-tread or the Protective T-ring with optional adapter\u003c\/li\u003e\n\u003c\/ul\u003e\u003cdiv class=\"leftImage\" style=\"box-sizing: border-box; margin: 0px 15px 1em 0px; padding: 0px; font-family: \" open sans sans-serif center top left rgb text-align:=\"\" vertical-align:=\"\" float:=\"\" clear:=\"\" color:=\"\" font-size:=\"\" background-color:=\"\" width:=\"\"\u003e\u003ca class=\"image-popup\" href=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/mpcc-III-02-gross_63e1bf8b-ef23-43ff-a6e3-f6d3543a38e7.jpg?v=1766551478\" target=\"_blank\" style=\"box-sizing: border-box; margin: 0px; padding: 0px; touch-action: manipulation; color: rgb(235, 2, 53); text-decoration: none; transition: all 0.2s;\"\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/mpcc-III-02-gross_63e1bf8b-ef23-43ff-a6e3-f6d3543a38e7.jpg?v=1766551478\" alt=\"Koma Korrektor\" title=\"Koma Korrektor\" width=\"250\" style=\"box-sizing: border-box; margin: 0px; padding: 0px; border: none; display: block;\"\u003e\u003c\/a\u003e\u003c\/div\u003e\u003cdiv class=\"leftImage\" style=\"box-sizing: border-box; margin: 0px 15px 1em 0px; padding: 0px; font-family: \" open sans sans-serif center top left none rgb text-align:=\"\" vertical-align:=\"\" float:=\"\" clear:=\"\" color:=\"\" font-size:=\"\" background-color:=\"\" width:=\"\"\u003e\u003ca class=\"image-popup\" href=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/mpcc-III-03-gross_9392f11e-4298-41f8-bcbf-31e78e638bb3.jpg?v=1766551482\" target=\"_blank\" style=\"box-sizing: border-box; margin: 0px; padding: 0px; touch-action: manipulation; color: rgb(235, 2, 53); text-decoration: none; transition: all 0.2s;\"\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/mpcc-III-03-gross_9392f11e-4298-41f8-bcbf-31e78e638bb3.jpg?v=1766551482\" alt=\"Koma Korrektor\" title=\"Koma Korrektor\" width=\"250\" style=\"box-sizing: border-box; margin: 0px; padding: 0px; border: none; display: block;\"\u003e\u003c\/a\u003e\u003c\/div\u003e\u003cdiv class=\"leftImage\" style=\"box-sizing: border-box; margin: 0px 15px 1em 0px; padding: 0px; font-family: \" open sans sans-serif center top left none rgb text-align:=\"\" vertical-align:=\"\" float:=\"\" clear:=\"\" color:=\"\" font-size:=\"\" background-color:=\"\" width:=\"\"\u003e\u003ca class=\"image-popup\" href=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/mpcc-III-04-gross_826eeb43-7ba8-497d-99a1-b1d430cd7524.jpg?v=1766551485\" target=\"_blank\" style=\"box-sizing: border-box; margin: 0px; padding: 0px; touch-action: manipulation; color: rgb(235, 2, 53); text-decoration: none; transition: all 0.2s;\"\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/mpcc-III-04-gross_826eeb43-7ba8-497d-99a1-b1d430cd7524.jpg?v=1766551485\" alt=\"Koma Korrektor\" title=\"Koma Korrektor\" width=\"250\" style=\"box-sizing: border-box; margin: 0px; padding: 0px; border: none; display: block;\"\u003e\u003c\/a\u003e\u003c\/div\u003e","brand":"Baader Planetarium","offers":[{"title":"Default Title","offer_id":44013368639599,"sku":"MPCC","price":289.99,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/2-mpcc-mark-iii-multi-purpose-coma-corrector-for-newtons-d28__76708.jpg?v=1766551487"},{"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":"sky-watcher-quattro-coma-corrector","title":"Sky-Watcher Quattro Coma Corrector","description":"\u003cspan style=\"font-family: \" open sans sans-serif rgb font-size:=\"\" background-color:=\"\"\u003eDelivers stunning wide-field views with pinpoint stars to the edge of the field. Magnification remains unaltered.\u003c\/span\u003e","brand":"Sky-Watcher","offers":[{"title":"Default Title","offer_id":44013591330927,"sku":"S20204","price":680.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/s20204_quattrocomacorrector_1800x1800__44978.jpg?v=1766557202"},{"product_id":"rcc-i-rowe-coma-corrector","title":"RCC I, Rowe Coma Corrector","description":"\u003cdiv\u003e\u003cspan style=\"font-family: Arial;\"\u003eThe RCC I is designed to correct Coma in fast Newtonian imaging systems. It provides a long back-focus of 91.5 mm measured from the T-2-thread, enabling the use of Off-Axis Guiders, Adaptive Optics and Filter Wheels. Autoguiding can be done easily with the RCC, an RCC Off Axis Guider and an Autoguiding Camera.\u003c\/span\u003e\u003c\/div\u003e\u003cdiv\u003e\u003cspan style=\"font-family: Arial;\"\u003e\u003cbr\u003e\u003c\/span\u003e\u003c\/div\u003e\u003cdiv\u003e\u003cspan style=\"font-family: Arial;\"\u003eThe RCC works from f\/3.5 to f\/6 - it is perfect on f\/4\u003c\/span\u003e\u003c\/div\u003e\u003cdiv\u003e\u003cspan style=\"font-family: Arial;\"\u003ereproduction scale is 1:1 - in contrast to many other coma correctors, the RCC is no Barlow lens which rely on a magnification to make the larger back-focus to the sensor possible\u003c\/span\u003e\u003c\/div\u003e\u003cdiv\u003e\u003cspan style=\"font-family: Arial;\"\u003eThe RCC is the only coma corrector which gives you enough back-focus for filter wheels or other accessories without changing the focal ratio\u003c\/span\u003e\u003c\/div\u003e\u003cdiv\u003e\u003cspan style=\"font-family: Arial;\"\u003e\u003cbr\u003e\u003c\/span\u003e\u003c\/div\u003e\u003cdiv\u003e\u003cspan style=\"font-family: Arial; font-weight: bold;\"\u003eTo attach the RCC directly to a camera (without an Off-Axis-Guider), we recommend the VariLock 46 T-2 Extension (# 2956946, T-2 part-no. #25V). It has got not only a graduated mm-scale, but also a marking at 36.5mm, to show you the perfect working distance for a DSLR with T-2-adapter. Each air\/glass-surface of the triplet RCC optical system is coated with our Phantom Group Coating (R) for the best-possible transmission.\u003c\/span\u003e\u003c\/div\u003e\u003cdiv\u003e\u003cspan style=\"font-family: Arial;\"\u003e\u003cbr\u003e\u003c\/span\u003e\u003c\/div\u003e\u003cdiv\u003e\u003cspan style=\"font-family: Arial;\"\u003eYou can remove the stopper ring to place the RCC deeper inside of your focuser. \u003c\/span\u003e\u003c\/div\u003e","brand":"Baader Planetarium","offers":[{"title":"Baader VariLock 46, Variable Length T-2 Extension tube 29-46mm, with graduated length scale","offer_id":44013657981039,"sku":"RCC-I","price":369.98,"currency_code":"CAD","in_stock":true},{"title":"No Extension","offer_id":44013658013807,"sku":"RCC-I","price":269.99,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/rcc-i-rowe-coma-corrector-03e__01508.jpg?v=1766558913"},{"product_id":"starfield-coma-corrector","title":"Starfield Coma Corrector","description":"\u003cp class=\"MsoNoSpacing\"\u003e\u003cspan style=\"font-size: 12.0pt;\" arial=\"\" sans-serif=\"\" mso-fareast-language:en-ca=\"\"\u003eNewtonian inherit an optical distortion called as Coma, where stars at corner appears not round but bloated like a tadpole shape. The Starfield Optics coma corrector will provide a flat field image when Use on a Newtonian telescope that works from range of F\/3-F\/6. The large 2'' corrector will provide widest field of illumination for even full frame DSLR without vignetting\u003c\/span\u003e\u003c\/p\u003e\n\u003cp class=\"MsoNoSpacing\"\u003e\u003cspan style=\"font-size: 12.0pt;\" arial=\"\" sans-serif=\"\" mso-fareast-language:en-ca=\"\"\u003eThe Starfield Optics 2'' Coma Corrector will significantly enhance your visual experience as well, providing coma free view with sharp pin point stars. \u003c\/span\u003e\u003cspan style=\"font-size: 12.0pt;\" arial=\"\" sans-serif=\"\" mso-fareast-font-family:=\"\" times=\"\" new=\"\" roman=\"\" mso-fareast-language:en-ca=\"\"\u003e2\" nosepiece features recessed safety groove and is threaded to accept standard 2\" filters\u003c\/span\u003e\u003c\/p\u003e\n\u003cul type=\"disc\"\u003e\n\u003cli class=\"MsoNormal\" style=\"mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; line-height: normal; mso-list: l0 level1 lfo1; tab-stops: list 36.0pt; background: white;\"\u003e\n\u003cspan style=\"font-size: 12.0pt;\" arial=\"\" sans-serif=\"\" mso-fareast-font-family:=\"\" times=\"\" new=\"\" roman=\"\" color:black=\"\" mso-color-alt:windowtext=\"\" mso-fareast-language:en-ca=\"\"\u003e2\" eyepiece barrel features brass compression ring and dual large thumbscrews\u003c\/span\u003e\u003cspan style=\"font-size: 12.0pt;\" arial=\"\" sans-serif=\"\" mso-fareast-font-family:=\"\" times=\"\" new=\"\" roman=\"\" mso-fareast-language:en-ca=\"\"\u003e\u003c\/span\u003e\n\u003c\/li\u003e\n\u003cli class=\"MsoNormal\" style=\"mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; line-height: normal; mso-list: l0 level1 lfo1; tab-stops: list 36.0pt; background: white;\"\u003e\u003cspan style=\"font-family: Arial, sans-serif;\"\u003eMagnification\u003cspan style=\"font-size: 12pt;\"\u003e factor of 1.x\u003c\/span\u003e\u003c\/span\u003e\u003c\/li\u003e\n\u003cli class=\"MsoNormal\" style=\"mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; line-height: normal; mso-list: l0 level1 lfo1; tab-stops: list 36.0pt; background: white;\"\u003e\u003cspan style=\"font-size: 12.0pt;\" arial=\"\" sans-serif=\"\" mso-fareast-font-family:=\"\" times=\"\" new=\"\" roman=\"\" color:black=\"\" mso-color-alt:windowtext=\"\" mso-fareast-language:en-ca=\"\"\u003eFully Multicoated\u003c\/span\u003e\u003c\/li\u003e\n\u003cli class=\"MsoNormal\" style=\"mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; line-height: normal; mso-list: l0 level1 lfo1; tab-stops: list 36.0pt; background: white;\"\u003e\n\u003cspan style=\"font-size: 12.0pt;\" arial=\"\" sans-serif=\"\" mso-fareast-font-family:=\"\" times=\"\" new=\"\" roman=\"\" color:black=\"\" mso-color-alt:windowtext=\"\" mso-fareast-language:en-ca=\"\"\u003e3-piece modular design (i) Optics in 2\" nosepiece with 48mm male filter thread (ii) 2' eyepiece barrel that attaches to optical nosepiece, and (iii) M48 - T2 adapter ring\u003c\/span\u003e\u003cspan style=\"font-size: 12.0pt;\" arial=\"\" sans-serif=\"\" mso-fareast-font-family:=\"\" times=\"\" new=\"\" roman=\"\" mso-fareast-language:en-ca=\"\"\u003e\u003c\/span\u003e\n\u003c\/li\u003e\n\u003cli class=\"MsoNormal\" style=\"mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; line-height: normal; mso-list: l0 level1 lfo1; tab-stops: list 36.0pt; background: white;\"\u003e\n\u003cspan style=\"font-size: 12.0pt;\" arial=\"\" sans-serif=\"\" mso-fareast-font-family:=\"\" times=\"\" new=\"\" roman=\"\" color:black=\"\" mso-color-alt:windowtext=\"\" mso-fareast-language:en-ca=\"\"\u003eBack-focus spacing requirement is approx. 70mm +\/- 5mm from the shoulder of the 2\" nosepiece to the image plane\u003c\/span\u003e\u003cspan style=\"font-size: 12.0pt;\" arial=\"\" sans-serif=\"\" mso-fareast-font-family:=\"\" times=\"\" new=\"\" roman=\"\" mso-fareast-language:en-ca=\"\"\u003e\u003c\/span\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp class=\"MsoNormal\" style=\"margin-bottom: 6.75pt; line-height: normal; background: white;\"\u003e\u003cspan style=\"font-size: 12pt; font-family: Arial, sans-serif; color: black; font-weight: bold;\"\u003eFor visual use:\u003c\/span\u003e\u003cspan style=\"font-size: 12.0pt;\" arial=\"\" sans-serif=\"\" mso-fareast-font-family:=\"\" times=\"\" new=\"\" roman=\"\" color:black=\"\" mso-color-alt:windowtext=\"\" mso-fareast-language:en-ca=\"\"\u003e connect the 2\" eyepiece barrel to the main optical nosepiece \u003c\/span\u003e\u003cspan style=\"font-size: 12.0pt;\" arial=\"\" sans-serif=\"\" mso-fareast-font-family:=\"\" times=\"\" new=\"\" roman=\"\" mso-fareast-language:en-ca=\"\"\u003e\u003c\/span\u003e\u003c\/p\u003e\n\u003cp class=\"MsoNormal\" style=\"margin-bottom: 6.75pt; line-height: normal; background: white;\"\u003e\u003cspan style=\"font-size: 12pt; font-family: Arial, sans-serif; color: black; font-weight: bold;\"\u003eFor photo use:\u003c\/span\u003e\u003cspan style=\"font-size: 12.0pt;\" arial=\"\" sans-serif=\"\" mso-fareast-font-family:=\"\" times=\"\" new=\"\" roman=\"\" color:black=\"\" mso-color-alt:windowtext=\"\" mso-fareast-language:en-ca=\"\"\u003e unscrew the 2\" eyepiece barrel and attach the included M48-T2 ring to the main optical nosepiece Then attach your D\/SLR camera to the male T2 thread via a camera-specific T-ring (not included)\u003c\/span\u003e\u003cspan style=\"font-size: 12.0pt;\" arial=\"\" sans-serif=\"\" mso-fareast-font-family:=\"\" times=\"\" new=\"\" roman=\"\" mso-fareast-language:en-ca=\"\"\u003e\u003c\/span\u003e\u003c\/p\u003e\n\u003cp class=\"MsoNormal\" style=\"margin-bottom: 6.75pt; line-height: normal; background: white;\"\u003e \u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e","brand":"Starfield","offers":[{"title":"Default Title","offer_id":44013736820847,"sku":"SF-CM-01","price":160.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/IMG_6600__49086.jpg?v=1766561272"},{"product_id":"starizona-nexus-0-75x-newtonian-focal-reducer-coma-corrector","title":"Starizona Nexus 0.75x Newtonian Focal Reducer\/Coma Corrector","description":"\u003cspan style=\"color: rgb(77, 77, 77); font-family: Lato, sans-serif; font-size: 15px; background-color: rgb(255, 255, 255);\"\u003eNewtonian telescopes require a coma corrector in order to give sharp stars over a large field of view, but most coma correctors keep the telescope's native focal ratio or even make the scope slower. The Nexus instead acts as a coma corrector and also provides a 0.75x focal reduction factor. This turns a common f\/4 Newtonian into an f\/3 system, giving a larger field of view and reducing exposure times by a factor of 1.8x.\u003c\/span\u003e\u003cbr style=\"box-sizing: inherit; -webkit-font-smoothing: antialiased; text-size-adjust: none; -webkit-tap-highlight-color: rgba(0, 0, 0, 0); color: rgb(77, 77, 77); font-family: Lato, sans-serif; font-size: 15px; background-color: rgb(255, 255, 255);\"\u003e\u003cbr style=\"box-sizing: inherit; -webkit-font-smoothing: antialiased; text-size-adjust: none; -webkit-tap-highlight-color: rgba(0, 0, 0, 0); color: rgb(77, 77, 77); font-family: Lato, sans-serif; font-size: 15px; background-color: rgb(255, 255, 255);\"\u003e\u003cspan style=\"color: rgb(77, 77, 77); font-family: Lato, sans-serif; font-size: 15px; background-color: rgb(255, 255, 255);\"\u003eThe Nexus incorporates extra-low dispersion (ED) glass in a sophisticated optical design that gives performance equal to the best coma correctors while decreasing, instead of increasing, the focal length. The Nexus is also designed to be parfocal, so it does not change the original focal point of the telescope. The corrected image circle is 28mm, accommodating camera sensors up to APS format. While nominally designed for the popular commercial f\/4 imaging Newtonians, the Nexus can work with Newtonians as fast at f\/3.\u003c\/span\u003e\u003cbr style=\"box-sizing: inherit; -webkit-font-smoothing: antialiased; text-size-adjust: none; -webkit-tap-highlight-color: rgba(0, 0, 0, 0); color: rgb(77, 77, 77); font-family: Lato, sans-serif; font-size: 15px; background-color: rgb(255, 255, 255);\"\u003e\u003cbr style=\"box-sizing: inherit; -webkit-font-smoothing: antialiased; text-size-adjust: none; -webkit-tap-highlight-color: rgba(0, 0, 0, 0); color: rgb(77, 77, 77); font-family: Lato, sans-serif; font-size: 15px; background-color: rgb(255, 255, 255);\"\u003e\u003cspan style=\"color: rgb(77, 77, 77); font-family: Lato, sans-serif; font-size: 15px; background-color: rgb(255, 255, 255);\"\u003eBackfocus requirement for the Nexus is 55mm, matching the common standard for most coma correctors, field flatteners and focal reducers. This distance allows for the use of DSLRs as well as mirrorless cameras and most astronomical CMOS and CCD cameras. The Nexus has M48 threads on the camera side. The barrel of the Nexus is a standard 2\" diameter to fit most focusers. On the telescope end are M48 threads for a standard 2\" filter.\u003c\/span\u003e","brand":"Starizona","offers":[{"title":"Default Title","offer_id":44013888700527,"sku":"NEXUS-075","price":639.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/NexusFrontView_826x1200_9fd9e8b6-b767-428f-b1a8-6f392825698d_1200x1200__63403.jpg?v=1766565601"},{"product_id":"starizona-sct-corrector-iv-0-63x-reducer-coma-corrector","title":"Starizona SCT Corrector IV - 0.63X Reducer \/ Coma Corrector","description":"\u003cp\u003e\u003cstrong\u003ePerformance\u003c\/strong\u003e\u003c\/p\u003e\n\u003cdiv\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/C11_f6pt3_Spot_Comparison_c86b4ee8-75ce-4333-9fb9-b0a4bb895169.jpg?v=1766566089\" alt=\"\"\u003e\u003c\/div\u003e\n\u003cp\u003eThe diagram above shows how the SCT Corrector improves the off-axis spot size on a Celestron 11\" SCT. Performance is similar on other size telescopes.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eFocal Length\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe exact focal length of the reducer\/telescope combo depends slightly on where in the optical path the SCT Corrector lens is placed. Nominally it will be within a few mm of the rear threads on the telescope. Changing this distance should only affect the focal length, not the optical quality. Listed below are the nominal focal lengths for the various sizes of Celestron SCTs*. The SCT Corrector works great on standard f\/10 Meade SCTs as well, we just didn't have exact data for the nominal designs of those telescopes.\u003c\/p\u003e\n\u003ctable\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd width=\"100\"\u003e\u003cstrong\u003eTelescope\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd width=\"100\"\u003e\u003cstrong\u003eFocal Length\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd width=\"100\"\u003e\u003cstrong\u003eFocal Ratio\u003c\/strong\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eC6\u003c\/td\u003e\n\u003ctd\u003e1220mm\u003c\/td\u003e\n\u003ctd\u003ef\/8\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eC8\u003c\/td\u003e\n\u003ctd\u003e1450mm\u003c\/td\u003e\n\u003ctd\u003ef\/7.1\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eC9.25\u003c\/td\u003e\n\u003ctd\u003e1525mm\u003c\/td\u003e\n\u003ctd\u003ef\/6.5\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eC11\u003c\/td\u003e\n\u003ctd\u003e1760mm\u003c\/td\u003e\n\u003ctd\u003ef\/6.3\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eC14\u003c\/td\u003e\n\u003ctd\u003e2365mm\u003c\/td\u003e\n\u003ctd\u003ef\/6.7\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003cp\u003e\u003cem\u003e* The SCT Corrector has a reduction factor of 0.63x, but the C6 and C8 are actually closer to f\/11 natively, and they have a shorter backfocus compared to the larger scopes so the reduction is a bit less.  The C14 is f\/11 natively.\u003cbr\u003e\u003c\/em\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCamera Adapters\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe SCT Corrector IV has a nominal image circle of 27mm, accommodating most popular CCDs and DSLRs. For larger format cameras, check out our\u003cspan\u003e \u003c\/span\u003e\u003ca href=\"https:\/\/starizona.com\/products\/starizona-sct-corrector-lf-large-format-reducer-coma-corrector\"\u003eSCT Corrector LF.\u003c\/a\u003e\u003c\/p\u003e\n\u003cp\u003eBecause the backfocus of the SCT Corrector IV is fairly critical, for best performance Starizona makes a variety of camera adapters, and custom adapters are also easy to make for less-common camera setups.\u003c\/p\u003e\n\u003cp\u003eThe nominal backfocus is 90.3mm from the base of the threads on the camera side of the SCT Corrector IV. For the largest compatible cameras, this should be kept within +\/-2mm, while smaller format cameras may work fine at slightly larger tolerances. If we do not have the correct length or style adapter you need, we can gladly make the correct part to get the best performance from your setup. Please contact with any questions on making your camera configuration work.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eTelescope Adapters\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe SCT Corrector IV, like the original SCT Corrector, has a 2\" barrel that allows it to fit into a 2\" visual back or 2\" focuser. If your telescope does not have such an adapter, we recommend our\u003cspan\u003e Virtual View\u003c\/span\u003e\u003cspan\u003e \u003c\/span\u003erotating visual back, which allows for easily changing the camera orientation without loosening any lock screws.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eFilters\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe front (telescope side) of the SCT Corrector IV is threaded to accept standard 2\" (48mm) filters.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eFeatures\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e0.63x focal reduction factor\u003c\/li\u003e\n\u003cli\u003e2.5x faster than SCT's native f\/10\u003c\/li\u003e\n\u003cli\u003e1.4x faster than original f\/7.5 SCT Corrector design\u003c\/li\u003e\n\u003cli\u003e27mm image circle\u003c\/li\u003e\n\u003cli\u003e2\" barrel diameter\u003c\/li\u003e\n\u003cli\u003e2.5\" length excluding threads\u003c\/li\u003e\n\u003cli\u003eThreaded for 48mm filters\u003c\/li\u003e\n\u003cli\u003eSCT Corrector Top Thread: M42 x 0.75mm T-thread\u003c\/li\u003e\n\u003cli\u003eMechanical Backfocus (thread shelf to focal plane): 90.3mm (3.56”)\u003c\/li\u003e\n\u003cli\u003eBlack anodized, machined aluminum housing\u003c\/li\u003e\n\u003cli\u003eFully multi-coated optics\u003c\/li\u003e\n\u003cli\u003e5-element optical design with extra-low dispersion (ED) glass\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Starizona","offers":[{"title":"Default Title","offer_id":44013906788463,"sku":"SCTCORR-4","price":564.99,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/sct-1_650x650__17442.jpg?v=1766566091"},{"product_id":"starizona-sct-corrector-lf-large-format-reducer-coma-corrector","title":"Starizona SCT Corrector LF - Large Format Reducer\/Coma Corrector","description":"\u003cp\u003e\u003cspan\u003eStarizona's SCT Corrector has been an incredibly popular focal reducer and coma corrector, giving astrophotographers with standard Schmidt-Cassegrain telescopes an improved optical system and wider field of view, with increased photographic speed. Starizona now offers a large-format version, the SCT Corrector LF, designed to cover full-frame (35mm format) sensors.\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003eThe SCT Corrector LF is designed for Celestron 11\" and 14\" standard SCTs. Designed to thread directly onto the large 3.29\" threads on the rear cell of C11 and C14 telescopes, the larger optical elements of the SCT Corrector LF minimize the vignetting over large sensors. Remaining vignetting over a large field is minimal and limited only by the telescope baffles, which are designed for a slower focal ratio; but this vignetting is easily removed by using flat field images. Sharpness is excellent over a 42mm diagonal, with spots sizes up to 9x smaller than the native telescope! The focal ratio is reduced to f\/7.2 on the C14 and f\/7 on the C11, for a speed increase of 2.1x and 1.9x, respectively.\u003c\/p\u003e\n\u003cp\u003eThe SCT Corrector LF is designed to increase the available backfocus compared to Starizona's standard SCT Corrector. Backfocus is 146, accommodating a variety of accessories. The rear threads on the SCT Corrector LF are the same 3.29\" threads as on the rear cell of the C11 and C14 telescopes, so standard accessories are easily attached.\u003c\/p\u003e\n\u003cdiv\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/SCT_LF_Spots_6d8891ac-8d5b-4f35-a0b5-e5b3b672cf58.jpg?v=1766566119\" alt=\"\"\u003e\u003c\/div\u003e\n\u003cp\u003e\u003cstrong\u003eAbove:\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003e\u003cem\u003eSpots sizes compared for a native C14 at f\/11 versus a C14 at f\/7.5 with the SCT Corrector LF. Each small square in the diagram is 40 microns. The RMS spot size at the edge of the field for the native C14 is 106 microns and the SCT Corrector LF is just 13 microns!\u003c\/em\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eC11 Specifications\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eFocal Ratio:\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003ef\/7\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFocal Length:\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003e1960mm\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cstrong\u003eC14 Specifications\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eFocal Ratio:\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003ef\/7.2\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFocal Length:\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003e2560mm\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cstrong\u003eGeneral Specifications\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eImage Circle:\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003e42mm\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMechanical Backfocus:\u003c\/strong\u003e 146mm from top of mounting threads\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMaximum Diameter:\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003e3.5\"\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOverall Length:\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003e2.7\" (length added from normal mounting threads is 2.3\")\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMounting Thread:\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003eStandard C11\/14 3.29\"-16tpi thread\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWeight:\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003e1.6 lbs (730g)\u003c\/li\u003e\n\u003cli\u003e\u003cstrong\u003eFully AR coated optics\u003c\/strong\u003e\u003c\/li\u003e\n\u003cli\u003e\u003cstrong\u003eMade in USA\u003c\/strong\u003e\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Starizona","offers":[{"title":"Default Title","offer_id":44013907738735,"sku":"SCTCORR-LF","price":709.99,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/sct-lf2_1_650x650__01433.jpg?v=1766566121"},{"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"}],"url":"https:\/\/ontariotelescope.com\/collections\/fr-coma-correctors.oembed","provider":"Ontario Telescope and Accessories","version":"1.0","type":"link"}