{"title":"Explore Scientific Adapters","description":"\u003cp\u003eExplore Scientific adapters stocked at Ontario Telescope. Goods ship factory-sealed. If you're unsure what fits your setup, ask us before you order and we'll confirm it.\u003c\/p\u003e","products":[{"product_id":"explore-scientific-rack-and-pinion-focuser-2-extension-tube","title":"Explore Scientific ESRPEXT2 1.5-Inch Extension Tube for 2-Inch Rack and Pinion Focusers","description":"\u003ch3\u003e\u003cstrong\u003eProduct Overview\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThis is an Explore Scientific extension tube for the 2-inch rack-and-pinion focusers fitted to their ED APO telescopes, carried under item number ESRPEXT2. It adds 1.5 inches of additional travel to the focuser, which lets an imaging or visual train reach focus in configurations that would otherwise run past the end of the focuser's native range.\u003c\/p\u003e\n\u003cp\u003eIt is a plain machined tube. There is no glass in it, no moving part and no electronics — it sits between the focuser and whatever follows it, and its only job is to place that equipment 1.5 inches further back.\u003c\/p\u003e\n\u003cp\u003eEvery telescope brings light to focus a fixed distance behind the focuser flange. A visual eyepiece in a diagonal usually lands inside the focuser's travel comfortably; a camera, a binoviewer, a filter wheel or a long adapter stack often does not, and the focuser reaches the end of its outward travel before the image is sharp. An extension tube moves the whole train outward by a known amount so that focus falls back inside the range the focuser actually has.\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 Explore Scientific ED APO telescopes with 2-inch rack-and-pinion focusers,\u003c\/strong\u003e which is the fitment this tube is specified for.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAnyone whose focuser runs out of outward travel\u003c\/strong\u003e before an image comes to focus — the classic symptom being a focuser racked fully out with the stars still soft.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBinoviewer users:\u003c\/strong\u003e a binoviewer consumes a large amount of light path, and reaching focus with one is a common reason to add a fixed extension.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eImagers assembling a train:\u003c\/strong\u003e when the sum of camera, filter wheel, spacers and adapter comes up short of the required distance, a fixed extension is the simplest way to make up the difference.\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\u003eAdds 1.5 inches of travel\u003c\/strong\u003e to the focuser's native range.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMade for 2-inch rack-and-pinion focusers\u003c\/strong\u003e on Explore Scientific ED APO telescopes.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMachined tube with no optical elements:\u003c\/strong\u003e nothing in the light path to add aberration, reflection or colour.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNo moving parts:\u003c\/strong\u003e a fixed spacer holds its length exactly, which is what makes it predictable in an imaging train where spacing is arithmetic.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eItem number ESRPEXT2,\u003c\/strong\u003e the designation to quote when checking fitment against a particular telescope.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSupplied on its own\u003c\/strong\u003e — the vendor lists no additional included accessories with it.\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\u003eReaching focus with a binoviewer, which typically needs more light path than a single eyepiece.\u003c\/li\u003e\n\u003cli\u003eAdding length to an imaging train that falls short of the required backfocus distance.\u003c\/li\u003e\n\u003cli\u003eRestoring focus after a diagonal has been removed from a visual setup, which shortens the path considerably.\u003c\/li\u003e\n\u003cli\u003eGiving a camera enough standoff from the focuser that the focuser is not working at the very end of its travel, where a rack-and-pinion is least well supported.\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\u003eFitment:\u003c\/strong\u003e specified for the 2-inch rack-and-pinion focusers used on Explore Scientific ED APO telescopes. If you are unsure which focuser your tube carries, send us the model and we will check it.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLength added:\u003c\/strong\u003e 1.5 inches, which is 38.1mm. That is the figure to use when adding up an imaging train.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDirection of the change:\u003c\/strong\u003e an extension pushes the focus point outward. Where a setup already reaches focus with the drawtube well in, adding this tube pushes it further out and may take some setups past their inward range instead — which is why extensions are added to trains that come up short rather than as a default.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOptical effect:\u003c\/strong\u003e none of its own. There is no glass, so it changes distance and nothing else.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFilters:\u003c\/strong\u003e the vendor does not publish a filter thread for this tube, so that row is absent from the specifications rather than estimated.\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\u003eThe vendor lists this item under two names.\u003c\/strong\u003e Explore Scientific titles it a 1.5-inch extension tube while the part is catalogued as the 2-inch rack-and-pinion focuser extension — the 2 inches refers to the focuser it fits and the 1.5 inches to the travel it adds. Item number ESRPEXT2 identifies it either way.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eExplore Scientific publishes no dimensional or weight specification for this part.\u003c\/strong\u003e Outer diameter, thread type, material and mass are not given, so those rows are absent below rather than estimated. If a specific figure decides the purchase for you, ask us and we will put the question to our Explore Scientific rep.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAn extension solves a shortfall, not a surplus.\u003c\/strong\u003e Where a train already focuses with room to spare, adding length works against you. The useful check is whether the focuser currently runs out of outward travel before the image sharpens.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAny extension adds a joint to the light path.\u003c\/strong\u003e With a heavy camera on the end, that additional cantilever is worth accounting for in how the train is supported — keeping the heaviest item as close to the focuser as the spacing allows is the usual approach.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFitment is worth checking once rather than guessing.\u003c\/strong\u003e Send us your telescope model and the accessories going behind it and we will tell you whether this is the right part before it ships.\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 threads or slots into the 2-inch rack-and-pinion focuser and the eyepiece, diagonal or camera goes on after it. There is nothing to adjust, align or calibrate, and refocusing after fitting it is the only step.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eHow much length does it add?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003e1.5 inches, which is 38.1mm.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWill it degrade the image?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThere is no glass in it, so it introduces no aberration of its own. What it changes is the distance between the focuser and everything behind it.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eHow do I know whether I need one?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe usual sign is a focuser racked all the way out with the image still soft — the focus point is falling behind where the drawtube can reach. Send us a list of what is in your train and we will work out whether 1.5 inches is the right amount.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDoes it work with a binoviewer?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eBinoviewers are one of the common reasons to add a fixed extension, because they consume a substantial amount of light path. Whether 1.5 inches is enough depends on the particular binoviewer, so send us the model and we will check.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWill it fit a focuser from another brand?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eIt is specified for Explore Scientific 2-inch rack-and-pinion focusers. Other 2-inch focusers vary in how they accept accessories, so tell us what you have and we will look at 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 simple machined extension that adds 1.5 inches of travel to the 2-inch rack-and-pinion focusers on Explore Scientific ED APO telescopes, with no glass and nothing to adjust — the straightforward fix when a camera, binoviewer or adapter stack pushes focus beyond the focuser's reach. Send us your telescope and the accessories behind it and we will tell you whether this is the piece that closes the gap.\u003c\/p\u003e","brand":"Explore Scientific","offers":[{"title":"Default Title","offer_id":44013540311151,"sku":"ESRPEXT2","price":54.95,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/ESRPEXT2_Bottom_1800x1800__39608.jpg?v=1766555687"},{"product_id":"explore-scientific-50mm-2-inch-t2-camera-adapter","title":"Explore Scientific 50mm 2-inch Camera Adapter with T2 Thread for DSLR Prime Focus Imaging","description":"\u003ch2\u003eProduct Overview\u003c\/h2\u003e\u003cp\u003eThe Explore Scientific 50mm (2-inch) T2 Camera Adapter is the piece that bridges a 2-inch focuser and a camera-specific T-ring. The telescope side is a 2-inch fitting that goes into any 2-inch or larger focuser or star diagonal. The camera side carries a male T2 thread, which is the M42 x 0.75 standard that Canon, Nikon, Sony, Pentax and every other mainstream T-ring is cut to accept. Explore Scientific publishes an outside diameter of 76 mm, a height of 36 mm, and a weight of 0.15 lb (0.08 kg), and describes it as suiting any telescope with a 2-inch or larger focuser. Vendor item number 510365.\u003c\/p\u003e\u003ch2\u003eWho It's For\u003c\/h2\u003e\u003cp\u003eThis is for the imager who wants the telescope to be the lens. In prime focus astrophotography you take the camera lens off entirely and let the objective project directly onto the sensor, and to do that you need an unbroken mechanical chain from the drawtube to the camera body. Your T-ring handles the camera end and terminates in a female T2 thread. Something has to present a male T2 thread at the telescope end, and that is exactly what this adapter is for. Without it you are left holding a T-ring with nothing to screw it onto.\u003c\/p\u003e\u003cp\u003eIt also earns its place if you move one camera between several scopes. Because the telescope side is a plain 2-inch fitting and the camera side is the universal T2 standard, one adapter serves every 2-inch focuser you own, and changing camera systems means buying a new T-ring rather than a new adapter. For visual observers who occasionally shoot the Moon or a bright planet with a DSLR, it is the cheapest way to make that possible without rebuilding the imaging train.\u003c\/p\u003e\u003ch2\u003eKey Features \u0026amp; Design\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003eMale T2 thread (M42 x 0.75) on the camera side, matching the T-mount standard used by mainstream DSLR and mirrorless T-rings\u003c\/li\u003e\n\u003cli\u003e2-inch telescope side, so it works with any 2-inch or larger focuser or star diagonal\u003c\/li\u003e\n\u003cli\u003e76 mm published outside diameter and 36 mm published height, so you can budget its contribution to the optical path before you order\u003c\/li\u003e\n\u003cli\u003ePublished weight of 0.15 lb (0.08 kg), light enough that it changes nothing about focuser balance or drawtube sag\u003c\/li\u003e\n\u003cli\u003eCamera-agnostic by design: change bodies or brands and you only replace the T-ring, not this adapter\u003c\/li\u003e\n\u003cli\u003eThreaded camera interface rather than a compression ring, so once the T-ring is snug the camera cannot rotate or creep during a long exposure\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch2\u003eMechanical Design\u003c\/h2\u003e\u003cp\u003eThe whole point of this part is thread standards, so it is worth being precise. T2, sometimes written T-mount, is a 42 mm diameter male thread with a 0.75 mm pitch — M42 x 0.75. It is not the same as the old M42 x 1.0 Pentax screw mount, and the two will cross-thread if you force them, so check the pitch rather than the diameter. The T2 standard also carries a spacing convention: a T-ring is machined so that the sensor sits roughly 55 mm behind the shoulder of the male T2 thread. That figure exists because camera flange distances differ — a Canon EOS body registers at about 44 mm and a Nikon F body at about 46.5 mm — and the T-ring makes up the remainder so that every system arrives at the same 55 mm. It matters here because the adapter's 36 mm height is 36 mm of focuser in-travel you have to give back. A refractor with a generous drawtube will not notice; a Newtonian with the focuser board set for eyepieces may not reach focus at all without moving the primary or adding a low-profile focuser. Work out your available in-travel before you order rather than after.\u003c\/p\u003e\u003ch2\u003eRecommended Uses\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003ePrime focus DSLR or mirrorless imaging of the Moon, the Sun with proper full-aperture filtration, and bright planets\u003c\/li\u003e\n\u003cli\u003eDeep-sky imaging with a crop-sensor body where the M42 clear aperture is not a limitation\u003c\/li\u003e\n\u003cli\u003eAttaching a camera to a 2-inch focuser on a scope that has no dedicated rear thread of its own\u003c\/li\u003e\n\u003cli\u003eSharing one camera across several telescopes without buying an adapter for each\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch2\u003eCompatibility and Accessory Notes\u003c\/h2\u003e\u003cp\u003eYou need a T-ring for your specific camera mount, and it must be a T2 ring — female M42 x 0.75. This is the point where imagers most often order the wrong part, so read carefully: Explore Scientific's own Canon EOS and Nikon camera rings in this range are M48 x 0.75, not M42, and they will not thread directly onto this adapter. Those larger rings belong on an M48 imaging train. Explore Scientific's M48 to M42 reduction adapter is the part that normally bridges the two standards, but Explore Scientific does not publish which end of that ring is male and which is female, and a ring sold as an M48-to-M42 reduction and one sold as an M42-to-M48 step-up can be the same object described from opposite ends. Rather than guess, tell us what is on each of your two fittings and we will confirm the bridging part before you order. If your camera ring already says T2, T-mount or M42 x 0.75, none of that applies and this adapter is the correct partner on its own. On the telescope side, any 2-inch focuser or 2-inch star diagonal will accept it, though putting a camera behind a diagonal adds glass and a right-angle bend that most imagers avoid. Fit is genuinely model-dependent once you factor in drawtube depth and available in-travel, so tell our team in Bolton what scope and camera you are pairing and we will confirm the combination before you buy.\u003c\/p\u003e\u003ch2\u003eGood to Know Before You Order\u003c\/h2\u003e\u003cp\u003eThe T-ring is not included and neither is the camera; this adapter is only the middle link. The more important caveat is aperture. An M42 throat gives you somewhere around 38 to 39 mm of clear aperture once the threads are cut, and a full-frame sensor has a 43.3 mm diagonal, so a full-frame body behind any T2 adapter will show darkened corners on a well-illuminated field. That is a property of the T2 standard rather than a fault in this part, and it is precisely why the M48 x 0.75 standard exists. With an APS-C or Micro Four Thirds sensor it is a non-issue. Explore Scientific does not publish a filter thread for this adapter, so if you intend to thread a 2-inch filter into the telescope end, contact us and we will confirm before you order. Finally, remember that 36 mm of mechanical length has to fit inside your focuser's travel range.\u003c\/p\u003e\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\u003cp\u003e\u003cstrong\u003eDoes this include the T-ring for my camera?\u003c\/strong\u003e No. This adapter provides the male T2 thread on the telescope side only. You buy the T-ring separately to match your camera mount, and it screws onto this.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eIs T2 the same as M42?\u003c\/strong\u003e Only partly. T2 is M42 x 0.75, a 42 mm thread with a fine 0.75 mm pitch. The older M42 x 1.0 Pentax screw mount is the same diameter with a coarser pitch and will not mate correctly. Always confirm the pitch.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWill Explore Scientific's M48 Canon or Nikon camera rings screw onto this?\u003c\/strong\u003e Not directly. Those rings are M48 x 0.75 and this adapter presents M42 x 0.75, so a bridging ring between the two standards is required. Because the vendor does not publish thread genders, send us the details of both fittings and we will confirm which ring you need.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWill it vignette my full-frame camera?\u003c\/strong\u003e Very likely at the corners, because the M42 clear aperture is smaller than a full-frame sensor diagonal. Crop-sensor bodies are unaffected. If full-frame coverage matters to you, build the train around M48 components instead.\u003c\/p\u003e\u003ch2\u003eBottom Line\u003c\/h2\u003e\u003cp\u003eThis is a small, inexpensive, well-defined part that does one job properly: it puts a standard male T2 thread on the back of a 2-inch focuser so a T-ring and camera can go on. Match it with a T2 camera ring rather than an M48 one, allow for its 36 mm of length in your focus travel, and it will simply work. If you are unsure which standard your imaging train is built on, contact our team in Bolton and we will sort it out with you before you order.\u003c\/p\u003e","brand":"Explore Scientific","offers":[{"title":"Default Title","offer_id":53958567755887,"sku":"510365","price":96.95,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/1_0a5b31c5-5daf-43bb-a93f-608492ce34d5.jpg?v=1785960535"},{"product_id":"explore-scientific-half-inch-extension-tube-2-inch-rack-and-pinion-focuser","title":"Explore Scientific Half-Inch Extension Tube for 2-inch Rack and Pinion Focusers","description":"\u003ch2\u003eProduct Overview\u003c\/h2\u003e\n\u003cp\u003eThis is Explore Scientific's extension tube for their 2-inch rack and pinion focusers, catalogued as item ESRPEXT1. Explore Scientific describe it in a single line on their own product page: it adds half an inch to the 2-inch rack and pinion focusers fitted to their ED APO telescopes. It is a short, fixed-length spacer that sits in the focuser's optical train and moves the focal plane outwards, and it is the standard remedy when an accessory stack cannot quite reach focus on one of those refractors.\u003c\/p\u003e\n\n\u003ch2\u003eWho It's For\u003c\/h2\u003e\n\u003cp\u003eEvery telescope has a fixed amount of back focus, and every accessory you put behind the focuser spends some of it. A star diagonal, a camera with a long flange distance, a filter wheel, an off-axis guider, a binoviewer, or a field flattener each add optical path, and at some point you run the focuser all the way in and the star image is still not sharp. The opposite problem happens too: you rack the drawtube almost fully out to reach focus, which is exactly where a rack and pinion focuser is least rigid and most prone to sag with a heavy camera hanging off it.\u003c\/p\u003e\n\u003cp\u003eA short extension tube solves both. Adding half an inch of fixed spacing shifts the whole focus range outwards so the drawtube can sit closer to the middle of its travel, where it is well supported and the pinion has good engagement. That is a small change on paper and a large one at the eyepiece: better mechanical stiffness, less differential flexure across a long exposure sequence, and a focuser that is not fighting its own end stops. If you have ever found that a particular diagonal and eyepiece combination will not come to focus on your ED APO while a shorter one will, this is the part you were missing.\u003c\/p\u003e\n\n\u003ch2\u003eKey Features \u0026amp; Design\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003eAdds half an inch of fixed spacing to the optical train, per Explore Scientific's published description.\u003c\/li\u003e\n\u003cli\u003eDesigned by Explore Scientific specifically for their own 2-inch rack and pinion focusers.\u003c\/li\u003e\n\u003cli\u003eIntended for the ED APO refractor range that ships with those focusers.\u003c\/li\u003e\n\u003cli\u003eFixed length, with no moving parts, threads to work loose, or clamping mechanism to introduce slop.\u003c\/li\u003e\n\u003cli\u003eShort enough to shift the focus range without meaningfully increasing the cantilevered load on the drawtube.\u003c\/li\u003e\n\u003cli\u003eExplore Scientific item number ESRPEXT1.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eMechanical Design\u003c\/h2\u003e\n\u003cp\u003eAn extension tube does nothing optically. It has no glass in it and it does not change focal length, focal ratio, or image scale. What it changes is geometry. The focal plane of a refractor sits a fixed distance behind the objective, and the focuser's job is to place your eyepiece or sensor at that plane. The drawtube can only travel so far in each direction, so the set of accessory stacks that can reach focus is bounded at both ends. Inserting a rigid half-inch spacer between the focuser and the accessory adds a constant to the optical path, which translates the entire usable focus window outwards by that same half inch. Anything that previously needed the drawtube racked further in than it could go now falls inside the range. The trade-off is symmetric and worth knowing: the same half inch comes off the other end, so a short-path accessory that used to focus with the drawtube nearly fully out may no longer reach focus with the extension fitted. This is why extensions are treated as a per-configuration part rather than something you leave in permanently.\u003c\/p\u003e\n\n\u003ch2\u003eRecommended Uses\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003eRecovering focus with a long-path accessory stack such as a binoviewer, filter wheel, or off-axis guider.\u003c\/li\u003e\n\u003cli\u003eMoving the drawtube back towards the middle of its travel for better rigidity under an imaging load.\u003c\/li\u003e\n\u003cli\u003eFine-tuning spacing when a diagonal and eyepiece combination will not quite come to focus.\u003c\/li\u003e\n\u003cli\u003eBuilding out a repeatable imaging train where a fixed spacer is preferable to a variable one.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eCompatibility and Accessory Notes\u003c\/h2\u003e\n\u003cp\u003eExplore Scientific state that this extension is for their 2-inch rack and pinion focusers on their ED APO telescopes. They do not publish a list of specific telescope or focuser model numbers on the product page, nor do they publish the fitting's thread or barrel dimensions, so we cannot promise a fit on a third-party focuser or on an Explore Scientific focuser of a different type such as their dual-speed Crayford units. If you tell our team in Bolton which telescope and which focuser you have, we will confirm compatibility with you before it ships rather than have you guess. It is also worth working out how much extra spacing you actually need first, because extensions are only useful in the right length and stacking two short ones is rarely as rigid as fitting one of the correct size.\u003c\/p\u003e\n\n\u003ch2\u003eGood to Know Before You Order\u003c\/h2\u003e\n\u003cp\u003eOne point of honesty about the naming. This item is listed in some catalogues, including the vendor price sheet we work from, as a 1-inch extension tube, but Explore Scientific's own live product page for item ESRPEXT1 describes it as adding half an inch and titles it as a half-inch extension. We have written this listing to the figure the manufacturer currently publishes. If the exact optical length is critical to your imaging train, contact us before ordering and we will measure the part in hand and confirm it for you. Beyond that, this is the extension tube alone with no adapters, compression rings, or spacers included, and it is a spacer rather than a focuser upgrade, so it will not add travel or improve the feel of an existing focuser. 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\n\n\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003eWill this let my camera reach focus?\u003c\/strong\u003e It will if the reason you cannot focus is that your accessory stack is too short and the drawtube is already racked fully out, or if you need to shift the focus window outwards. If you are running out of inward travel instead, an extension makes the problem worse rather than better. Tell us your imaging train and we will work out which direction you need to go.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDoes it fit a Crayford or a third-party focuser?\u003c\/strong\u003e Explore Scientific specify it for their own 2-inch rack and pinion focusers only, and they do not publish the fitting dimensions, so we cannot confirm a fit on anything else. Ask us with your focuser model and we will check.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWill it degrade the image?\u003c\/strong\u003e No. There is no glass in an extension tube, so it introduces no aberration of its own. The only optical consideration is that it changes where the focal plane sits relative to your focuser travel.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCan I stack two of them?\u003c\/strong\u003e Mechanically you can, but each additional joint is another place for tilt and flexure to creep in, which matters for imaging. If you need more than half an inch, we would rather find you a single spacer of the right length.\u003c\/p\u003e\n\n\u003ch2\u003eBottom Line\u003c\/h2\u003e\n\u003cp\u003eA half-inch spacer is a small part that quietly fixes a frustrating problem, letting a stubborn accessory stack come to focus and keeping the drawtube in the stiffer part of its travel. Explore Scientific publish very little about it beyond its purpose, so if the exact length or the fit on your particular focuser matters, contact us and we will confirm both before you order.\u003c\/p\u003e","brand":"Explore Scientific","offers":[{"title":"Default Title","offer_id":53958600720495,"sku":"ESRPEXT1","price":41.95,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/ESRPEXT1_Side.jpg?v=1785960632"},{"product_id":"explore-scientific-t2-reduction-adapter-m48-to-m42","title":"Explore Scientific T2 Reduction Adapter M48 x 0.75 to M42 x 0.75 Thread","description":"\u003ch2\u003eProduct Overview\u003c\/h2\u003e\u003cp\u003eThis is the small ring that lets the two competing astrophotography thread standards talk to each other. Explore Scientific describes it as adapting from the larger M48 x 0.75 thread down to the smaller M42 x 0.75 thread — M42 x 0.75 being the thread the industry calls T2 or T-mount. The published figures are a free inner diameter of 39.0 mm, an outer diameter of 50.65 mm (2 inches), matte black anodised aluminium construction, and a weight of just 10 grams. Explore Scientific singles out one use in particular: fitting 2-inch colour and nebula filters between the camera and the telescope. Vendor item number 510382 \/ 05-10382.\u003c\/p\u003e\u003ch2\u003eWho It's For\u003c\/h2\u003e\u003cp\u003eAstrophotography quietly runs on two thread standards, and sooner or later you own parts from both. T2 (M42 x 0.75) is the older and more universal of the two, and it is what most T-rings, most Barlows with removable heads and most small camera adapters are cut to. M48 x 0.75 is the wider standard that arrived with full-frame sensors, and it is what Explore Scientific's field flatteners, focal reducers and larger camera rings use. When the piece in your hand ends in one and the piece it needs to meet ends in the other, the night stops until you have a ring like this.\u003c\/p\u003e\u003cp\u003eThe other reason to own one is filters. Two-inch astrophotography filters are cut with an M48 x 0.75 thread, which means an M48 junction in the imaging train is also a filter holder. Putting a light pollution or narrowband filter in the train ahead of the camera rather than in front of an eyepiece is often the tidiest place for it, and this adapter creates exactly that junction while stepping the train down to the T2 fittings on the camera side. It is a cheap part that unblocks an expensive one.\u003c\/p\u003e\u003ch2\u003eKey Features \u0026amp; Design\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003eBridges the M48 x 0.75 and M42 x 0.75 (T2) standards in a single ring, so no stack of step rings is needed\u003c\/li\u003e\n\u003cli\u003ePublished free inner diameter of 39.0 mm, which is the true clear aperture of the finished junction\u003c\/li\u003e\n\u003cli\u003ePublished outer diameter of 50.65 mm, the standard 2-inch dimension\u003c\/li\u003e\n\u003cli\u003eAccepts 2-inch colour and nebula filters at the M48 end, per Explore Scientific's own guidance\u003c\/li\u003e\n\u003cli\u003eMachined from aluminium with a matte black anodised finish to keep internal reflections down\u003c\/li\u003e\n\u003cli\u003ePublished weight of 10 grams, which is as close to nothing as a mechanical part gets\u003c\/li\u003e\n\u003cli\u003eAll-threaded connection, so nothing can slip, rotate or sag once tightened\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch2\u003eMechanical Design\u003c\/h2\u003e\u003cp\u003eThe interesting engineering here is what happens to the light path. M48 x 0.75 exists because M42 x 0.75 does not have the aperture to feed a full-frame sensor: a T2 thread leaves roughly 38 to 39 mm of clear opening, and a full-frame sensor has a 43.3 mm diagonal, so the corners get clipped. This adapter's published free inner diameter is 39.0 mm, which tells you plainly what the reduction costs. The moment you step down to T2, the wide M48 aperture upstream stops helping, because the narrowest point in an optical train is the point that governs illumination. That is not a flaw in this ring — 39.0 mm is about as generous as an M42 x 0.75 junction can physically be — but it is the reason this is a compatibility part rather than an upgrade part. If your sensor is APS-C or smaller, its diagonal is around 28 mm and the 39.0 mm opening is irrelevant to your images. If your sensor is full frame, you should be looking for a way to keep the train at M48 all the way to the camera rather than reducing to T2 partway along. The other design consequence is spacing: every ring you insert adds mechanical length, and back focus in a corrected imaging train is usually specified to within a millimetre, so this ring's contribution has to be counted.\u003c\/p\u003e\u003ch2\u003eRecommended Uses\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003eJoining an M48 corrector, flattener or reducer to a T2 camera adapter or T-ring\u003c\/li\u003e\n\u003cli\u003eAdding a 2-inch colour, light pollution or narrowband filter into the imaging train ahead of the camera\u003c\/li\u003e\n\u003cli\u003eMaking an existing T2 accessory usable on a newer M48 telescope-side fitting\u003c\/li\u003e\n\u003cli\u003eCrop-sensor imaging where the 39.0 mm clear aperture is comfortably larger than the sensor diagonal\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch2\u003eCompatibility and Accessory Notes\u003c\/h2\u003e\u003cp\u003eDo not order this on the strength of the name alone — order it on the strength of what is on each of your two parts. Explore Scientific publishes the two thread sizes and the fact that the adapter reduces from M48 to M42, but the page does not state which end is male (external) and which is female (internal), and that detail decides whether it solves your problem or sits in a drawer. Names in this corner of the hobby are not reliable either: a ring described as an M48-to-M42 reduction and a ring described as an M42-to-M48 step-up can be the very same part seen from opposite ends. The way to get this right is to describe both fittings you are trying to join — which threads, and whether each is male or female — and let us match them. This is exactly the sort of thing our team in Bolton will confirm for you before you buy, and it takes one message. Note also that this ring is a different item from the M48 x 0.75 adapter made specifically for the Explore Scientific 0.7x focal reducer and field corrector; that one is a dedicated fitting for a particular corrector, whereas this one is a general-purpose thread reduction.\u003c\/p\u003e\u003ch2\u003eGood to Know Before You Order\u003c\/h2\u003e\u003cp\u003eNo filters, no camera and no other adapters are included; this is the ring on its own. Explore Scientific does not publish a light path length or mechanical thickness for it, which matters because a corrected imaging train usually has a back focus target measured to the millimetre. If you are working to a specific back focus figure, contact us and we will measure the ring on our own scales and callipers before you commit. Be clear-eyed about the aperture too: stepping down to a 39.0 mm opening means a full-frame sensor will show corner falloff regardless of how wide the rest of the train is, so treat this as the part that makes two standards meet rather than the part that improves your images. And because thread gender is not published, please confirm the direction with us if you are ordering to solve a specific fitting problem.\u003c\/p\u003e\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\u003cp\u003e\u003cstrong\u003eIs M42 x 0.75 the same as T2?\u003c\/strong\u003e Yes. T2 and T-mount both refer to a 42 mm thread with a 0.75 mm pitch. It is not the same as the older M42 x 1.0 Pentax screw mount, which shares the diameter but has a coarser pitch and will cross-thread.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eCan I put a 2-inch filter in it?\u003c\/strong\u003e Yes, that is one of the uses Explore Scientific highlights. Two-inch astrophotography filters are threaded M48 x 0.75, so the M48 side of this adapter doubles as a filter cell.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWill it vignette my full-frame camera?\u003c\/strong\u003e The 39.0 mm free inner diameter is smaller than a full-frame sensor's 43.3 mm diagonal, so yes, expect corner falloff. Crop-sensor cameras are unaffected. For full-frame work, keep the train at M48 rather than reducing to T2.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhich end is male and which is female?\u003c\/strong\u003e Explore Scientific does not publish that, and we would rather check than guess. Tell us the two fittings you are joining and we will confirm the correct part before you order.\u003c\/p\u003e\u003ch2\u003eBottom Line\u003c\/h2\u003e\u003cp\u003eTen grams of anodised aluminium that keeps a night from being wasted, provided it is the right ten grams. It joins the M48 and T2 standards and gives you somewhere to put a 2-inch filter, at the cost of a 39.0 mm clear aperture that full-frame sensors will notice. Describe both of your fittings to our team in Bolton and we will confirm this is the ring you need.\u003c\/p\u003e","brand":"Explore Scientific","offers":[{"title":"Default Title","offer_id":53958674481263,"sku":"510382","price":41.95,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/eae563d4684ff310f33a1b54e1795434_0510382_m_1.jpg?v=1785960809"}],"url":"https:\/\/ontariotelescope.com\/collections\/explore-scientific-adapters.oembed","provider":"Ontario Telescope and Accessories","version":"1.0","type":"link"}