{"title":"Explore Scientific Diagonals","description":"\u003cp\u003eExplore Scientific diagonals 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-2-diagonal","title":"Explore Scientific 99% Reflective 2-Inch Dielectric Star Diagonal","description":"\u003ch3\u003e\u003cstrong\u003eProduct Overview\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThe Explore Scientific DD02-00CF is a 2-inch star diagonal with a dielectric-coated first-surface mirror rated at 99% reflectivity. Published dimensions are 104.8 mm long, 60.9 mm wide and 127.0 mm high, at 1.0 lb; 0.45 kg. It ships with a 1.25-inch adapter and dust covers.\u003c\/p\u003e\n\u003cp\u003eA star diagonal turns the light path through 90 degrees so the eyepiece points upward rather than straight back along the tube. On a refractor or a Cassegrain that is the difference between observing comfortably and lying under the telescope to reach the eyepiece at high elevation. The image is presented right way up but reversed left to right, which is normal for a mirror diagonal.\u003c\/p\u003e\n\u003cp\u003eThe mechanical detail here is the insertion system: a double-taper insert barrel at the telescope end and compression ring locks on both eyepiece holders. A compression ring spreads the clamping force around a barrel instead of driving a thumbscrew point into it, so eyepiece and adapter barrels come out unmarked.\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\u003eRefractor owners:\u003c\/strong\u003e a straight-through refractor puts the eyepiece at the low end of the tube, which is where a diagonal earns its place immediately.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCassegrain and SCT owners:\u003c\/strong\u003e the 2-inch fitting is the standard path for these telescopes to reach wide-field eyepieces.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eObservers running mixed eyepiece sets:\u003c\/strong\u003e the supplied 1.25-inch adapter means both barrel sizes work through the same diagonal.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAnyone whose eyepiece barrels have been scarred by set screws:\u003c\/strong\u003e compression rings on both holders exist specifically to stop that.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eObservers who want light throughput preserved:\u003c\/strong\u003e at 99% reflectivity, a dielectric coating gives up substantially less than an aluminised mirror does.\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\u003e99% reflective dielectric coating:\u003c\/strong\u003e dielectric mirrors work by stacking many thin transparent layers whose reflections reinforce one another, rather than by depositing metal. The result is higher reflectivity than aluminium and no metal layer to tarnish over time.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFirst-surface mirror:\u003c\/strong\u003e the coating sits on the front face of the glass, so light never passes through the substrate. That removes the ghost image a second-surface mirror produces.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDouble-taper insert barrel:\u003c\/strong\u003e the taper resists the diagonal being pulled out of a focuser by a loosening thumbscrew.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCompression ring locks on both eyepiece holders:\u003c\/strong\u003e both the 2-inch holder and the 1.25-inch adapter clamp without marking accessory barrels.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e1.25-inch adapter included,\u003c\/strong\u003e so 1.25-inch eyepieces work without a separate purchase.\u003c\/li\u003e\n\u003cli\u003e\u003cstrong\u003eDust covers included.\u003c\/strong\u003e\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePublished dimensions:\u003c\/strong\u003e 104.8 mm long, 60.9 mm wide, 127.0 mm high, 1.0 lb; 0.45 kg.\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\u003eVisual observing through refractors, SCTs and Maksutov-Cassegrains with 2-inch focusers.\u003c\/li\u003e\n\u003cli\u003eWide-field observing with 2-inch eyepieces, which need a 2-inch light path to show their full field.\u003c\/li\u003e\n\u003cli\u003eHigh-elevation and near-zenith observing, where a straight-through view becomes awkward.\u003c\/li\u003e\n\u003cli\u003eOutreach sessions, where a comfortable eyepiece position keeps a queue moving.\u003c\/li\u003e\n\u003cli\u003eMixed 2-inch and 1.25-inch eyepiece sets, using the supplied adapter.\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\u003eFocuser:\u003c\/strong\u003e fits 2-inch focusers and 2-inch visual backs. Telescopes with 1.25-inch focusers need a 1.25-inch diagonal instead, and we stock those.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEyepieces:\u003c\/strong\u003e takes 2-inch eyepieces directly and 1.25-inch eyepieces through the included adapter, both held by compression rings.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFilters:\u003c\/strong\u003e 2-inch threaded filters are normally fitted to the eyepiece or to the diagonal's nosepiece. Explore Scientific does not publish a filter thread specification for this diagonal, so that row is absent from the table below rather than estimated.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eImage orientation:\u003c\/strong\u003e a mirror diagonal gives an upright but left-right reversed image. For terrestrial use where correct orientation matters, an erecting prism is the alternative.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWeight:\u003c\/strong\u003e 1.0 lb; 0.45 kg, plus whatever eyepiece follows it. On a small refractor that combination sits well behind the balance point.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAstrophotography:\u003c\/strong\u003e a diagonal adds length to the light path and a reflection to the optical train. Most imaging is done straight through, with the diagonal removed.\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\u003eExplore Scientific does not publish an optical path length or a clear aperture figure for this diagonal,\u003c\/strong\u003e so those rows are absent below rather than estimated. Path length is the figure that matters when a telescope is close to running out of focuser travel — if you are working out a train, send us the details and we will look at it with you.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIt needs a 2-inch focuser.\u003c\/strong\u003e There is no way to fit a 2-inch diagonal to a 1.25-inch focuser, and a 1.25-inch diagonal is the right part in that case.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eThe view is mirror-reversed left to right.\u003c\/strong\u003e That is inherent to a single-mirror diagonal and is of no consequence for astronomy, where there is no correct orientation. For daytime and terrestrial viewing, an erecting prism gives a fully correct image and we stock those.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAdding a diagonal changes where focus falls.\u003c\/strong\u003e A telescope that focused straight through will need the focuser moved inward once the diagonal is in place, since the diagonal contributes its own path length. Almost every telescope designed for visual use has the range for this built in.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTogether with a heavy 2-inch eyepiece it forms a substantial tail load.\u003c\/strong\u003e At 1.0 lb; 0.45 kg the diagonal is modest, but a 600g eyepiece behind it shifts balance on a light tube — a counterweight or a tube-ring adjustment settles it.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eFrequently Asked Questions\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eIs it difficult to set up?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eNo — the barrel goes into the 2-inch focuser, the eyepiece goes into the diagonal, and the compression rings hold both. Refocusing after fitting it is the only step, and there is nothing to align or adjust.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat does the dielectric coating actually do?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eIt reflects 99% of the light using stacked thin transparent layers rather than a metal film. That means more light reaching the eyepiece than an aluminised mirror delivers, and no metal coating to degrade over the years.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDoes it come with a 1.25-inch adapter?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eYes, along with dust covers, so both eyepiece barrel sizes work straight away.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWill it mark my eyepiece barrels?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eBoth holders use compression ring locks, which press a split ring evenly around the barrel rather than driving a screw into it. That is the design specifically intended to leave barrels unmarked.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCan I use it for photography?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eIt is built for visual observing. Imaging is usually done with the diagonal removed, since a straight path is shorter and has one fewer reflection in it.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhy is the image flipped left to right?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eA single mirror reverses handedness. Every star diagonal of this type does it, and for astronomy it makes no practical difference. If you want a correctly oriented daytime image, an erecting prism is the part to look at and we can suggest one.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eIn short: a 2-inch star diagonal with a 99% reflective dielectric first-surface mirror, a double-taper insert barrel, compression ring locks on both holders, and a 1.25-inch adapter and dust covers in the box, at 1.0 lb; 0.45 kg. If you would like us to check that it suits your focuser and the eyepieces you already own, send us the telescope model and we will look at it with you.\u003c\/p\u003e","brand":"Explore Scientific","offers":[{"title":"Default Title","offer_id":44012982173807,"sku":"DD02-00CF","price":304.95,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/explore-scientific-2-inch-99-reflective-dielectric__34009.jpg?v=1766548370"},{"product_id":"explore-scientific-3-inch-99-dielectric-star-diagonal","title":"Explore Scientific 3-inch 99% Dielectric Star Diagonal with 2-inch Adapter","description":"\u003ch2\u003eProduct Overview\u003c\/h2\u003e\u003cp\u003eThe Explore Scientific 3-inch Dielectric-Coated Diagonal Mirror turns the light path 90 degrees for comfortable viewing on a refractor, and does so with a first-surface coated mirror that reflects 99% of the light reaching it. It ships with a 2-inch adapter and dust covers, and weighs 2.0 lb.\u003c\/p\u003e\u003ch2\u003eWho It's For\u003c\/h2\u003e\u003cp\u003eThis is the diagonal for an observer running a large refractor with a 3-inch focuser who does not want the diagonal to be the narrowest point in the optical path. A 2-inch diagonal on a 3-inch focuser throws away field at the edges; this one passes the full aperture. It suits anyone using wide-field 2-inch eyepieces on a 120 mm or larger refractor.\u003c\/p\u003e\u003ch2\u003eKey Features \u0026amp; Design\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003e99% reflective dielectric coating on a first-surface mirror, preserving image brightness\u003c\/li\u003e\n\u003cli\u003eFull 3-inch clear path with no restriction ahead of the eyepiece\u003c\/li\u003e\n\u003cli\u003eDouble-taper insert barrel for smooth insertion and withdrawal from the focuser\u003c\/li\u003e\n\u003cli\u003eWide section of the taper prevents the diagonal dropping out if the focuser set screw loosens\u003c\/li\u003e\n\u003cli\u003eCompression ring lock on the 2-inch eyepiece holder, gripping without marking the barrel\u003c\/li\u003e\n\u003cli\u003e2-inch adapter and dust covers included\u003c\/li\u003e\n\u003cli\u003eSolid but light construction at 2.0 lb\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch2\u003eOptical and Mechanical Design\u003c\/h2\u003e\u003cp\u003eA first-surface mirror carries its reflective coating on the front of the glass, so light never passes through the substrate — that removes the faint secondary reflection a rear-coated mirror produces around bright objects. The dielectric coating is a multi-layer stack tuned for reflectivity across the visual band rather than a metal film, which is what allows a 99% figure and why it does not tarnish with age. The double-taper barrel is a mechanical safety feature as much as a convenience: a heavy diagonal and eyepiece cannot slide free of a loosened set screw.\u003c\/p\u003e\u003ch2\u003eRecommended Uses\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003eVisual observing with a large refractor at a comfortable eyepiece angle\u003c\/li\u003e\n\u003cli\u003eWide-field views with 2-inch eyepieces where full aperture matters at the field edge\u003c\/li\u003e\n\u003cli\u003eLunar, planetary and double star work where every percent of light and contrast counts\u003c\/li\u003e\n\u003cli\u003eAny 3-inch focuser setup where a 2-inch diagonal would be the limiting aperture\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch2\u003eCompatibility and Accessory Notes\u003c\/h2\u003e\u003cp\u003eThe diagonal is built for a 3-inch focuser such as the Explore Scientific ES-FOC3, and the supplied 2-inch adapter lets you use your existing 2-inch eyepieces straight away. A 1.25-inch eyepiece holder is available separately if you also want to use smaller barrels; it has its own compression ring lock. Both holders secure eyepieces with compression rings rather than a bare set screw, so eyepiece barrels stay unmarked. We stock 2-inch eyepieces across the Explore Scientific 68°, 82° and 92° series if you are building out a set.\u003c\/p\u003e\u003ch2\u003eGood to Know Before You Order\u003c\/h2\u003e\u003cp\u003eThis is a 3-inch diagonal — it needs a 3-inch focuser, and will not fit a 2-inch one. The 1.25-inch eyepiece holder is a separate purchase, so if most of your eyepieces are 1.25-inch it is worth adding. At 2.0 lb plus an eyepiece it is a real load on the focuser, which is part of why it pairs naturally with a heavy-duty 3-inch focuser rated for the weight. Not sure whether your focuser takes it? Send us the model and we will confirm.\u003c\/p\u003e\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\u003cp\u003e\u003cstrong\u003eIs it difficult to set up?\u003c\/strong\u003e No. It slides into a 3-inch focuser and locks with the focuser's own mechanism; the eyepiece drops into the compression ring holder and tightens by hand.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWill my 2-inch eyepieces work?\u003c\/strong\u003e Yes — the 2-inch adapter is included in the box.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat about 1.25-inch eyepieces?\u003c\/strong\u003e A 1.25-inch holder is available separately and adds a second compression ring lock.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhy choose a 3-inch diagonal over a 2-inch?\u003c\/strong\u003e On a 3-inch focuser a 2-inch diagonal becomes the narrowest point in the light path and clips the outer field. A 3-inch diagonal keeps the full aperture through to the eyepiece.\u003c\/p\u003e\u003ch2\u003eBottom Line\u003c\/h2\u003e\u003cp\u003eA 99% dielectric first-surface mirror in a full 3-inch body, with the 2-inch adapter and dust covers included and a barrel designed not to let go. The right diagonal for a large refractor running a 3-inch focuser. Our Bolton team can confirm fit and suggest eyepieces to match.\u003c\/p\u003e","brand":"Explore Scientific","offers":[{"title":"Default Title","offer_id":53956030201967,"sku":"DD03-01CF","price":817.95,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/DD03-01CF_1_55bf8ec6-c7ec-4584-b1a9-a36a2163be15.jpg?v=1785953832"}],"url":"https:\/\/ontariotelescope.com\/collections\/explore-scientific-diagonals.oembed","provider":"Ontario Telescope and Accessories","version":"1.0","type":"link"}