{"product_id":"zwo-d25-ar-protective-window","title":"ZWO D25 AR Protective Window","description":"\u003ch3\u003e\u003cstrong\u003eProduct Overview\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThe \u003cstrong\u003eZWO D25 AR Protective Window\u003c\/strong\u003e is a \u003cstrong\u003e25 mm\u003c\/strong\u003e replacement window for ZWO ASI cameras. It is \u003cstrong\u003e1.1 mm\u003c\/strong\u003e thick, figured to \u003cstrong\u003e1\/4 λ flatness\u003c\/strong\u003e, and carries an \u003cstrong\u003eanti-reflective coating\u003c\/strong\u003e. It sits directly in front of the sensor and seals the sensor chamber against dust and humidity.\u003c\/p\u003e\n\u003cp\u003eAn AR window is optically clear. It reduces surface reflections but does \u003cstrong\u003enot\u003c\/strong\u003e block ultraviolet or infrared — that distinction drives most of the buying decision here, and it is covered below.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eWho It's For\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThis is a good match if you own an \u003cstrong\u003eASI174-series camera\u003c\/strong\u003e or an \u003cstrong\u003eASI485MC\u003c\/strong\u003e — both ship with the D25 AR window — and need to replace one that is scratched, fogged, or contaminated beyond cleaning.\u003c\/p\u003e\n\u003cp\u003eIt is also the right choice if you \u003cstrong\u003efilter in the imaging train\u003c\/strong\u003e rather than at the sensor, or if you do \u003cstrong\u003einfrared work\u003c\/strong\u003e that an IR-cut window would defeat outright.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eKey Features \u0026amp; Design\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e25 mm diameter, 1.1 mm thick:\u003c\/strong\u003e the D25 form factor used on ASI174-series and ASI485MC bodies\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAnti-reflective coating:\u003c\/strong\u003e reduces reflection losses and internal glare at the window surfaces, a common origin of halos around bright stars\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOptically clear:\u003c\/strong\u003e passes UV and IR straight through — all wavelength control happens elsewhere\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e1\/4 λ flatness:\u003c\/strong\u003e the window sits in a converging beam directly ahead of the sensor, so surface figure directly affects star shapes\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDust and humidity seal:\u003c\/strong\u003e the window is the sensor chamber's only physical barrier\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\u003e\n\u003cstrong\u003eReplacing a scratched or contaminated AR window\u003c\/strong\u003e on an ASI174-series camera or ASI485MC\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eInfrared and methane-band planetary imaging\u003c\/strong\u003e, which requires infrared to reach the sensor\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMonochrome imaging\u003c\/strong\u003e where a filter wheel already handles wavelength selection\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNarrowband and photometric work\u003c\/strong\u003e, where you want no unnecessary coating shaping the passband\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHigh-frame-rate solar and lunar work\u003c\/strong\u003e with the ASI174, where the sensor's speed is the point and filtering is external\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\u003eMatch models:\u003c\/strong\u003e the ASI174 series. The ASI485MC also ships with this window\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWant IR-cut instead?\u003c\/strong\u003e Fit the D25 UV IR-Cut window — same diameter and thickness, different coating. ZWO names it specifically as the ASI485MC's IR-cut conversion\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDiameter is not interchangeable:\u003c\/strong\u003e D25 fits 25 mm bodies only. Smaller planetary bodies take the D21; ASI1600 \/ ASI294 \/ ASI183 \/ ASI533 take the D32; ASI6200 \/ ASI2400 \/ ASI2600 take the D60\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNo installation direction:\u003c\/strong\u003e ZWO confirms the window has no preferred orientation, so the coating works either way round\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eReplacement procedure:\u003c\/strong\u003e see ZWO's official guide, \u003ca href=\"https:\/\/i.zwoastro.com\/wp-content\/uploads\/2025\/12\/c36da643469647ac8334179b49aa8b11.pdf\" target=\"_blank\" rel=\"noopener\"\u003eHow to Replace the Camera Protective Window\u003c\/a\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMechanical part only\u003c\/strong\u003e — no electronic function, no camera communication\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eImportant Limitations\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eThis window does not cut UV or IR.\u003c\/strong\u003e ZWO states that plainly. Shooting one-shot-colour through a refractor with nothing in the train means infrared focuses at a different point than visible light and softens the image. Use the D25 UV IR-Cut instead, or filter in the train\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNot a threaded filter.\u003c\/strong\u003e It is a bare optical window that only works installed inside the camera body\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eReplacement means opening the sensor chamber.\u003c\/strong\u003e Dust introduced during the swap lands on or near the sensor — work in still, clean air\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFits 25 mm bodies only.\u003c\/strong\u003e Check your camera against the list above before ordering\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSold as a single window.\u003c\/strong\u003e No tools, gaskets, or retaining ring included\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\u003eWhich cameras use the D25 AR window?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe ASI174 series. The ASI485MC also ships with it from the factory.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat is the difference between the AR window and the UV IR-cut window?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe AR window is anti-reflective coated but optically clear — it passes ultraviolet and infrared through to the sensor. The UV IR-cut window blocks both. ZWO confirms directly that the AR window does not cut UV.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eShould I choose AR or IR-cut?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eIf you filter in the imaging train, or you image in infrared, keep the AR window. If you shoot one-shot-colour with nothing in the train, the IR-cut version does that job at the sensor and frees a filter slot.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eI have an ASI485MC and want IR-cut — what do I order?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe D25IR-CUT. ZWO names it as the correct IR-cut replacement for that camera.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDoes the window have to face a particular direction?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eNo. ZWO confirms there is no specific installation direction.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eMy protective window is scratched — can I just remove it?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe camera will focus and operate without it, but the sensor is then open to dust and humidity, which is a worse problem than the scratch. Replace it.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWill this fit my ASI1600 or ASI294?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eNo. Those bodies use the 32 mm D32 AR window. This is 25 mm.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eIs this good for beginners?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe part is simple; fitting it is not, since it means opening the sensor chamber. If you are not confident working clean, have it done.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eIn short: a 25 mm × 1.1 mm anti-reflective window at 1\/4 λ flatness — the factory spare for the ASI174 series and ASI485MC, and the right choice when you filter in the train or image in infrared. It does not cut UV or IR; if you need that at the sensor, fit the D25 UV IR-Cut.\u003c\/p\u003e","brand":"ZWO Optical","offers":[{"title":"Default Title","offer_id":53804457459823,"sku":"D25AR","price":23.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/f8fc754efe2799ca917eee21d7350efd_cd3116e0-c9d7-41b3-9269-843cf646dcc0.jpg?v=1784083547","url":"https:\/\/ontariotelescope.com\/products\/zwo-d25-ar-protective-window","provider":"Ontario Telescope and Accessories","version":"1.0","type":"link"}