{"product_id":"zwo-asi461mm-pro","title":"ZWO ASI461MM Pro","description":"\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/546449217d7592880418f4af498a0a49.jpg?v=1784081551\" alt=\"ZWO ASI461MM Pro medium format cooled camera with Sony IMX461 sensor, 16-bit ADC, 91% QE and 256MB DDR3 buffer\" style=\"max-width:100%;height:auto;\"\u003e\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eProduct Overview\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThe \u003cstrong\u003eZWO ASI461MM Pro\u003c\/strong\u003e is a medium-format cooled monochrome astronomy camera built around Sony's back-illuminated \u003cstrong\u003eIMX461ALR-C\u003c\/strong\u003e CMOS sensor. At \u003cstrong\u003e44 × 33 mm\u003c\/strong\u003e it carries roughly 70% more imaging area than a full-frame sensor, resolving \u003cstrong\u003e11656 × 8750 — 101.99 megapixels\u003c\/strong\u003e — on a 3.76 µm pixel. A native 16-bit ADC, two-stage TEC cooling to 35 °C below ambient, and zero amp-glow circuitry place this at the top of ZWO's deep-sky camera line.\u003c\/p\u003e\n\u003cp\u003eThis is one of the largest sensors available to amateur astrophotographers, and it is unforgiving of optics that cannot cover it. Read the compatibility notes below before you buy.\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 are imaging \u003cstrong\u003elarge nebulae, sprawling star fields, or extended galactic structure\u003c\/strong\u003e and want to avoid stitching mosaics. The 44 × 33 mm sensor demands optics with an image circle to match — a telescope corrected only for APS-C will vignette badly at these dimensions.\u003c\/p\u003e\n\u003cp\u003eIt is also a sound choice if you are doing \u003cstrong\u003ephotometry or scientific research\u003c\/strong\u003e, where 16-bit linearity, 1.0 e⁻ read noise, and a 50.3 ke⁻ full well matter more than frame rate.\u003c\/p\u003e\n\u003cp\u003eIt is \u003cstrong\u003enot\u003c\/strong\u003e a planetary camera. At 3.77 fps at full resolution, high-frame-rate lucky imaging of Jupiter or the Moon is outside its purpose — use a ZWO planetary camera for that.\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\u003eSony IMX461ALR-C, 44 × 33 mm medium format:\u003c\/strong\u003e back-illuminated CMOS at 3.76 µm pixel pitch, 101.99 MP (11656 × 8750), with a 55 mm sensor diagonal\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNative 16-bit ADC:\u003c\/strong\u003e 65,536 levels, holding tonal separation that a 12- or 14-bit camera cannot\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e50.3 ke⁻ full well capacity:\u003c\/strong\u003e rises to 198 ke⁻ in Bin2 mode with an effective 7.5 µm pixel — useful headroom against saturated star cores\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e1.0 e⁻ read noise:\u003c\/strong\u003e HCG mode engages automatically at gain 100 and drops read noise from roughly 3.1 e⁻ to under 1.5 e⁻ with no meaningful loss of dynamic range\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTwo-stage TEC cooling:\u003c\/strong\u003e 35 °C below ambient, measured at 30 °C ambient temperature\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eZero amp glow:\u003c\/strong\u003e no infrared bloom in uncalibrated corners, even at high gain on long sub-exposures\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePolyimide dew heater:\u003c\/strong\u003e approximately 5 W on the protective window, switchable off in software to conserve power\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUSB 3.0 Type-B with 256 MB DDR3 buffer:\u003c\/strong\u003e 3.77 fps at full resolution with no dropped frames during long reads\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e91% peak quantum efficiency:\u003c\/strong\u003e meaningfully shortens narrowband integration time\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eExposure range 32 µs to 2000 s:\u003c\/strong\u003e rolling shutter, AR-coated D79.3-4 protective window\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e\u003cstrong\u003eOptical \/ Mechanical Design\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eAt 3.76 µm across a 44 × 33 mm chip, the ASI461MM Pro is sampling-hungry rather than fast. Its \u003cstrong\u003e55 mm sensor diagonal exceeds the corrected image circle of most field flatteners\u003c\/strong\u003e, which means corner star quality on this camera is set by your optics, not by the camera. Verify your corrected image circle before committing — a scope advertised as full-frame capable will still fall off in the corners here.\u003c\/p\u003e\n\u003cp\u003eThe camera body measures \u003cstrong\u003eØ106 mm at the front flange, Ø90 mm at the cooling barrel, and 103 mm long\u003c\/strong\u003e. At \u003cstrong\u003e910 g\u003c\/strong\u003e it is light for its format — most quality focusers will carry it without rebalancing the imaging train.\u003c\/p\u003e\n\n\u003ch4\u003e\u003cstrong\u003eHCG mode and gain selection\u003c\/strong\u003e\u003c\/h4\u003e\n\u003cp\u003eRead noise is essentially flat at about 3.1 e⁻ from gain 0 to gain 99, then drops sharply to roughly 1.45 e⁻ the moment HCG engages at \u003cstrong\u003egain 100\u003c\/strong\u003e — while dynamic range actually recovers slightly rather than falling. This is why \u003cstrong\u003eZWO recommends gain 0 or gain 100 for deep-sky imaging\u003c\/strong\u003e and nothing in between: gain 50 costs you read noise for no benefit. Dynamic range peaks near 14 stops at unity and declines steadily with gain thereafter.\u003c\/p\u003e\n\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/c475923fe39773ee78f6a42215def5e3.jpg?v=1784081551\" alt=\"ZWO ASI461MM Pro camera performance charts showing full well, e-gain, dynamic range and read noise against gain with HCG mode engaging at gain 100\" style=\"max-width:100%;height:auto;\"\u003e\u003c\/p\u003e\n\n\u003ch4\u003e\u003cstrong\u003eQuantum efficiency\u003c\/strong\u003e\u003c\/h4\u003e\n\u003cp\u003eAbsolute QE peaks at \u003cstrong\u003e91% near 450 nm\u003c\/strong\u003e and holds above 85% through the blue-green. It falls away steadily through the red — roughly 50% at 700 nm and under 20% beyond 850 nm. In practice this means O-III and H-beta narrowband work is very efficient on this sensor, while deep red and near-IR channels need proportionally longer integration.\u003c\/p\u003e\n\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/481dd5f44a1dc45d6bc8088aa5b9e04d.jpg?v=1784081552\" alt=\"ZWO ASI461MM Pro absolute and relative quantum efficiency curves peaking at 91 percent near 450nm\" style=\"max-width:100%;height:auto;\"\u003e\u003c\/p\u003e\n\n\u003ch4\u003e\u003cstrong\u003eCooling and dark current\u003c\/strong\u003e\u003c\/h4\u003e\n\u003cp\u003eCooling is two-stage, and the 35 °C delta is measured at 30 °C ambient. Expect a smaller delta on a cold night, and smaller again once the cooler has run for several hours — TEC performance is always relative to ambient, never absolute. That behaviour is normal and is not a fault.\u003c\/p\u003e\n\u003cp\u003eThe payoff is real: at \u003cstrong\u003e0 °C sensor temperature dark current is 0.003 e⁻\/s\/pixel\u003c\/strong\u003e, so a 300-second sub accumulates about 0.7 e⁻ of dark noise — less than the camera's own read noise. At \u003cstrong\u003e−20 °C it falls to 0.00024 e⁻\/s\/pixel\u003c\/strong\u003e, which is negligible by any practical measure. ZWO does not recommend operating the camera below −20 °C.\u003c\/p\u003e\n\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/f0222898d56617529e035d220926eca1.jpg?v=1784081551\" alt=\"ZWO ASI461MM Pro two-stage TEC cooling dark current chart from -20C to 30C sensor temperature\" style=\"max-width:100%;height:auto;\"\u003e\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eRecommended Uses\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eWide-field deep-sky imaging\u003c\/strong\u003e of large emission nebulae — the Veil, the North America Nebula, the Rosette — in a single frame rather than a mosaic\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLRGB and narrowband imaging\u003c\/strong\u003e through a filter wheel, where monochrome sensitivity and 91% QE pay for themselves\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMilky Way core and star-field work\u003c\/strong\u003e at short focal lengths where the 44 × 33 mm frame is fully illuminated\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePhotometry and scientific imaging\u003c\/strong\u003e requiring 16-bit linearity and a well-characterised low-noise sensor\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eObservatory installations\u003c\/strong\u003e where the camera is permanently mounted with dedicated 12 V power\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\u003eFront thread:\u003c\/strong\u003e M68 × 1 female, for direct connection to a focuser or ZWO's M68 accessory chain\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBackfocus:\u003c\/strong\u003e 22.5 mm from the front flange (17.5 mm in the alternate configuration) — confirm which your imaging train requires before ordering spacers\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFilter wheels:\u003c\/strong\u003e a monochrome sensor needs filters. The matched chain is \u003cstrong\u003eOAG-L-68 → darkening ring set (D90×D72×T0.2) → EFW 7×50 mm → camera\u003c\/strong\u003e. Filters smaller than 50 mm will vignette a 55 mm sensor diagonal\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOff-axis guiding:\u003c\/strong\u003e the ZWO OAG-L-68 is the correct size for this format and threads directly into the chain above\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePower:\u003c\/strong\u003e requires a 12 V DC supply at 3 A minimum, 5.5 × 2.1 mm barrel, centre-positive. Not included\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSoftware:\u003c\/strong\u003e Windows, Linux, and macOS. Works with ASIAIR, N.I.N.A., SharpCap, and other ASCOM-compatible platforms\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOperating range:\u003c\/strong\u003e −5 °C to 50 °C, 0–80% relative humidity\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/a320604e911b80c02e76fff1955654b4.jpg?v=1784081551\" alt=\"ZWO ASI461MM Pro structural dimension diagram showing 22.5mm backfocus, M68 thread, and OAG-L-68 to EFW 7x50 filter wheel spacing chain\" style=\"max-width:100%;height:auto;\"\u003e\u003c\/p\u003e\n\n\u003ch4\u003e\u003cstrong\u003eWhat's in the box\u003c\/strong\u003e\u003c\/h4\u003e\n\u003cp\u003eASI461MM Pro camera body, padded camera bag, USB 3.0 cable (2 m), two USB 2.0 cables (0.5 m), and a quick guide. \u003cstrong\u003eThe 12 V power supply is not included\u003c\/strong\u003e and is required for operation.\u003c\/p\u003e\n\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/9e024675eec69a870288d6b98e80a78e.jpg?v=1784081553\" alt=\"ZWO ASI461MM Pro box contents showing camera body, camera bag, USB 3.0 cable, two USB 2.0 cables and quick guide\" style=\"max-width:100%;height:auto;\"\u003e\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eImportant Limitations\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eRequires external 12 V DC power at 3 A minimum.\u003c\/strong\u003e USB alone will not run the TEC cooler — the camera will not operate correctly powered from a computer port or an ASIAIR hub. The power supply is not included\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSupply voltage outside 11–15 V risks irreparable damage\u003c\/strong\u003e to the camera\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDo not operate below −20 °C sensor temperature\u003c\/strong\u003e — ZWO advises against it, and there is no measurable dark-current benefit below that point\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNot suitable for planetary or lunar high-frame-rate imaging\u003c\/strong\u003e — 3.77 fps at full resolution\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDemands optics corrected for a 55 mm image circle.\u003c\/strong\u003e Smaller corrected circles will vignette\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMonochrome only\u003c\/strong\u003e — colour imaging requires a filter wheel and an LRGB or narrowband filter set, sold separately\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNot a beginner's first camera.\u003c\/strong\u003e The sensor size, filter requirements, and power demands assume an established imaging setup\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 the ZWO ASI461MM Pro good for beginners?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eNo. It is a specialist medium-format camera that requires a filter wheel, dedicated 12 V power, and optics corrected for a 55 mm image circle. If you are starting deep-sky imaging, a cooled one-shot-colour camera on an APS-C sensor is a far better first step.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat gain should I use for deep-sky imaging?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eGain 0 or gain 100, and nothing in between. Read noise stays around 3.1 e⁻ right up to gain 99, then drops to roughly 1.45 e⁻ the instant HCG mode engages at 100. Intermediate gains cost read noise and return nothing.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat is HCG mode?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eHigh Conversion Gain. It switches on automatically at gain 100 and cuts read noise by more than half while leaving dynamic range essentially unchanged. You do not need to enable it manually.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat is the ASI461MM Pro best used for?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eWide-field deep-sky imaging of large targets in a single frame, and narrowband work where monochrome sensitivity and 91% QE shorten integration time. It is also well suited to photometry and research imaging.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCan I use it for planetary imaging?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eNot effectively. At 3.77 fps at full resolution it cannot capture the frame rates that lucky imaging depends on.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat backfocus does it need?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003e22.5 mm from the M68 × 1 front flange, or 17.5 mm in the alternate configuration.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhich filter wheel and off-axis guider should I pair with it?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe ZWO EFW 7×50 mm and the OAG-L-68, assembled as OAG-L-68 → darkening rings → EFW → camera. Filters under 50 mm will vignette the 55 mm sensor diagonal.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDoes it need a separate power supply?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eYes. A 12 V DC supply at 3 A minimum (5.5 × 2.1 mm, centre-positive) is required and is not included. USB will not power the cooler.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat telescope do I need for a 44 × 33 mm sensor?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eOne with a corrected image circle of at least 55 mm. Many refractors marketed as full-frame capable will still show corner fall-off at this diagonal — check the corrected circle, not the marketing claim.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eHow does it compare to the ASI6200MM Pro?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe ASI6200MM Pro uses a 36 × 24 mm full-frame sensor at 62 MP. The ASI461MM Pro is larger at 44 × 33 mm and 102 MP, with the same 3.76 µm pixel — so it gives more field at the same image scale, at the cost of demanding much more from your optics.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhy is my cooling delta less than 35 °C?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThat figure is measured at 30 °C ambient. Delta T falls as ambient temperature falls and after the cooler has run for an extended period. This is expected behaviour for any TEC-cooled camera.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eHow long can I expose before dark current matters?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eAt 0 °C, a 300-second sub accumulates roughly 0.7 e⁻ of dark noise — below the camera's read noise. At −20 °C dark current is effectively negligible. Read noise, not dark current, is your limiting factor on this sensor.\u003c\/p\u003e\n\n\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eIn short: a 102 MP medium-format monochrome sensor for imagers whose optics can genuinely cover 44 × 33 mm. Budget for a 12 V 3 A supply, an EFW 7×50 mm filter wheel, and glass corrected for a 55 mm image circle. Run it at gain 0 or 100 and cool it to 0 °C or below. Get those right and this is among the most capable deep-sky cameras available to amateurs.\u003c\/p\u003e","brand":"ZWO Optical","offers":[{"title":"Default Title","offer_id":53804206063727,"sku":"ASI461MM-P","price":16243.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/1ddbd9688dd74a17774927a0b11e925c-1.jpg?v=1784081170","url":"https:\/\/ontariotelescope.com\/products\/zwo-asi461mm-pro","provider":"Ontario Telescope and Accessories","version":"1.0","type":"link"}