Most astronomy cameras are rectangular because they’re designed to do a little of everything. The ASI676MM is different. It’s square — a 3552 × 3552 monochrome sensor built specifically for all-sky imaging, meteor patrol, and full-disk lunar and solar work. Bolt it to a fisheye lens, point it up, and let it run. Meteors leave clean traces across the full frame, not just the long axis. Mosaics stitch without you doing trig on which side is the long side. Twelve megapixels of detail captures the Sun in white light, the Moon at full disk, and a noctilucent cloud event you weren't expecting — all from the same rig.
A Square Sensor Built for the Whole Dome
The IMX676 uses a square sensor format. For all-sky imaging through a fisheye, the circle of illumination fits a square frame far better than a rectangle, wasting fewer pixels on black corners. For meteor patrols, a streak traveling any direction across the sky is captured at full resolution rather than clipped along the short axis. For mosaics, you stop having to think about which way to rotate each tile. The geometry is the feature.
What the 676MM Is — and What It Isn't
The ASI676MM pairs Sony's IMX676 back-illuminated STARVIS 2 monochrome sensor with USB 3.0, a 256MB DDR3 buffer, and no cooler. The sensor is 1/1.6 inches, 7.1mm × 7.1mm, and — unusually — perfectly square. Resolution is 12.6 megapixels (3552 × 3552), with 2.0-micron pixels feeding a 12-bit ADC. Quantum efficiency peaks at 83%. Read noise drops to 0.56 electrons in HCG mode, which engages automatically at gain 180 and keeps dynamic range close to 11 stops. Full well sits at 10.55 kiloelectrons. Maximum frame rate is 31.2 fps at the full 12MP — slower than a dedicated planetary camera, faster than anything you need for meteor work or time-lapse.
The protective window is AR-coated rather than UV/IR-cut, so the sensor sees from the near-UV through to the near-IR. The monochrome design prioritizes maximum spectral sensitivity.
It is not a deep-sky camera. There is no TEC cooler, and the sensor footprint is small for galaxies and nebulae. It is also not the fastest planetary camera in the ZWO line — the ASI678MM gets you 47.5 fps at 4K if pure planetary capture is the goal. What the 676MM does is sit between those two jobs and own a third one: the whole-sky view, the meteor patrol, the mosaic tile, the high-resolution lunar or solar full-disk frame. Very few astronomy cameras are optimized specifically for full-dome imaging. This one is.
What's Included
- ZWO ASI676MM camera body with AR-coated protective window (21mm × 1.1mm)
- USB 3.0 data cable (USB 2.0 compatible at reduced frame rate)
- USB 2.0 ST4 guide cable
- 2" nosepiece adapter for standard 2" focusers
- M42-to-1.25" adapter
- Protective dust cap
- Quick-start guide and driver download instructions
- 256MB DDR3 internal buffer (factory-installed)
Features
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Square 1/1.6" sensor — a format built for the job. The circle of illumination from a fisheye fits a square frame far better than a rectangle. Meteor streaks land at full resolution regardless of direction. Mosaics tile without rotation math.
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STARVIS 2 sensitivity, near-UV to near-IR. The AR-coated window passes a broader spectrum than the UV/IR-cut filter found on the color ASI676MC — opening the door to narrowband Hα, OIII, and methane-band work, plus white-light solar imaging behind a proper filter.
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0.56-electron read noise in HCG mode. High Conversion Gain engages automatically at gain 180. On a 12.6MP square sensor, that noise floor is the difference between detecting a faint meteor or airglow event and recording a blank frame.
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12.6 megapixels at 31.2 FPS. Enough bandwidth for any monitoring task you'll throw at it, and enough resolution for short-burst lunar and solar imaging on small refractors with full disks fitting neatly inside the square frame.
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256MB DDR3 buffer. Absorbs hiccups in your capture chain — laptop spikes, USB renegotiations, software pauses — without dropping frames. Critical for unattended Raspberry Pi or mini-PC operation.
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USB 3.0 with USB 2.0 fallback. Full frame rate on USB 3.0, reduced frame rate on USB 2.0 — honest engineering. ST4 port handles auto-guiding duty between meteor showers.
Under the Night Sky
Set up the ASI676MM with a 2.5mm fisheye lens in a weatherproof enclosure on a back deck or observatory roof and the first clear night explains the camera immediately. A faint Perseid clips through Cassiopeia, a satellite flares near zenith, an airliner crosses Cygnus — every motion across the dome gets recorded at the same resolution, because the square frame doesn't favor a direction. The next morning's stack of 30-second subs is a single composite of the entire night, with every meteor preserved as a clean streak.
Move the camera to prime focus on a small refractor — say a 60mm or 70mm scope — and the same sensor becomes a high-resolution full-disk Sun camera behind a proper white-light filter. The 7.1mm square format fits the solar disk at typical short focal lengths without cropping a limb. Sunspots resolve to fine detail at 2-micron sampling. Do the same with the Moon through a 400–600mm focal length scope and the entire lunar disk lands inside the frame, no mosaic required.
For aurora work, time-lapse, or noctilucent cloud monitoring, the broad spectral response of the AR window pays off. You see the same range your eye does, plus the near-UV and near-IR your eye misses. Twelve megapixels gives you crop room. A single 12-hour all-sky run produces a stack that a rectangular sensor would have to fight for.
For mosaic deep-sky imaging on a longer scope, the square tiles fit together without rotation math. You can plan a 4 × 4 mosaic of the Veil Nebula complex knowing each tile is the same on every side. That's not flash. It's just less friction.
Observing Tip
For continuous all-sky operation, run the camera at gain 200–250 to keep HCG mode active, set exposure to 20–30 seconds, and let it record continuously to a local SSD. Stack the night into a single image the next morning to log every meteor and bright satellite — or feed the stream into open-source meteor-detection software (UFOCapture, RMS, or Meteotrack) for automated event logging. For solar or lunar full-disk work, drop to gain 0 and expose for a histogram peak around 75% of saturation. The square frame simplifies composition decisions considerably.
Frequently Asked Questions
Is this a deep-sky camera?
No, and we wouldn't position it that way. The sensor is uncooled and the 7.1mm square format is small for typical DSO work. If deep-sky is the goal, the cooled ASI533MM (also square but Peltier-cooled) or the larger ASI2600MM Pro are the right choices. The 676MM is built for all-sky, meteor, continuous all-sky monitoring, mosaic, and full-disk Sun/Moon imaging.
What's the difference between this and the ASI676MC?
The MC is the color variant — same sensor, with a Bayer matrix and a UV/IR-cut window. The MM strips both away. You get full monochrome sensitivity, wider spectral response from near-UV through near-IR, and the freedom to put any filter you want in front of it. For serious meteor monitoring, narrowband solar imaging, or any application where you want every photon the sensor can record, the MM is the right call. For casual color all-sky time-lapse, the MC saves you the filter-wheel step.
Why not the ASI678MM instead?
Different camera, different job. The 678MM is rectangular (3840 × 2160) and faster (47.5 fps) — a dedicated planetary imager. The 676MM is square (3552 × 3552), slightly slower (31.2 fps), and designed for whole-sky work. If you want to image Jupiter at 250x in the planetary observatory, get the 678MM. If you want to image the entire sky from your back deck, get the 676MM. Some imagers eventually own both.
Does it need a filter wheel?
Not for all-sky or meteor work. For narrowband solar (Hα), white-light solar (a proper front-aperture filter), or scientific narrowband imaging, you'll want filters — either threaded into the optical train or in a small filter wheel. The ZWO EFW Mini 5×1.25" works well for one-camera-multi-filter setups.
Will it work as a guide camera?
Yes, it has an ST4 port and the resolution and sensitivity are more than sufficient. It's overkill for the job, but if you already own one and want to redeploy it during the daytime, it works.
How does it handle dew and condensation in an outdoor enclosure?
The body itself is sealed, but as with any all-sky camera, the enclosure window will dew if you don't add heat. A small dew heater strip around the enclosure window — or a heated optical port — solves it. Call us and we can recommend a setup that fits.
Accessories
Fisheye or Ultra-Wide Lens — The point of an all-sky camera. CS-mount and C-mount fisheye lenses in the 2.5mm to 6mm range are the standard pairing. A 2.5mm f/1.4 fisheye gets you the full hemisphere with margin.
Weatherproof All-Sky Enclosure — A clear acrylic dome on a sealed housing, ideally with a small fan or dew heater for the optical window. Several aftermarket options exist for the 676 form factor.
ZWO EFW Mini 5×1.25" Filter Wheel — For narrowband solar (Hα, calcium-K), broadband filters, or quick swaps between R/G/B for occasional color mosaics. Connects natively to the camera through ASCOM or ASIAir.
ASIAir Plus or Mini — Untethers the camera from a laptop entirely. Useful for unattended observatory operation or a permanently mounted all-sky rig.
White-Light or Hα Solar Filter — Required for any solar work. A proper front-aperture solar filter on the scope or lens — never an eyepiece-end filter. We carry both glass and polymer options sized for the small refractors that pair well with this sensor.
Dew Heater for the Enclosure Window — The single most-overlooked accessory in unattended outdoor all-sky operation. A 5-watt strip and a controller will save your data.
Final Thoughts
The ASI676MM solves a problem most monochrome cameras don't bother with: how do you watch the whole sky efficiently, with no wasted geometry, no amp glow, no fight with your software, and no fragile cooler hanging off the back? The answer is a square sensor, STARVIS 2 sensitivity, hardware-level glow suppression, and the freedom to point it through a fisheye for meteors or a small refractor for the full Sun without changing camera bodies. It is not the camera you reach for to image the Andromeda Galaxy. It is the camera you reach for when you want to know what happened over your sky last night, end to end. For meteor sections, observatory all-sky stations, satellite-flare logging, full-disk solar science, and any imager who wants one mono camera that does the whole-dome job — this is just what you're looking for.
