ZWO
ZWO ASI533MM Pro
A square-sensor monochrome camera that makes narrowband imaging affordable, the friendly on-ramp to mono and filters.
90/ 100
Camera Type
PlanetaryDeep sky
Built for deep sky, nebulae, galaxies and clusters under long exposure. Capable on the Moon, but oversized for high-resolution planets.
Type
Monochrome
Cooling
−35°C
Pixel Size
3.76µm
Read noise
1.0 e⁻
Resolution
9 MP · 3008×3008
Sensor
Sony IMX533 · 1"
From$999
$100 above 90-day low
Price tracked by PolarisObserved 53 timesTracking since Jul 2026
The frame it captures
Same camera. Different telescope. A completely different photograph.
A camera has no field of view of its own, the telescope in front of it decides everything. Pick a target and watch the same 9-megapixel frame become three different images.
Fills the frame edge to edge, the classic full-galaxy portrait.
Only the bright core fits; the spiral arms spill off the sensor.
Only the bright core fits; the spiral arms spill off the sensor.
01What it's good at
What it's best at — and the trade-offs.
Best at
✓Amp-glow-free IMX533 keeps mono calibration simple.
✓A square sensor frames narrowband targets the same at any rotation.
✓Low read noise and high QE make short narrowband subs viable.
Trade-offs
!Needs filters and a wheel like any mono camera.
!A 1-inch sensor frames a smaller field than APS-C mono.
!9 MP is lower resolution than the larger IMX571.
02In plain English
The numbers, in plain English.
Read noiseExcellent
1.0 e⁻
One electron of added noise per readout means faint signal survives in short subframes, which matters doubly in mono narrowband work where each filter already throws away most of the incoming light.
Pixel sizeBalanced
3.76 µm
A middle pixel size suited to the 400 to 1000 mm focal lengths most amateur telescopes offer, sampling finely enough for detail without starving each pixel of light.
SensorSquare
Sony IMX533, 1 inch square
The square format frames identically at any rotation, which simplifies planning when you are shooting the same target through several filters across several nights. The compact size also keeps corner correction easy.
CoolingRegulated TEC
35 C below ambient
Deep regulated cooling is essential for the long exposures narrowband imaging needs, and the repeatable temperature keeps a dark library valid rather than forcing fresh calibration every session.
Full wellDynamic range
50,000 e⁻
A deep well protects bright cores from clipping during the long exposures this camera is built for, preserving detail you would otherwise have to recover from a separate short-exposure set.
Peak QESensitivity
About 91 percent
Without a colour filter array over the pixels, every pixel receives all the light that reaches it and over ninety percent of it is recorded. That efficiency is the reason mono cameras out-resolve colour ones of the same size.
03Typical targets
What it shines on.
04Build your imaging rig
Everything you'd actually buy.
Capture
The scope that forms the image
Sky-Watcher Esprit 100EDX
550 mm f/5.5 apo, a flat, fast field that suits this sensor.
Track
What holds it steady
A tracking equatorial mount
Long exposures need a solid, guided EQ mount underneath.
Complete it
What unlocks its range
Filter wheel + LRGB/narrowband filters
Mono needs filters; a motorised wheel automates the sequence.
02The Polaris Score
How it scores, and why.
90/ 100
ZWO ASI533MM Pro
#1 of 7 mono deep-sky cameras
The easiest and cheapest way into serious narrowband: low read noise, no amp glow and a forgiving square field, at the cost of a smaller frame.
Image quality92
Low-light sensitivity93
Ease of use78
Value90
Polaris weighs how well the camera does the job it was designed for — image quality, sensitivity, versatility and value — never list price or brand.
03Who it's for
An honest fit check.
Buy it if you
✓Imagers ready to move up to filters for higher resolution and true narrowband.
✓Chase the Ha/OIII/SIII palette on emission nebulae from light-polluted skies.
✓Want the deepest luminance detail a sensor of this size can give.
✓Are comfortable running a filter wheel and a longer capture sequence.
Look elsewhere if you
!Beginners who want a fast, simple one-shot-colour path to an image.
!Anyone unwilling to buy and run filters and a wheel.
!Planetary-only imagers.
!People without a guided equatorial mount.
05The numbers
Full specifications.
Sensor
ModelSony IMX533
TypeCMOS · 1"
Megapixels9
Pixel Size3.76µm
Bit depth14-bit ADC
Noise & sensitivity
Read noise1.0 e⁻
Full well50,000 e⁻
Peak QE~91%
Dynamic range14 stops
Cooling
Cooling−35°C
Connectivity & fit
InterfaceUSB 3.0
Weight0.42 kg
More
cooledtrue
Sensor Height11.3mm
Sensor Width11.3mm
Editor’s Take
It brings the clean, amp-glow-free IMX533 to mono, so you can learn filters and narrowband without the cost of an APS-C rig. A superb first mono camera.
— The Skynocular verdict
06Alternatives