The ZWO ASI533MM is a compact, uncooled monochrome camera designed for planetary imaging, lunar work, and electronically assisted astronomy (EAA). It’s based on Sony’s highly acclaimed IMX533 monochrome sensor, which offers exceptional sensitivity, a square format, and zero amp glow—even during long exposures. This makes it a powerful tool for beginner and intermediate astrophotographers seeking clean, high-resolution images without the complexity of cooling systems.

Sensor Technology & Format

At the heart of the ASI533MM is the Sony IMX533 mono sensor, a 1″ format CMOS chip with a 15.99mm diagonal and a square 3008×3008 pixel array, delivering a total of 9 megapixels. With a 3.76μm pixel size, it strikes an excellent balance between detail and signal collection—ideal for telescopes with short to medium focal lengths.

The sensor features Sony’s STARVIS back-illuminated technology, which greatly enhances sensitivity by allowing more light to reach the photodiodes. This design dramatically improves low-light performance while keeping read noise to a minimum. As a result, the camera delivers outstanding contrast and resolution, especially under poor lighting or narrowband filter use.

Quantum Efficiency & Signal Response

The ASI533MM reaches an impressive peak quantum efficiency (QE) of 91% at 460nm, meaning it captures a large percentage of incoming light and converts it directly into signal. This high QE ensures excellent performance in both broadband and narrowband imaging, allowing users to detect faint features in nebulae, galaxies, and planetary surfaces with shorter exposures.

Dark Current and Read Noise

The dark current of the ASI533MM is extremely low, making it well suited for imaging faint targets with longer exposures—even without a cooling system. Combined with its low read noise and clean signal path, the camera ensures you get high-quality frames with excellent detail and contrast.

DDR3 Buffer & High-Speed USB 3.0

To maintain stable and reliable performance during image capture, ZWO has equipped the ASI533MM with a 256MB DDR3 memory buffer. This onboard RAM improves data throughput and eliminates frame dropouts—particularly useful when running the camera at high speed or using longer exposures in live stacking software.

The camera also features a USB 3.0 interface, providing 5Gbps bandwidth and allowing it to run at 20 frames per second at full 9MP resolution. This speed is especially useful for planetary imaging, where you can capture many frames in a short time and stack them to enhance image sharpness and detail.

Clean Imaging – Zero Amp Glow Circuitry

Traditional CMOS sensors often suffer from amp glow—a subtle infrared glow that appears in one corner of the frame during long exposures or high gain. The ASI533MM completely eliminates this issue thanks to ZWO’s zero amp glow circuitry. Even with 300-second exposures, the ASI533MM produces a clean, glow-free frame—meaning less time spent on calibration and cleaner stacked results.

Ideal Applications

• Planetary imaging – Sharp, fast captures of Jupiter, Saturn, and the Moon

• Lunar mosaics – Square sensor format is ideal for tiling large lunar scenes

• EAA and live viewing – Clean, fast images with minimal noise

• Narrowband imaging (with filters) – Excellent QE and no amp glow

Mechanical Diagram