ZWO Duo camera's and compatible image circles

Maximize Performance with the Right Image Circle for Your ZWO ASI2600 and ASI585MC Air Cameras

If you're using one of the latest ZWO ASI Air cameras, like the ASI2600MC Duo, ASI2600MC/MM Air, or the highly versatile ASI585MC Air, you're already working with some of the most advanced astrophotography tools available today. These cameras combine powerful sensors with the wireless convenience of the ASIAIR platform, making deep-sky imaging more streamlined than ever. But to fully unlock their performance, there's one critical factor to understand: image circle compatibility.

What Is Image Circle and Why Does It Matter?

The image circle refers to the area of light your telescope can project onto a camera sensor. If your telescope’s image circle is smaller than your camera’s sensor size, or doesn’t fully cover both the main and guiding sensors, you may experience vignetting, star distortion, or guiding errors. This is especially important with cameras like the ASI2600MC Duo, which includes an off-axis guiding sensor built into the camera body.

ASI2600MC/MM Air: Best with Full-Frame Image Circles

The ZWO ASI2600MC and MM Air cameras feature large APS-C sensors with a diagonal of 28.3mm. However, due to the position of the built-in guide sensor in the Duo version, the system requires a full-frame image circle (Φ43mm) for optimal performance. If you're using a telescope designed only for APS-C coverage, the guide star may appear slightly distorted or lose brightness near the edge of the field. For critical guiding accuracy, ZWO recommends telescopes that support full-frame imaging.

ASI585MC Air: Compact, But Still Needs Wide Coverage

The ASI585MC Air, while featuring a smaller sensor, still requires a 36mm image circle to ensure both the main sensor and guide sensor are properly illuminated. Although the primary sensor is well within APS-C range, the guide sensor sits above it, meaning the image circle must extend further than expected.

Telescope Recommendations for ZWO Air Cameras

To get the most out of your ZWO ASI2600 or ASI585MC Air camera, pair it with a telescope that offers at least APS-C, and ideally full-frame, image circle coverage. Popular choices include:

• Starfield GEAR Series Apochromatic Refractors

• Sharpstar and Askar full-frame-ready astrographs

• Telescopes with dedicated full-frame flatteners or reducers.  A 48mm output thread is required generally.

Final Thoughts: Avoid Guiding Distortion and Get Sharper Stars

The ZWO ASI Air cameras are engineered for convenience, precision, and quality. But using them with a telescope that doesn't support the required image circle can limit their potential. By ensuring your telescope supports the correct image circle size, you'll enjoy cleaner stars, improved guiding, and overall better imaging performance.

If you're unsure whether your telescope is compatible with the ASI2600MC/MM or ASI585MC Air, contact us. We’re happy to help match you with the perfect optics for your astrophotography setup.