ZWO T2-1.25" Filter Adapter

The adapter is 3 mm thick and, as ZWO's photo shows, threads into the camera's front T2 port, so the filter sits just in front of the sensor. ZWO does not publish a separate optical length figure for it; like any filter, the glass itself shifts focus slightly.

Yes. The adapter uses the universal M42 (T2) thread standard on the camera side and accepts any standard 1.25" astronomy filter. It is compatible with any T-threaded astronomy camera and any brand of 1.25" filter.

No, this adapter is designed as an alternative to a filter wheel for single-filter applications. It threads into the camera's front T2 port, so the 1.25" filter sits inside the optical train near the sensor, which prevents vignetting. It is ideal for monochrome guide cameras or for color cameras where you only need to add a single light pollution or UV/IR cut filter.

The primary advantage is rigidity. A direct M42 thread connection prevents the tilt and sag that can occur with a nosepiece held in place by thumbscrews. This secure, parallel connection is crucial for avoiding image degradation, especially with sensitive optical systems.

Absolutely. For planetary, lunar, or solar imaging with a one-shot-color camera like the ASI178MC, adding a single UV/IR cut filter is critical for sharp focus. This 3 mm adapter provides the most secure and lowest-profile method to do so without altering your setup significantly.

The adapter has four small holes on its face. While it can often be tightened by hand, if you need extra leverage, you can use a spanner wrench or the tips of a small pair of needle-nose pliers inserted into two opposing holes to gently secure it to your camera body.