Refined Design · Anti Light-Leak Protection · Built for Astrophotography
The upgraded ZWO EFW 8 x 31.75 mm (1.25″) / 31 mm electronic filter wheel delivers exceptional performance for deep-sky astrophotographers. Featuring a re-engineered internal mechanism, modern USB-C connection, and structural improvements, it provides silent, reliable, and completely light-tight filter switching during demanding imaging sessions.
Comprehensive Anti Light-Leak Architecture
In deep-sky imaging, even minuscule amounts of stray light can introduce gradients or ruin long exposures. The updated ZWO EFW tackles this with three key engineering enhancements:
- Upgraded Sealing Structure: A slot-fit chassis ensures a tight mechanical bond between top and bottom covers.
- Dual Light-Blocking Pads: Positioned at lateral connection points to eliminate optical leaks.
- Enclosed Motor Compartment: Fully sealed motor unit protects against environmental dust and light reflections.
USB-C Interface & Low Power Draw
Say goodbye to fragile USB Type-B connectors. The modern USB-C port provides a secure and durable physical link. Operating entirely on 5V USB power with a minimal current draw of ~120 mA, it can be powered directly through the USB hub of your cooled ASI camera or ASIAIR unit without needing extra power cables.
Aircraft-Grade Lightweight Construction
Machined via high-precision CNC from an aircraft-grade aluminum block, the outer body measures only 20 mm (0.79 in) in thickness and weighs approximately 400 g (14 oz) bare / 530 g (1.17 lbs) fully configured. The interior filter carousel is constructed from 6061-T6 aluminum alloy, offering maximum rigidity and minimal rotational inertia.
Technical Specifications
| Parameter | Specification Details |
|---|---|
| Model | ZWO EFW 8 x 31.75 mm (1.25″) / 31 mm (ZWO-EFW-8x1.25) |
| Filter Capacity | 8 Positions |
| Supported Filter Types |
• 31.75 mm (1.25″) Mounted filters (cell thickness ≤ 7 mm / thread height < 3 mm) • 31 mm Unmounted filters (thickness 1.5 mm – 3.5 mm) |
| Effective Optical Thickness | 20 mm (0.79 in) |
| Weight | 400 g (14 oz) [Wheel Body] / 530 g (1.17 lbs) [Gross Weight] |
| Material | CNC-machined Aircraft Aluminum / 6061 Carousel |
| Motor Unit | High-precision NPM Stepper Motor (Japan), Bidirectional Rotation |
| Power Requirement | 5V DC, ~120 mA (Powered via USB) |
| Data Interface | USB-C (Includes 2 m / 6.56 ft USB 2.0 Type-A to Type-C Cable) |
| Vignetting Limits | No vignetting down to F/5 for 31.75 mm (1.25″) filters; down to F/2 for 31 mm unmounted filters (tested on ASI1600) |
| Software Compatibility | ASIAIR, ASIStudio, ASCOM drivers, ZWO Native SDK (Driver-free operation) |
What's in the Box?
- 1x ZWO 8x31 mm EFW Main Body
- 1x 31.75 mm (1.25″) Dust Cover
- 1x T2 Nosepiece
- 1x 31.75 mm (1.25″) Holder (with cover & 2 screws)
- 1x T2-T2 Male Adapter
- 1x Bag of Filter Masks
- 1x USB 2.0 Cable (2 m / 6.56 ft)
- 1x Phillips Screwdriver
- 1x Bag of M2 Screws and Washers
Filter Installation Guide
Filter requirement: Thread length < 3 mm (0.12 in), total cell height < 7 mm (0.28 in).
- Remove the back cover of the EFW.
- Lay the wheel flat on a clean surface.
- Gently screw the mounted filters into the threaded positions.
- Reattach the back cover firmly.
Filter requirement: Thickness between 1.5 mm and 3.5 mm.
- Remove the back cover and place the EFW flat.
- Carefully place 31 mm filters into the recessed slots holding them by the edges.
- Secure each filter using the provided M2 screws and protective washers.
- Reattach the back cover.
Frequently Asked Questions & Troubleshooting
- Filter Cell Too Thick: Ensure mounted filters are thinner than 7 mm (0.28 in) excluding threads, and thread length is under 3 mm (0.12 in).
- Screw Protrusion: Check if the M2 screws securing unmounted filters are overtightened or too long.
- Adapter Protrusion: Verify that the M42/T2 threads from your telescope adapter or camera do not extend too deep into the wheel chassis (exceeding 3.5 mm).
| Brand | ZWO |