ZWO EFW-7×36 mm (EFW-7x36-25)

Electronic Filter Wheel · 7 Positions · 36 mm Unmounted Filters · USB-C

Designed for serious deep-sky imagers using APS-C and full-frame monochrome cameras, the ZWO EFW-7×36 mm provides seven precisely indexed filter positions in ZWO’s newest EFW-25 housing. This next-generation design merges advanced light-leak control, a rigid CNC-machined chassis, and quiet, dependable stepper-motor rotation—all in a slim body engineered for clean, flat-field illumination with 36 mm unmounted filters.

For imagers running LRGB, SHO, and an additional specialty filter, this wheel gives you the capacity to load an entire workflow at once, reducing setup time and keeping your imaging train sealed, aligned, and automated.

Improved Light-Leak Protection for High-Quality Calibration Frames

The EFW-25 series introduces ZWO’s redesigned light-blocking system:

• Refined slot-fit chassis for a tighter seal between the front and rear plates

• Dual light-blocking pads at critical side interfaces

• Fully enclosed motor compartment preventing light ingress and improving dust resistance

These upgrades help maintain uniform flats and consistent background levels—especially important when shooting narrowband filters on large sensors, where gradients are easier to detect.

Seven-Position Carousel for 36 mm Unmounted Filters

Ideal for APS-C and many full-frame imaging setups, the wheel accepts:

• Seven 36 mm unmounted filters

This configuration provides complete coverage for LRGB + SHO + optional extra filters such as IR, continuum, or luminance variations.

The internal disk is machined from 6061 aluminum alloy, giving the wheel excellent rigidity with minimal weight.
Despite its larger format, the wheel maintains a slim ~20 mm thickness, helping preserve backfocus in imaging trains using OAGs, tilt plates, and reducers.

Power, Connectivity & Software Integration

The EFW-7×36 mm uses a single USB-C port for power and control:

• Power draw: ~120 mA at 5V

• Cables included: 0.5 m & 2 m USB-A to USB-C

• No external 12V supply required

Fully supported by:

• ASIAIR

• ASIStudio

• ASCOM drivers

• ZWO SDK-based imaging software

The internal high-precision stepper motor offers accurate, bidirectional indexing for fully automated workflow integration.

Compatibility

This wheel is an ideal match for:

• ASI2600MM Pro (APS-C monochrome)

• ASI533MM Pro

• ASI071 / similar APS-C sensors

• Fast refractors where 36 mm filters prevent vignetting

• Systems requiring compact spacing around a ZWO OAG or tilt adapter

Compatible with the entire line of ZWO 36 mm unmounted filters.

What’s in the Box

(Based on standard EFW-25 packaging; exact contents may vary slightly by model.)

• EFW Body

• 36 mm Filter Masks

• Threaded Adapter (M54 or M42 configuration depending on kit)

• M2, M2.5, and M4 Screw Assortments

• 3×75 mm Phillips Screwdriver

• Mounting Bracket

• USB 2.0 Cable (2 m)

• USB 2.0 Cable (0.5 m)

Imaging Tip

When installing 36 mm unmounted filters, always use the included masks to center each filter precisely. Proper alignment ensures optimal edge illumination—especially critical for APS-C sensors where even slight decentering can create off-axis gradients. After installing your filter set, run a full flat-calibration sequence to confirm uniform response across all seven positions.