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Seven 2-inch filters, changed automatically all night
Why we like the ZWO EFW 7x2" (2025):
- Room for a full set: seven slots hold luminance, red, green and blue plus hydrogen-alpha, OIII and SII, so you never have to swap filters by hand mid-session.
- One USB-C cable: it draws only 120mA at 5V, so it runs from the USB hub on a ZWO cooled camera with no separate power supply, and needs no driver.
- Tighter light sealing: the 2025 redesign adds a slot-fit chassis, light-blocking pads and a fully enclosed motor to keep stray light out of long narrowband frames.
- Worth knowing: 2-inch filters cost more than 1.25-inch or 36mm ones. You need them for full-frame sensors like the ASI6200MM Pro; for APS-C cameras they also leave more room for spacing and fast optics.
The ZWO 7-Position Electronic Filter Wheel (EFW 7x2", 2025 model) holds seven 2-inch mounted filters, or 50mm round unmounted filters, and turns them into place on command from your capture software. It's the wheel we pair with ZWO's APS-C and full-frame mono cameras for LRGB and narrowband imaging. The CNC-machined aluminum body is 20mm thick, weighs 720g (1.6lb) and connects over USB-C to an ASIAIR, a computer running ASCOM software, or ZWO's ASIStudio.
Key specs: 7 positions for 2" mounted or 50mm unmounted filters · 20mm optical thickness · M54 × 0.75 threads on both sides · USB-C, 5V at 120mA · driver-free, works with ASIAIR, ASCOM and ASIStudio · anti light-leak sealing · 720g (1.6lb)
What you can image with it
- Narrowband nebulae from the city: hydrogen-alpha, OIII and SII filters for Hubble-palette images of the Eagle, Heart, Soul and Veil Nebulae from a light-polluted backyard.
- LRGB galaxies and clusters: luminance for detail plus red, green and blue for color on targets like the Andromeda and Whirlpool Galaxies.
- Mixed nights: shoot narrowband while the Moon is up and switch to LRGB after it sets, all in one automated sequence.
How it works
Screw the wheel between your camera and the telescope's flattener or reducer using the included M54, M48 and M42 adapters, plug its USB-C cable into the camera's USB hub, and it shows up in your software. A high-precision stepper motor turns the 6061 aluminum carousel in either direction to the next filter, and the software refocuses and continues the sequence.
The wheel takes 20mm of the usual 55mm back focus. ZWO's example layout for an APS-C cooled camera is the camera (12.5mm), this wheel (20mm), a ZWO Large OAG (17.5mm) and a 5mm tilt adapter, which adds up to 55mm.
What to add for the best results
- Optolong LRGB + SHO 7nm filter set, 2" (7 filters): fills all seven slots with one purchase. Or start with the ZWO 7nm SHO set or Optolong SHO 7nm set in 2" for narrowband only.
- A mono camera: the ZWO ASI2600MM Pro (APS-C) or ASI6200MM Pro (full frame).
- ZWO Large OAG (12mm prism) with an ASI220MM Mini: guides through the main scope and completes the 55mm spacing.
- ASIAIR Plus: runs multi-filter sequences with autofocus on each filter change.
- ZWO EAFN electronic focuser: corrects small focus shifts between filters automatically.
EFW 7x2" vs. EFW 5x2"
| EFW 7x2" (2025) | EFW 5x2" (2025) | |
|---|---|---|
| Positions | 7 | 5 |
| Filters | 2" mounted or 50mm unmounted | 2" mounted or 50mm unmounted |
| Thickness | 20mm | 20mm |
| Weight | 720g | 540g |
| Best for | LRGB plus SHO in one wheel | LRGB only, or SHO plus one or two extras, with less weight |
See all filter wheels and drawers.
What's in the box
- EFW 7x2" filter wheel
- USB 2.0 Type-A to USB-C cables, 0.5m and 2m
- M54M-M48F, M54M-M42F and M54M-M48F-2 adapters
- Bag of 10 filter masks
- M2.5 × 6 screws (6) and M2 × 4 screws (26)
- 3 × 75mm Phillips screwdriver
Filters and the camera are sold separately.
ZWO EFW 7x2" FAQ
Do I need a filter wheel?
With a mono camera, yes, to shoot color. A filter wheel changes filters automatically during the night. With a color camera you usually don't; a single dual-band filter in a filter drawer is enough.
2-inch or 1.25-inch filters?
For APS-C and full-frame sensors, choose 2-inch (or 36mm for APS-C) to avoid dark corners. 1.25-inch filters suit smaller sensors like the ASI533MM.
7 or 5 positions?
Seven fits LRGB and SHO with no compromises. Five is enough for LRGB plus one narrowband filter, or for SHO with luminance and one spare.
Does it need its own power supply?
No. It runs on 5V USB power, typically from the hub on a ZWO cooled camera, so only one short cable goes to the wheel.
Will it work with my software?
Yes. It works with ASIAIR, ASIStudio and any ASCOM program such as N.I.N.A., and it's plug-and-play with no driver to install.
What's new in the 2025 model?
A USB-C port replaces the old USB Type-B, the chassis and motor are sealed against light leaks, and the body has a refined laser-engraved finish.
Specifications
| Filters | |
|---|---|
| Positions | 7 |
| Supported filters | 2" mounted (filter area ≤7mm thick) or Ø50mm unmounted (1.5–3.5mm thick) |
| Carousel | 6061 aluminum, M48 × 0.75 cells |
| Optical and mechanical | |
| Optical thickness | 20mm |
| Threads | M54 × 0.75 (adapters to M48 and M42 included) |
| Body | CNC-machined aluminum, about 199mm wheel diameter, 209.5mm tall |
| Weight | 720g (1.6lb) |
| Electronics | |
| Connection | USB-C (USB 2.0) |
| Power | 5V, 120mA from USB |
| Software | ASIAIR, ASIStudio, ASCOM, ZWO SDK; no driver needed |
| Model / SKU | ZWO-EFW-7x2-25 |