ZWO EFW 8 Position Electronic Filter Wheel for 1.25 and 31mm Filters


  • €479,95
    Unit price per 
Tax included.
Will be in stock after

ZWO EFW 8 Position Electronic Filterwheel for 1.25 and 31mm Filters

This ZWO EFW 8 Position Electronic Filterwheel for 1.25 and 31mm Filters is most likely one of the smallest 8-position filter wheels in the world. It is also extremely lightweight, it weighs 400g only.

Its housing is CNC machined from aircraft grade aluminium alloy.

The stepper motor, that is the heart of any electronic filter wheel, is made by a reliable Japanese company, NPM. You can trust its quality and reliability.

This high quality 8-position filter wheel has been designed mainly for astro photography, especially, but not exclusively for ZWO ASI1600 cameras.

Depending on the focal ratio of your telescope you can use it with standard 1.25" filters in filter cell or you can choose 31mm unmounted filters where a smaller filter would cause vignetting and use of at least 31mm filters is necessary.

As it is ASCOM compatible, therefore it can be used with cameras of other brands as well.

Up to 8 filters can be installed in the numbered compartments that accepts both 1.25" (mounted) and 31mm (unmounted) filters (or semi-mounted 31mm Astronomik filters), and each can be selected for your eyepiece or camera from an imaging software.

 ZWO now offers 1.25", 31mm and 36mm LRGB and narrowband deep sky filters as well.

The ZWO EFW 8 Position Electrobic Filterwheel for 1.25 and 31mm Filters can be attached to your focuser either by the supplied 1.25” nosepiece adaptor or via a T-thread. There is actually a female T-thread on both sides of the filter wheel, but it also comes with a reverse adapter with male T-thread on both sides.

The robustly constructed filter wheel is supplied with a 1.25” nosepiece and a 1.25” eyepiece holder with brass compression ring.


The full ZWO EFW 8 Position Electrobic Filterwheel for 1.25 and 31mm Filters set includes:

  • EFW 8-position filter wheel
  • T2 nosepiece
  • 1.25″ Holder-T2
  • T2-T2 adapter
  • USB2.0 Cable

Please note: your focuser will require 20mm of additional inward focusing distance from the normal focus position to compensate for the thickness of the filter wheel.

This filter wheel will be a good addition to the new ASI1600MM Pro camera, (please make sure that your telescope otherwise have enough back focus, of course, e.g. Newtonian telescopes would usually have a back focus issue, unless modified or specially designed for astro photograpy...)


LIMITING F-RATIO, for ASI1600 Owners

The distance between the filter and sensor is around 10mm when you connect the ASI1600 to this EFW8, so a 1.25″ filter won’t have vignetting with a scope with up to about  f/8-f/9.5 focal ratio (depending on the thickness of the filter) and a 31mm filter won’t have vignetting up to about  f/2.8-f/3.2 lens (depending on the thickness of the filter). Please note, these figures are slightly different from ZWO's own calculations and to be checked in practice.


Notes for non ZWO Filters

1.25″ filter requirement: threads length shorter than 3mm, height without threads less than 7mm

31mm filter requirement: a set of M2 screws and washers needed to fix the filter are included in the package


How to use it?

you just need to plugin the EFW with a USB2.0 cable and install the  ASCOM driver from here.

There are  ZWO Filter Wheel(1) and ZWO Filter Wheel(2) to select,  you can use either one of them.

You can control 2 filter wheels simultaneously from one software.


  • Limiting F-ratio: appr f/3 with 31mm filters and f/8 with 1.25" filters (calculated with ZWO's 2mm thick filters)
  • Thickness: 20mm
  • Power consumption: 150 mA at 5 Volts
  • ASCOM compatible
  • Positions: 8 x 1.25" mounted, or 8 x 31mm glass, unmounted or semi-mounted (like Astronomik)
  • Weight: 400g

We Also Recommend