ZWO EFW (8 x 1.25″/31mm or 7 x 36mm)



Product Description

Our latest EFW (Electronic Filter Wheel), larger than the previous but still low on weight. Only 400 grams (14 oz)!


The body is CNC milled from an aircraft graded aluminum block.
We decided to make it thinner, where it measures only 20 mm on the wheel body.


The heart of our EFW comes from NPM, Japan, whose the manufactor for the stepmotor and the quality is trustful and reliable. Guaranteed long life.


We have two specifications:

TYPE1: 8 positions, 1.25″ or 31mm filter can be used.

TYPE2: 7 positions, 36mm filter can be used.

The Electronic Filter wheel can be rotated in both counter clockwise or clockwise direction for filter selection.



There are no need for multiple cables to power this wheel up, just one USB cable does the trick.The power consumption of this EFW is approximately 120mAh @ 5V, which can be operated from the Cooled CCD’s USB hub.


The distance between the filter and sensor is around 10mm when you connect it to ASI1600.

So 1.25″ filters won’t have vignetting up to F5 focal ratio scope and 31mm filter won’t have vignetting up to F2 lens.

Our new RGBL filters are recommended to work with ASI1600, it will offer nearly 1:1:1 RGB color balance.


What`s in the box?

  1. 8*31mm or 7*36mm EFW body
  2. 1.25″ Holder-T2
  3. T2 nosepiece
  4. Phillips screwdriver
  5. A bag of M2 screws
  6. T2-T2 adapter(male)
  7. USB2.0 cable



How to install the filter?

1.25″ filters required to be: threaded  shorter than 3mm in length,  without threads less than 7mm in height

  1. Take the back cover off
  2. Lay the wheel down flat
  3. Screw-in the filters up
  4. Put the back cover on

Take the EFWmini for an example:


31mm and 36mm filter requires: a set of M2 screws and washers needed to fix the filters are included in the package .

  1. Take the back cover off. Lay the wheel down flat
  2. Hold the filter by the very edges and lay them in to the recess for each position
  3. Attach the washers,put in the screws
  4. Put the back cover on

Take the EFWmini for an example:


How to connect with the camera and telescope?


How to use it?

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

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

There are 2 ASCOM is for controling 2 EFW in one software.

Mechanical drawing



  • Fast Shipping(amount ≧ 299USD) for free
  • Fast Shipping(amount < 299USD) : $20.00
  • Free Shipping(amount < 299USD) (Air Mail, 3-4 weeks) (Free)


  1. Fast Shipping: we will choose DHL, UPS, TNT, EMS etc to deliver it. Usually you will get your package in one week. We provide free fast shipping for order ≧ $299 or charge extra $20 for order < $299.
  2. Free Shipping: we will ship via DGM or China Post Registered Air Mail. It usually costs 2-3 weeks to reach US or Europe and costs 3-4 weeks to reach far places.
  3. Customers from Brazil and Chile should leave a message to provide your CPF or CNPJ as your custom needs it.
  4. Customers from Russia need to provide the name of your company.

Tracking site:


China air mail:


  • The price list on our website is USD without tax.
  • Please note that buyers areliable to pay tax involved, such as Import tax, VAT , customs handling fee, etc. The additional fees may be collected at time of delivery by courier.
  • For best local service we advise customers buy our cameras form local dealers.

Warranty and Return Policy

  • We provide 2-year warranty for our products, we will offer the repair service for free or replace for free if the camera doesn’t work within warranty period. After the warranty period, we will continue to provide repair support and service on a charged basis.
  • This warranty does not apply to damage that occurred as a result of abuse or misuse, or caused by a fall or any other transportation failures after purchase.
  • Customer must pay for shipping when shipping the camera back for repair or replacement
  • If you get a faulty camera, please contact us as soon as possible though email: Please describe the problem in detail and we will do our best to help you solve the problem. Most instances perceived problems are simply bad driver install or software configuration.
  • For customers who bought the camera from our dealer, dealer is responsible for the customer service for you.

Do you have uestion, answer or comment? Post here!

  1. :

    Will you sell an EFW+OAG package soon?

    • Sam Wen


      OAG will be ready at this month

  2. :

    Will this be offered in a kit? I am interested in the ASI1600MM-cool kit but would like this EFW instead of the EFWmini.

    • Sam Wen


      yes, the kit will come

  3. :

    Will the filter carousel be available separately? If I purchase the 8×1.25″ version as a started, is it possible to purchase only the carousel if I should upgrade to 36mm filters?

    • Sam Wen


      of course, the 36mm filter will be provide separately

  4. :

    Looks very interested.
    1. How thick will this new Filter wheel be?
    2. How much back focus will it take up?
    3. Will there be an ASCOM driver available when it is released?
    4. T-Threads front male? back female?

    • Sam Wen


      1. still 20mm
      2. 20mm
      3. yes, the same one with EFWmini
      4. yes, T2 in both side

  5. :

    Whether the order for aliexpress will be available?

    • Sam Wen


      need to wait to next year, there is some problem with aliexpress platform

  6. :

    Will the zwo EOS adapter for mini EFW work with this new filter wheel as well?

    • Sam Wen



  7. :

    Can you give us the dimensions? How thick is it? I am concerned about my total back focus.

    Are you currently developing an OAG to pair with the FW and 1600? If so, is there a time frame for release?


    • Sam Wen


      20mm thick, our OAG will pair with EFW and 1600 and in 55mm back focus distance

  8. :


    Thanks for the response. Really curious to when the OAG will start shipping? I am eager to buy all three OAG/FW/1600. but can’t buy any until they are all available for sale!

    Thanks again,

    • Sam Wen


      I am sure our OAG will be available in end of this month

  9. :

    What is the thickest filter cell this FW will accept (not counting the threaded length)?

  10. :

    Sorry, I missed the information in the description. So it seems like some older Astrodon filters may not fit into these filter wheels due to there excessive height (my Astrodon 6nm Ha measures 8mm thick without thread).

    • Sam Wen


      that’s bad news

  11. (verified owner):

    How thick will be the new OAG?

    • Sam Wen



  12. :

    This product is already available to purchase?

    • Sam Wen


      yes, it’s instock

  13. (verified owner):

    Thickness of EFWmini and EFW 8 x 1.25 identical?

    • Sam Wen


      yes, 20mm

  14. :

    The thickness is reported, but what is the height and width (e.g. The diameter of the wheel) of the EFW (NOT the Mini). Also will it accommodate 7 x 36mm unmounted Astrodon filters which are thicker than most?

    • Sam Wen


      we will upload the diameters soon, you can use unmounted filters
      we use screw to fix their position

  15. :

    Is there going to be 2″ version any time soon?

    • Sam Wen


      I don’t think very soon
      but we will release when there is new ASI camera need 2″ filters

  16. :

    The description says the 1.25″ filter won’t have vignetting to f/5 and 31mm won’t have vignetting to f/2. Since 1.25″ = 31.75mm I am wondering if this is a typo error? Perhaps it should have said 36mm won’t have vignetting to f/2. Is this a correct assumption?

    • Sam Wen


      this is the vignetting working with our ASI1600 cameras

  17. :

    Sam, You may disregard my question above. I have since learned that a 1.25″ filter is actually only 28mm diameter of usable filter (not simply a conversion from inches to mm), so that explains my confusion.

    • Sam Wen


      usually 26mm diameter actually
      31mm filter have 28mm diameter usable filter

  18. :

    I already have LRVBHaO3S2 astrodon filter in 36mm.Do they be ok with the EFM 7position ? When the OAG will be aviable ? you say befor it arrivend curent novebre 2016 ?? Also the package OAG/FW/1600MMC ? Sicnerly.

  19. :

    Will this filter wheel work with a Mac OS program like Nebulosity?

  20. :

    Is it possible to operate the EFW (8×1,25″) without the cover (filters exposed)?

    • Sean Wang


      I don’t think so, without cover, how could we attach?

    • Sam Wen


      you can operate the EFW without cover at night
      I am afraid it may have problem under very bright light

  21. :

    Also is it possible to get a 3D-model of the EFW 8×1,25″ (e.g. STEP-file)?

    • Sean Wang


      we only have 2D draw in product description.

    • Sam Wen


      sorry we didnot provide it

  22. :

    What is the thickness of the filter wheel (7x36mm)?

    • Sam Wen



  23. :

    What is the thickness of the carousel in filter wheel (7x36mm)?

    • Sam Wen



  24. :

    Thanks for the replies!

    We are not intending to use it between telescope and a camera, but this will be the first device in the system, therefore we do not need the wheel cover for attaching anything, we only mount the EFW to the system. 😉
    Thanks for the note about bright light, good to keep in mind if we have problems.

    • Sam Wen


      that’s good, because we used IR light sensor to check the position

  25. :

    What are the dimensions of this filter wheel? Would it block too much light when used on my 11: EdgeHD with Hyperstar?

  26. :

    Hi! What’s the orientation of the ASI1600 sensor once screwed to the filter wheel? Would it be horizontal or some random angle?

    Thanks and clear skies!

    • Sam Wen


      yes, there is T2 spacer come with 1600, so you can adjust this angle by using the thin spacers

  27. :

    Do you have an estimate for introduction of an integrated EFW and OAG?

    • Sean Wang


      To be honest, we didn’t have that plan. But it’s a good idea. Maybe in the further we will consider to make one.

  28. :

    Do you have any driver for operating it with a Linux Machine? I’m using your cameras with the ASICamera2 SDK, but it doesn’t say anything about a FilterWheel. Thanks in advance

  29. :

    When using 1.25 on F/4 vignetting will be very strong? The flat field won’t help?

    • Sam Wen


      it’s not very strong, but you can notice it after strech

  30. :

    Sam, thanks!
    I badly understand English. I badly understood the answer to my question. Answer more simply.

    • Sam Wen


      I mean vignetting is very small and you can use it

  31. :


  32. :

    Hi Sam

    Do your Sony IMX128 full-frame sensor (36 mm x 24 mm) camera need 2″ filters and will you be making a
    2″ version any time soon ?

    • Sam Wen


      this is color camera, you don’t need filter wheel
      2″ filter can be used with ASI128

  33. :

    Hi Sam:

    Is the IR position led isolated to avoid any light leakage entering into the CMOS camera sensor?

    • Sean Wang


      In my experience, Yes. won’t be a problem.

  34. :

    Will mounted 31mm filters such as Astrodon Tru Balance E-series fit? I notice the 31mm filter sold as part of the kit are unmounted. Thanks!

    • Sean Wang


      Yes, I think so. it have same diameter as ours.

  35. :

    I am interested in getting a set of Astrodon 36mm NB filters and I emailed Don Goldman to find out the filter size. He advised that his filters are 36.1mm diameter and 3mm thick. Will these be compatible with your filter wheel?

    • Sean Wang


      Hi bob. Our 36mm position diameter is 36.1mm. I think it is suitable, but never tested. Thickness is OK. Maybe you can ask this in cloudynight, somebody might do this before.

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