ZWO EFWmini (5 x 1.25″or 5 x 31mm)


SKU: ZWO-EFW-MINI Category: Tag:

Product Description

The smallest and most lightweight 1.25″ Electronic Filter Wheel in the world!

300g  ONLY ! Small than your hand !

EFW in Hand

The body is CNC machined from a full block of aircraft grade aluminium.

Very thin design, 20mm ONLY



EFW in Hand side view

The step motor is the heart of the EFWmini, which is made by NPM from Japan. You can trust its quality and relability.


Supports both 5*1.25″ filters or 5*31mm filters

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


Only one USB Cable is enough to power up the EFW, the max power consumption is around 120ma@5V, so you can connected it form the USB2.0 hub of our cooled cameras.


The distance between the filter and sensor is aroucnd 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 vigentting up to F2 lens

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


The full EFW mini Set includes:

EFW mini body, T2 nosepiece, 1.25″ Holder-T2, T2-T2, USB2.0 Cable

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

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

EFW kit -

Mechanical drawing:


How to use it?

you juse need to plugin the EFW mini 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 EFWmini in one software.


  • 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. :

    What software can be used to control the EFW?



    • Sam Wen


      there is ASCOM driver for the EFW
      so any software support ASCOM EFW can control it
      such like SGP MDL APT…

  2. :

    This looks great! It says that it will only work on scopes up to f5 without vignetting. Does this mean there will be vignetting on f4 newtonian as well? Also, I have a refractor that is f.5.5, but with the reducer it is f4.3. Will this setup vignette? (I’m interested in using this with the 1600MM camera. Thank you!

    • Sam Wen


      yes,I think there is very small vignetting for F4 scope, but should be not very noticeable

  3. :

    Looking at the picture of the ASI1600mm-c associated with the EFWMini, the output seems to have been changed from a guide port to a USB 2.0(see picture in the camera URL). I am expecting a delivery of a ASI1600mm-c in the next few days and wonder how to run a EFWMini if the camera I get has the guide port only?

    • Sam Wen


      all cooled cameras we are producing are with USB Hub
      you can also connect the EFW with a usb2.0 cable directly to your computer

  4. :

    An automatic filter wheel is awesome! Will it work with The Sky X so I can control it remotely on my Paramount?

    • Sam Wen


      of course, ASCOM driver is supported
      all software compatible with ASCOM will work

  5. (verified owner):

    What diameter and thread count are the retaining screw holes for the 31mm filters? I believe that a competitor’s similar screw is size 2/56.

    • Sam Wen


      yes, they are M2

  6. :

    Whether there will be a version with 7 or 9 filters?


    • Sam Wen


      I think big one will take around 2-3 months

  7. :

    Hi my scope is f5 + reducer which bring it down to f3.6.
    If I use 31mm with this wheel will it still have vignett?


    • Sam Wen


      no vignetting if you use 31mm filter

  8. :

    Hi Sam.

    Do you have any schedule for develope the EFW for 2″ unmout filters.
    If you have, when?


    • Sam Wen


      we don’t have such big camera
      so I think our big EFW will support 8*1.25 7*36 at first
      do you think T2 is big enough for 2″ filters?

  9. :

    I have 2″ LRGB unmount filters.
    That’s why I said so.

    • Sam Wen


      OK, our big EFW will choose to use T2 interface on both sides

  10. :

    What height filters can be used with this filter wheel? I have a set of Baader LRGB filters already – overall height, including threads is 9.5mm

    • Sam Wen


      the threads can accept 3mm and the height of the filter without threads can accept 7mm

  11. :

    hi sam,
    I’ve tested your efw, it works fine.
    I think the ascom driver could be better if the user could rename filters.
    Is it expected?


    • Sam Wen


      thanks for the suggestion, can you show us example?
      you can email us

  12. :

    What is the total backfocus of the EFW and ASI1600MM-cool?


    • Sam Wen



  13. (verified owner):

    Bonjour, Avez vous le lien des pilotes pour la roue à fitre, ça ne fonctionne pas.
    Quel “port COM” faut-il utiliser car j’ai tout essayer???

    • Sam Wen


      There is no COM port and it don’t need driver
      it’s a HID device just like keyboard or mouse
      you just need to install our ASCOM driver to use it

  14. :

    Will there be an option of purchasing additional carousels for this filter wheel?

    • Sam Wen


      do you mean the filter wheel?

  15. :

    Hi Sam!
    I have ASI 1600MM-Cool, the Sky-Watcher 80ED and SW 0.85x reducer telescope. I want to buy ZWO EFWmini, but I don’t know what to provide a rabody segment of SW 0.85x reducer. You can help?

    • Sam Wen


      the reducer usually require 55mm back focus
      so you can connect the the camera to your scope like this
      1600 + EFWmini + T2-T2 + T2 extender + T2-M48
      this distance should be very close to what you need

  16. :

    When the order for aliexpress is available?

    • Sam Wen


      we will try to upload in next few days

  17. :

    Looks like a great product!
    Are there buttons on the unit to move the filter wheel manually, or can you only switch filters with a computer attached?

    • Sam Wen


      this is controled by computer

  18. :

    What is the length of the USB cable? I bought a ASI178MM from OPT but it does not have a USB hub. This camera has a guide port. :(

    I am starting to think I should have ordered one direct from you with a USB hub. Then the cord length would not matter.

    I’m also concerned that if the cable is too short, I may need to buy one that is longer. What kind of ends does the cable have? Obviously one end is USB, what type of end plugs into the EFW?

    • Sam Wen


      the cable come with the EFW is 2 meters
      the new camera with hub has 2 short cable 30cm

  19. :

    Any plans for indi driver?

    • Sam Wen


      there is already one test version

  20. :

    A really great product but the washers supplied with the M2 screws used to retain 31mm filters are too small in diameter to hold the filters.
    I have ordered slightly larger ones which hopefully will secure my Chroma 31mm filters.

    • Sam Wen


      thanks for the suggestion
      we already changed the washers to bigger one

    • Sam Wen


      thanks for the suggestion, we already changed the washers to bigger one

  21. :

    Whenever I try to connect via MaximDL I get the following error:
    “Error initializing camera or filter wheel
    Error opening filter wheel
    Unable to initialize filter wheel”

    I’m on Windows 10 and have uninstalled and reinstalled 3 different versions of the ascom driver


    • Sam Wen


      did you install our EFW ASCOM driver?
      we need more detail of your problem
      I will send you one email

  22. :

    I would like to directly communicate with the filter wheel, do you have a document or header file with the HID command set?

    • Sam Wen


      there is SDK to control our EFW but no command

  23. :

    Hi Sam,

    I have a Stellarvue SV70-T and it has a threaded focuser which I will be using their Focal Reducer/Flattener. Will I be able to get a solid connection all the way through your EFW Mini to the ASI 1600mm to maintain a rigid alignment? The FR/FF needs 55mm back focus?

    • Sam Wen


      yes, I think it won’t have problem
      you can add the OAG as extender 😉

  24. :

    Dear Sam,

    would it be possible to equip the EFW mini with 36mm unmounted filters? I’m thinking of a new wheel with only 4 positions then. Would be perfect for your new tricolor NB set plus clear glass for focussing / luminance!

    • Sam Wen


      we will check if it compatible with 36mm 4 position

  25. :

    Hello Sam,

    I have a Stellarvue SV70T with FR/FF and will be ordering a 1600mm-cool and the EFW mini with 31mm filters. I’m also considering the ZWO OAG. The Stellarvue FR/FF requires 55mm backfocus. So I will have the 1600 + EFWmini + T2-T2 + T2 extender + OAG

    6.5+20+1+11+16.5 = 54.5mm.. Close enough. Is this correct??

    Also..The SV70T with the FR/FF is F/4.8 336mm. Is the 1600 the best choice, of the ZWO cameras, for a wide field scope like the SV70T?


    • Sam Wen


      yes, just the T2-T2 is 2mm thickness
      1600 is very suitable for SV70T

  26. :

    I’m trying to interface to the EFW through labview, using the DLLs that you provide. However there is no documentation about the function prototypes. I need a .h file, or else a simple list of the function prototypes, or else I’m stuck.

    • Sam Wen


      yes, just download from our software page under SDK section

  27. (verified owner):

    Hi Sam,
    I recently purchased the EFW and need to some help with the backfocus on my EdgeHD11. With the C11 backfocus being 146mm I have the .7X reducer, standard celestron T-adapter (if needed), EFW, ASI290MM. What kind of additional spacing would be required for this imaging train?

  28. :

    Good evening,

    I recently purchased the EFWmini and I download “ZWO EFW ASCOM Setup V1.0.0.6” ASCOM driver, but this driver is not able to install. There is below the error message :

    “The ASCOM Driverhelper object has failet to load, this indicate a serious problem with the ASCOM installation”
    “The ASCOM Utilities object has failet to load, this indicates that the ASCOM Platform has not been installed correctly”
    “The ASCOM Platform 6.0 or greater required for this driver.”

    Did you change something on that driver because I’m unable to use the EFWmini with that problem?


    • Sam Wen


      you need to install ASCOM Platform at first

  29. :

    Hi Sam,

    I have bought ZWO ASI120MC for autoguiding and occasional planetary imaging. Since I am planing to start Deep Sky imaging, I also bought ZWO OAG, too.
    Now I am intending to buy ZWO ASI1600 MM-Cooled and ZWO motorized filter wheel for 5 1.25″ filters with filter set.

    My questions is what type of adaptors should I buy additionally in order to connect the OAG (with 120mc on it) to the Meade LX90 rear opening (that is a male-type 2″ thread), than the filter wheel and finally, the 1600mm-c camera, in that order?
    SInce I am purchasing all that items in neighbor country, I must plan the orders in advance.

    Thanks in advance,

    • Sean Wang


      There is a M48 adapter come with OAG, It will help you connect the telescope. And EFW have T2-T2 ring help you connect the OAG and EFW.

  30. :

    Thanks Sean, but the visual back (rear cell) opening of LX90 is 2″ wide.

    • Sam Wen


      you can get one 2″-1.25″ adapter

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