SKU: ZWO-OAG Category:

Product Description

ZWO Off-Axis Guider for astronomy photograpy


1.Lightweight, 16.5mm thickness
2.large prism:8*8mm
3.Connect the main imaging camera and the guide camera. No guide scope required!
4.Flexible adaption to your camera and telescope  , such as  M42 and M48.
5.Fully compatible with all ZWO ASI cameras
6.Good stability , strong connection to the telescope

ZWO OAG comes with all adapters you will need for imaging and guiding.

Package includes:


1.       1.25holder for 1.25″ size body guide camera

2.       5mm T2 extender for ASI guide camera whose back focus distance is 12.5mm such as  ASI120, ASI224MC, ASI290 etc..

3.       M42 adapter for main imaging camera

4.       M48 adapter for main imaging camera

5.       OAG body with M48 telescope adapter

6.       M42 adapter for telescope

Mechanical Draw


Usage Guider:

1.   please caculate the correct required distance for your imaging train at first

for example: you need to attach 21mm extender to ASI071 to reach 55mm back focus distance:17.5mm+21mm+16.5mm=55mm


2. Take off the guider prism part and attach OAG body to the telescope


3. Insert the prism part into the OAG body


4.  Mount the guide camera


5.   Screw the T2 or M48 adaper on the imaging camera according to your the mount type


6. Mount the camera on the OAG in correct position and lock the 3 screws


7. The final setup


Note: please make sure the prism won’t block the imaging area


Use the guiding screw to adjust the guiding camera’s focus.

You’d better do it at day time to make sure imaging camera and guiding camera can reach focus at the same position.



Before first usage of this product read manuals and install correct drivers and 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. :

    How fits the big filter wheel? how to choose the position of the wheel to give free space to the guide camera?

    • Sam Wen


      the only available position is upside of the EFW
      there is around 30 degree angle to adjust the OAG

  2. :

    Will you offer a new KIT with the OAG?

    • Sam Wen


      you can order the OAG separately as there is already too many kits;)

  3. :

    That’s true. Thanks Sam :)

  4. (verified owner):

    If I’m using the OAG with a ASI1600MM-C as the main camera and a ASI 290MM as a guide camera, do I need the M42-M42 extender (21mm length) to get the two cameras in the same focal plane?

    • Sam Wen


      yes, the OAG cannot be too close to the main camera
      you need the extender to reach focus

  5. (verified owner):

    How does the guide screw focus adjustment work? Does turning the screw in and out adjust the focus? Or is it a locking screw to hold the guide camera in place once you manually raise or lower the guide camera? I hope it’s the former.

    • Sam Wen


      the camera will rotate when you adjust the focus

  6. :

    I have and ASI 1600 MM Cooled with the Electronic filter wheel. To have this properly space I would need a 12mm spacer to go between the OAG and the filter wheel. (55mm – 6.5mm – 20mm – 16.5mm = 12) It looks like you are offering a 21mm spacer for your color cameras, but will you be offering a 12mm spacer for customers who have Monochrome camera setups like mine?

    • Sam Wen


      1600 come with one 11mm extender and there is one T2-T2 adapter come with EFW
      total back focus can reach 56mm

  7. :

    @Jonathan, I think this will work. ASI1600MM-C+EFWmini+T2 to T2 (from EFWmini kit)+11mm T2 ring (from ASI1600 kit)+AOG+T2 extender 18.5mm (from ASI1600 kit) will give you the correct setup.

    I havent measured it but I think the T2 to T2+11mm T2 ring will give you your 12mm.

  8. (verified owner):

    The screws to hold the telescope adapter are too short (4mm). They only provide about 1 thread engagement for each of the 4 screws. They should be at lest 6mm or possibly 8mm long. I wouldn’t trust hanging $2000 worth of cameras & accessories off these fasteners. Good luck finding longer replacements at your local hardware store. These are specialty screws with a small head (4mm) and shoulder (1.3mm). Standard M4 x .7 screw heads are 7.5-8.0mm in diameter and have a longer shoulder (2.3mm). Using standards M4 x .7 flat head screws won’t sit flush with the telescope adapter causing conflicts when threading on the back of the telescope. ZWO needs to ship longer screws for the telescope adapter.

    • Sam Wen


      sorry for this issue, usually 4 screws is tight enough to hold the camera
      anyway we will check and replace with longer screws

  9. (verified owner):

    Thanks Sam. I still haven’t been able to find a source for longer screws. If you have lsome maybe you could drop 4 in the (slow) mail for me.

    • Sam Wen


      OK, please email our customer service info mail

  10. (verified owner):

    Hi Sam,

    I have your new OAG and plan to use your ASI 224 for auto-guiding and have a couple questions.

    With your OAG will I have trouble finding a suitable guide star at 2800mm on my Celestron 11″ Edge (@ f10)? How large a sensor can your OAG use? It seems the opening from the small mirror up to the camera is very small so a larger sensor would definitely be cropped. I assume the ASI 224 is ok and not cropped!

    I wish I could move the mirror sideways a bit to acquire a star to guide on, as the field of view is really tiny, especially at 2800mm F/L

    How high would you suggest I set the gain on the ASI 224 with OAG? Should I forget using the OAG with my C11 and just stay with my wide field refractor only?


    • Sam Wen


      you can use up to 1″ sensor for the OAG
      I would recommend a mono camera for guiding instead of color
      so maybe ASI290MM is better
      you can set the gain to around 400 for 224

  11. :

    I’m wondering what the ACTUAL sensor coverage is with this OAG.
    I will definitely order one, over the other similar clones, if the prism tower does not severely restrict the specified SQUARE 8x8mm pickup prism size.
    From one of the pictures it looks like this one also has a CIRCULAR light path just short of 8mm diameter.
    I know that making a round hole is easier(!), but I would pay more to lessen the rather severe obstruction.
    Thanks :)

    • Sam Wen


      the hole is 6mm*6mm which is suitable for most sensor
      even 1″ sensor may only suffer from vignetting problem

  12. :

    Dear Mr. Sam,

    I am using my ASI1600MM-C with my ES ED 80 refractor and ES field flattener. The field flattener’s recommended back focus distance is just 45mm. My guide camera is ASI120MM. Can I achieve a good focus in the guide camera with this OAG? (I failed to do so with my Orion thin OAG).

    Thank you.

    • Sam Wen


      yes, you can

  13. (verified owner):

    How long is exactly the thread on the “M48 adapter for main imaging camera”?

    • Sam Wen


      It’s around 4.5mm length

  14. (verified owner):


    I would like to buy a M42 adapter for my OAG, my current one is totally destroyed, it got bent with me making the screws tight. How can I buy a new one? Thanks!

    • Sam Wen


      we will reply you in email

  15. :

    Sam Wen – December 27, 2016:
    the camera will rotate when you adjust the focus

    What do you mean? I just purchased the OAG and nothing rotates. How is focus obtained?

  16. (verified owner):

    Hi Sam, can the tilt angle of the prism be adjusted on the OAG? I noticed there is a little grub screw holding the prism to the stalk, but I have not yet been brave enough to attempt any adjustment of it.

    Currently I’m using a asi1600mm-c with efw-mini​and explore scientific coma corrector. I have the prism perpendicular to the sensors long edge and right on the very edge of the light column to minimise sensor shading & light reflections. My guide cameras image is quite dark compared to my 60mm F4 guidescope, although binning 2×2 helps.

    But the real problem is that despite my asi1600 having sufficiently round stars out to the corners of the frame, my guider’s stars look more like eyebrows. I assume that is a combination of vignetting and coma, so hopefully it can be tilted slightly closer to the better corrected middle of the light column.


    • Sam Wen


      usually there is no need to adjust the angle of the prism and I don’t think tilt can help to correct coma
      I think one thing important is you need to try to put the prism close to the sensor(upside or downside of the sensor)

  17. :

    When it is available to the order for AliExpress?
    It is inconvenient to me to pay through PayPal

    • Sam Wen


      we will upload soon

  18. (verified owner):

    I managed to adjust the angle of the prism just a tiny bit closer towards the centre of the coma corrector (it was angled slightly out from centre rather than parallel with the main camera) and I now get a much better image that completely fills the guidecam sensor, is brighter and has much closer to round stars. Thanks

  19. (verified owner):

    It would be good if you guys could make a low profile, non-rotating helical focuser for use with this OAG. Baader have one that looks like it could work, but I reckon you guys could make one a good bit cheaper 😁

    • Sam Wen


      thanks for the hint, we will try

  20. :

    Is there any configuration that could allow this OAG to be used with a Canon EF lens? I do quite a bit of imaging with a 400mm f2.8 lens, ASI 1600MM-C, and EFW filter wheel. I’m really hoping to go OAG with this setup.

    • Sean Wang


      I think it is hard to used in canon lens. because the last glass of lens is small, OAG can not get any light form the lens.

  21. :

    Hello there, I have read in several thread (CN, Astronomy forum, even here in your support forum) about wobbling problems of the prisma stack. The following video shows the problem:

    Have this issue been properly addressed? I am really interested in ordering this OAG however, I have my doubts considering the problem faced by other users. Any comment/feedback would be highly appreciated.

    Clear skies, Diego

    • Sam Wen


      we already added 2 screws to fix the OAG prism, so won’t have such problem again

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