SKU: ZWO OAG Category:

Product Description

ZWO Off-Axis Guider for Astrophotography

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 and rigid connection to the telescope to minimize flexing of the imaging train

1 2 3OAG连接相机-正视图

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


Package includes:


1.       OAG body(with 1.25″ holder and 5mm extender and M42 adapter)

2.       M48 adapter for main imaging camera(in the box)

3.       M48-M42 adapter for telescope and flat lens(in the box)

4.       Hexagon wrench and Spacer(in the box)

Mechanical Diagram

Mechanical Diagram

Connecting Diagram:


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 mount type.


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


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.



Our website is continuously updated with the most recent camera drivers as well as software for DSO and planetary imaging. Please make sure the most recent Driver and software have been installed before you start shooting:

It is also recommended to read the Manuals first before shooting.

Shipping & Delivery

Fast Shipping: we will choose DHL, UPS, FedEx etc to deliver it. Usually you will get your package within 15-20 days.

  • Fast Shipping(amount ≧ 199USD) for free
  • Fast Shipping(amount < 199USD) : $30.00 (We do not provide free shipping from now on.)


  1. It will take around 60-90 days for shipment via ePacket/China Post Registered Air Mail/EMS, which can’t be guaranteed due to force majeure. If you can’t get the air mail package after 2months, please let us know ASAP:
  2. Customers from Brazil and Chile should leave a message to provide your CPF or CNPJ as your custom needs it.
  3. Customers from Russia need to provide the complete English name with three words as well as the English shipping address.

Tracking site


China air mail:



  • The price list on our website is USD without tax.
  • Please note that buyers are liable 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 from local dealers.


Warranty & Return

1. ZWO hereby declares that it will provide customers with a warranty period of 2 years for ZWO branded products (excluding APO), as per this policy. APO products will be covered by a 1-year free warranty service, starting from the day following the receipt of the product by the customer. For ASIAIR Plus users, the warranty period will commence from the day of device activation.

2. If a User encounters the following Dead on Arrival (DOA) and contacts ZWO within the corresponding time limit to issue the Product purchase invoice and relevant evidence, ZWO will provide door-to-door pick-up service and, as appropriate, after-sale replacement (or partial replacement), repair or return (or partial return) service for the following Products:
1) Product quality problem
Provided that a User detects a quality problem and contacts ZWO within 30 days after receipt of the Products, and ZWO support team confirms that the Products indeed have a quality problem or defect after their inspection, ZWO will provide free replacement service towards such Products;
2) Product transportation problem
Provided that a User finds obvious signs of bubbling, serious overstocking, or deformation on the outer package of the Products upon receipt of the Products, and provides ZWO with pictures of the outer package and proof of receipt within 3 days after receipt of such Products, ZWO support team will verify the actual shipper and determine the responsible party for such transportation problem. In the event that ZWO is the actual shipper, ZWO will be responsible for providing the relevant return or replacement service, however, if the Products are directly sold or transported to the User by an agent of ZWO, the agent will be responsible for providing the relevant return or replacement service.

3. If the Products are under the following circumstances, they are not within the scope of warranty service, ZWO may provide maintenance services to the Users:
1) The Warranty Period of the Products has expired; or
2) The Products are injected into liquid or affected by moisture or corrosion; or
3) The Products are damaged by an external force (such as the broken of the camera protection window glass, the deformation of the product shell, the broken of the USB port, etc.); or
4) Disassembling, repairing by a third party, refurbishment of the Products (such as downloading erroneous firmware) without the written authorization of ZWO; or
5) The product system is modified, or the maintenance notice is lost or changed; or
6) Product quality problem caused by installation not following the requirements or instructions for the Products; or
7) Physical damage or failure of the Products caused by the force majeure (such as strong vibration or extrusion such as flood, fire, earthquake, or thunder stroke); or
8)Damage caused by the improper User operation during the period of shooting or use, such as using without the equipment protection or direct shooting of the sun; or
9) No valid purchase invoice or warranty certificate; or
10) The Products are second-hand products.
Any quality problem with the accessories or other parts of the Products is not a condition for the return or change of the Products, and the User may solely request to replace the accessories with new ones, which shall be handled after verification by ZWO support team.
If the issue with your ZWO product was caused by certain damage (such as severe damage not covered by the 2-year warranty), you might have to pay the replacement value.

4. For the normal repair or replacement of the Products during the Warranty Period, the User will bear the return cost. When returning the Products, Users shall specify the actual reasons for the damage to the Products, and shall provide the corresponding valid certificates, such as pictures or videos, etc.
For the Products that need to be replaced after being confirmed by ZWO in writing, the User shall return the Products with the complete package, together with all accessories, manuals, etc., to the address designated by ZWO.
By sending back the product to ZWO, the User agrees to pay out-of-warranty fees that may arise during the repair process of the product. ZWO will send back the product after charging.

5. If a User encounters any problem during the use of ZWO Products, you may at any time contact ZWO for technical support via ZWO Support.

For the Products that need to be returned for after-sales service, ZWO will provide the corresponding RMA code for reference.
ZWO will not accept any products having no RMA code that have been returned privately without ZWO written confirmation.

6. If a User purchases the ZWO Products from a ZWO agent, the User may contact the ZWO agent directly for the relevant after-sales service.

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

  1. Avatar


    Will the Helical Focuser work with the ASI120MM-S?


    • Avatar


      Hello! The OAG can work with the ASI120MM-S.


  2. Avatar



    do you know what is the size of the hex screw that holds the prism?



    • Avatar


      Hello! The size is m4.


  3. Avatar


    Hi there,
    recently got the ZWO OAG, but I’m having a real difficulty getting focus on the guide camera (ASI 120mm Mini)

    I’m running a Celestron 8SE, with a .63 Celestron Focal Reducer, with the OAG sitting at around 70mm from the FR.

    Any tips appreciated.



    • Avatar


      Hello! We apologize for this inconvenience. Please contact our support( They have the expertise and resources to assist you effectively.


  4. Avatar

    (verified owner):

    Hi, I want to use this OAG with the Celestron T-adapter for my EdgeHD 8. With the T-adapter I need 55mm of backfocus, so I thought I’d use the image train as suggested here:
    However, the thread of the T-adapter is too long and collides with the prism stalk, so I can’t screw it all the way. This means that my backfocus is off, so I can’t use spacers to fix this.
    Also, when I want to use the shorter T-adapter with the Celestron 0.7x reducer, I can’t use the 0mm M48-M42 adapter because there is no plate to screw against, so I can’t tighten it.
    How could I fix this? Can I use different adapters or do I need a different OAG?


    • Avatar


      Hello! We apologize for this inconvenience. Please contact our support( They have the expertise and resources to assist you effectively.


  5. Avatar


    May you please tell me the best way to spacing my OAG + 183gt + 290 mini in order to reach focus?
    Thank you very much,




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