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ZWO OAG Off-Axis Guider for Astrophotography - ZWO-OAG

In Stock - Ships Today if Ordered by 2pm! (Tues - Fri)

We will price-match Canadian astronomy dealer pricing

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The ZWO Off-Axis Guider helps you guide your astrophotography rig while imaging without the use of a guide scope.  This helps avoid flexure issues that can arise, especially when using long focal length scopes (ask us about our experiences here!). 

Flexure occurs when various factors such as the movement of the equipment causes tiny variable differences in the direction that a guide scope is pointing vs where the imaging scope is pointing, causing distortions in tracking and less than perfect images.

The OAG allows a guide camera to use the imaging scope as the guide scope, eliminating sources of flexure introduced by guide scopes.  The pick-off prism allows the guide camera to use a star near the edge of the image for guiding purposes, while staying far enough out of the light circle as to not cause a shadow on the main imaging sensor.  

The pick-off prism position is adjustable, allowing you to rotate the OAG and move it inwards and outwards in order to identify a good guide star near the edge of the view that helps avoid adjusting the main scope pointing to find a guide star.


  • Lightweight design
  • Minimal 16.5 mm thickness added to the imaging train
  • Large prism surface: 8 * 8 mm
  • No guide scope required!
  • Flexible connections to your camera and telescope (M42 and M48)
  • Fully compatible with all ZWO ASI cameras
  • Good guide camera stability
  • Strong connections


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


Package Includes


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

2.       M48 adapter for main imaging camera

3.       M48-M42 adapter for telescope and flat lens

4.       Hexagon wrench

Mechanical Diagram

OAG-DRAWConnection Diagram


Set Up and Usage

1.  Please calculate the correct required distance needed for your imaging train in order to take into account the 16.5 mm the OAG will take up, if back focus distance is critical


2.  Remove the guider prism section from the OAG body and attach OAG body to the telescope


3.  Insert the prism section into the OAG body


4.  Mount the guide camera onto the OAG


5.  Screw the T2 or M48 adapter on the imaging camera according to your equipment configuration


6.  Mount the camera on the OAG, adjust the camera orientation to your liking and tighten the 3 screws


7. How the final setup looks


Note: Please adjust the prism depth such that it won’t block the light falling on the main imaging sensor

Use the guide camera retaining screw to move the guide camera in order to adjust the guiding camera’s focus.

It's better to adjust the setup in the daytime to make sure imaging camera and guiding camera can reach focus at the same position.



Returns Policy

You may return most new, unopened items within 30 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).

Items that have been opened, damaged or are otherwise unsaleable will be subject to a minimum 10% restocking fee, to be assessed by Telescopes Canada upon receipt of the returned goods

You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).

If you need to return an item, simply login to your account, view the order using the 'Complete Orders' link under the My Account menu and click the Return Item(s) button. We'll notify you via e-mail of your refund once we've received and processed the returned item.


We can ship to virtually any address in the world. Note that there are restrictions on some products, and some products cannot be shipped to international destinations.

When you place an order, we will estimate shipping and delivery dates for you based on the availability of your items and the shipping options you choose. Depending on the shipping provider you choose, shipping date estimates may appear on the shipping quotes page.

Please also note that the shipping rates for many items we sell are weight-based. The weight of any such item can be found on its detail page. To reflect the policies of the shipping companies we use, all weights will be rounded up to the next full pound.

Typographical Errors and Order Cancellations

Telescopes Canada reserves the right to cancel an order due to an error in pricing by Telescopes Canada or one of our suppliers, equipment being no longer obtainable, or other events which are out of our control.

Client-Initiated Cancellations

Client-initiated order cancellations are accepted prior to delivery of the equipment to the customer, thereafter it is a return.

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