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


Sale price$173 CAD
In stock: 7 unit(s) - Most orders placed by 2PM EST will be shipped out the same day (weekdays)


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.



Additional Resources

You may also like

Recently viewed