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ZWO Off Axis Guider

ZWO Off Axis Guider


Regular price £116.00
Regular price Sale price £116.00
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ZWO has recently upgraded their Off Axis Guider (OAG) in early 2018, and we have refreshed both the product details and visuals to mirror these enhancements.

Features of the ZWO OAG Adapter:

  • Lightweight design with precision machining
  • Compact profile with a 16.5mm thickness
  • Incorporates a large 8x8mm mirror for improved light reflection
  • Enables the attachment of a guide camera adjacent to the primary imaging camera, eliminating the need for a separate guide scope
  • Offers versatile compatibility with your existing camera and telescope setup through T2 (M42*0.75) and M48 threading
  • Fully supports all ZWO ASI cameras, though we advise consulting us for optimal guiding camera recommendations (Note: The ASI174 model may experience significant vignetting due to its larger chip size, making smaller chip cameras preferable for guiding)
  • Ensures robust stability and a secure connection to your telescope.

Contents of the Package:

  • OAG body (includes a 1.25" holder, 5mm extender, and M42 adapter)
  • M48 adapter for the main imaging camera
  • M48 to M42 adapter for telescope connection and flat lens
  • Hex key (Allen wrench)


  • Mechanical and connection diagrams are provided for reference.

Instructions for Use:

  1. Begin by calculating the necessary distance for your imaging setup. For instance, to achieve a 55mm back focus distance with an ASI071 camera, combine a 17.5mm + 21mm extender with the OAG's 16.5mm thickness.
  2. Remove the guider prism and connect the OAG body to your telescope.
  3. Reinsert the prism into the OAG body.
  4. Attach your guide camera.
  5. Depending on your setup, affix either the T2 or M48 adapter to your imaging camera.
  6. Secure the camera onto the OAG, ensuring it's correctly positioned, and tighten the three thumb screws.
  7. Once the setup is complete, verify that the prism does not obstruct the imaging area.

Adjust the focus of the guiding camera using the provided screw. It's advisable to perform this adjustment during daylight to confirm that both the imaging and guiding cameras can achieve focus simultaneously.

ZWO OAG Adapter features

  • Lightweight and beautifully machined
  • 16.5mm thickness
  • Large prism: 8*8mm (actually, it's a mirror)
  • Allows the use of a guide camera in off axis position next to the main imaging camera without the need for a guide scope.
  • Flexible adaptation to your camera and telescope via  T2 (M42*0.75) and M48 threads
  • Fully compatible with all ZWO ASI cameras, but please contact us about which ZWO cameras we recommend for guiding. (The ASI174 chip is a bit too big for this mirror, so there will be strong vignetting in the guide image, therefore we'd recommend to use cameras with smaller chip for guiding.)
  • Good stability, stiff connection to the telescope

What's in the box (see above image):

  • OAG body(with 1.25″ holder and 5mm extender and M42 adapter)
  • M48 adapter for main imaging camera(in the box)
  • M48-M42 adapter for telescope and flat lens(in the box)
  • Hexagon wrench (Allen key)

Mechanical Diagram

Connection Diagram:

How to use it:

1.   start with caculating the correct required distance for your imaging train.

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 adapter on the imaging camera according to your the mount type

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

7. Setup is complete

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 to do it during the day to make sure that the imaging camera and guiding camera can reach focus at the same position.

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