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IMPORTANT: Our store is located in Canada. All orders that include products manufactured outside of Canada or USA will be subject to tariffs and duties, regardless of the order value. US customers are responsible for all applicable duties and tariffs, and those will be billed by the carrier, except for the Lacerta upgrade kit, for which we collect them at checkout.
IMPORTANT: Our store is located in Canada. All orders that include products manufactured outside of Canada or USA will be subject to tariffs and duties, regardless of the order value. US customers are responsible for all applicable duties and tariffs, and those will be billed by the carrier, except for the Lacerta upgrade kit, for which we collect them at checkout.
ZWO OAG-L

ZWO OAG-L

by ZWO
SKU ZWO-OAG-L
$199.00 - $199.00
$199.00
$199.00 - $199.00
$199.00
Price Match Policy!
  • Large 12mm x 12mm prism for brighter guide stars
  • M68, M54, and M48 connection options
  • 17.5mm thickness preserves 55mm backfocus
  • Designed for ZWO ASI Mini guide cameras
  • Supports full-frame and APS-C imaging sensors
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  • Description
  • FAQ
  • Specifications
  • In the Box
  • Downloads
  • Warranty

  • ZWO M68 Large Off-Axis Guider (OAG-L)

    The ZWO OAG-L M68 Off-Axis Guider uses a large 12mm x 12mm prism to intercept more light, improving guiding accuracy for full-frame and APS-C sensors. Its rigid, 17.5mm body maintains the standard 55mm backfocus distance in your imaging train, while the included 5mm thick tilt plate uses M48 threads for a secure connection to your corrector or flattener.

    Large 12mm x 12mm Prism for Brighter Guide Stars

    The core of the OAG-L is its oversized 12mm x 12mm prism, which provides a significantly larger surface area to send light to your guide camera. This design delivers a bright, clear view of potential guide stars, even in sparse star fields. With an effective light-passing aperture of 11.7mm x 8.3mm, you can use fainter stars for guiding, resulting in more consistent tracking and sharper final images.

    Rigid, 17.5mm Profile for Full-Frame Stability

    Engineered for modern imaging trains, the OAG-L adds only 17.5mm of backfocus, making it easy to integrate while maintaining the critical 55mm spacing required by most correctors. ZWO removed internal threads in favor of a direct, bolt-on connection between the OAG, filter wheel, and camera, creating a solid, flexure-free imaging stack. This rigidity is critical when using full-frame sensors like the ASI6200, ensuring no tilt or sag ruins long exposures.

    ZWO OAG-L vs. Previous M68 OAG

    The primary advantage of the OAG-L is its larger 12mm x 12mm prism. This upgrade allows it to gather significantly more light than the previous generation M68 OAG, directly improving the signal-to-noise ratio at the guide camera. This makes finding and locking onto guide stars easier and more reliable, especially with longer focal length telescopes where the field of view is narrow.

    Helical Focuser for ZWO ASI Mini Cameras

    This off-axis guider is specifically designed for ZWO's ASI Mini guide cameras, such as the ASI174MM Mini or ASI220MM Mini. A precise helical focuser allows you to perfectly match the focus of your guide camera to your main imaging camera. Once you achieve focus during the day on a distant object, you can lock it down, ensuring both your main camera and guider reach focus simultaneously under the stars.

  • Which guide cameras are compatible with the ZWO OAG-L?

    The ZWO OAG-L is designed exclusively for use with ZWO ASI Mini series guide cameras. This includes popular models like the ASI174MM Mini, ASI220MM Mini, and ASI120MM Mini. It is not compatible with standard 1.25" barrel cameras or non-mini ZWO cameras.

    Will the ZWO OAG-L cause vignetting with my full-frame camera like the ASI6200?

    No. The ZWO OAG-L is designed with a large clear aperture to fully support full-frame sensors without vignetting, provided the prism is positioned correctly. For full-frame cameras like the ASI6200 or ASI2600, you should position the prism so it does not physically obstruct the main imaging sensor's light path.

    How does the OAG-L improve guiding over a separate guide scope?

    An off-axis guider eliminates differential flexure, which is the tiny amount of mechanical sag or bending that occurs between a main telescope and a separate guide scope. By using the same light path for both imaging and guiding, the OAG-L ensures the guide camera sees the exact same movement the main camera does, leading to more accurate guiding corrections and sharper stars.

    What is the backfocus consumption of the ZWO OAG-L?

    The main body of the ZWO OAG-L consumes 17.5mm of backfocus. This allows it to fit comfortably within the standard 55mm backfocus distance when paired with a ZWO filter wheel and camera.

    How do I attach the ZWO OAG-L to my telescope and camera?

    The ZWO OAG-L bolts directly to a ZWO 2" or 36mm filter wheel, which then bolts to the camera. On the telescope side, it includes an M48 tilt adapter for connecting to most field flatteners or correctors. Optional M54 and M68 tilt adapters are also available for different thread standards.

    Is the ZWO OAG-L a good choice for a fast Newtonian telescope?

    Yes, but with a consideration. In very fast optical systems (f/4 or faster), the OAG's prism can cast a slight shadow on the main imaging sensor if it's lowered too far into the light path. You must find the optimal balance between prism height for bright guide stars and minimizing any potential obstruction of the main sensor.

  • SKU Number ZWO-OAG-L
    MPN ZWO OAG-L
    Warranty ZWO - 2 Years

    • M68 Large Off-Axis Guider

      × 1

    • M48 Sensor Tilt Plate (5mm)

      × 1

  • ZWO 2-Year Warranty