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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

ZWO OAG

by ZWO
SKU ZWO-OAG
$128.00 - $128.00
$128.00
$128.00 - $128.00
$128.00
Price Match Policy!
  • Eliminates Differential Flexure
  • Reduces Overall System Weight
  • Includes 1.25" Guide Camera Holder
  • 5mm T2 Extender for Spacing Adjustment
  • M42 and M48 Adapters Included
1 in stock
Qualifies for FREE Shipping in CONUS on orders over $350.
  • Description
  • FAQ
  • Specifications
  • In the Box
  • Downloads
  • Warranty

  • ZWO OAG Off-Axis Guider

    The ZWO OAG integrates guiding directly into your main optical path using an included 1.25” holder for your guide camera. It ships with a 5mm T2 extender and multiple adapters to solve critical spacing and connection challenges, effectively eliminating the differential flexure that can plague separate guidescope setups.

    End Differential Flexure with a 1.25" Integrated Guider

    The ZWO OAG solves the most persistent problem in long-exposure astrophotography: differential flexure. By using a prism to pick off a small portion of the light from your main telescope's imaging cone, it ensures your guide camera and imaging camera see the exact same minute movements. Any tube flexure, mirror flop, or mount shift is seen by both cameras simultaneously, resulting in perfectly round stars even at long focal lengths.

    This design makes a separate, heavy guidescope unnecessary, reducing the overall weight and complexity of your rig. The OAG includes a standard 1.25” holder, making it compatible with a wide range of popular autoguiding cameras.

    Fine-Tune Focus with the Included 5mm T2 Extender

    Achieving simultaneous focus between your main imager and guide camera is critical. The ZWO OAG kit includes a versatile set of adapters to manage the precise spacing required. The package contains M42 and M48 adapters for direct connection to most ZWO cameras, filter wheels, and telescope focusers.

    • 5mm T2 Extender: This crucial spacer helps adjust the distance between the OAG and your main camera, providing the mechanical back focus needed to bring the guide camera into focus.
    • Adapter Suite: With included M42, M48, and M48-M42 adapters, you have the flexibility to connect to nearly any imaging train configuration right out of the box.

    ZWO OAG vs. Traditional 50mm Guidescopes

    While a 50mm guidescope offers a wider field of view for finding a guide star, the OAG provides superior guiding accuracy where it matters most.

    • Zero Flexure: The ZWO OAG physically eliminates differential flexure, a mechanical problem that guiding software cannot correct. This is the single largest source of elongated stars in systems using a separate guidescope.
    • Reduced Weight and Better Balance: By removing the guidescope, mounting rings, and dovetail bar, you reduce the payload on your mount. This improves tracking and allows the mount to perform more efficiently.
    • Long Focal Length Precision: For Schmidt-Cassegrains and Ritchey-Chrétiens, the OAG guides at the same image scale as your main camera. This allows for far more precise corrections than a short focal length guidescope can deliver, leading to fundamentally sharper images.

  • Why should I use the ZWO OAG instead of a guidescope?

    The primary reason is to eliminate differential flexure. This is any small mechanical shift between your main telescope and your guidescope that causes trailing stars, even with perfect guiding. The ZWO OAG uses one optical path for both cameras, making this problem impossible. It also reduces the weight and complexity of your setup.

    Will the ZWO OAG work with my Celestron EdgeHD 8" and an ASI533MC Pro camera?

    Yes, this is an excellent combination. Long focal length systems like the EdgeHD 8" are the most susceptible to differential flexure, making the ZWO OAG the ideal guiding solution. The included M42 and M48 adapters will allow you to connect the OAG to your camera and the telescope's reducer or focuser.

    How do I focus the guide camera with the ZWO OAG?

    First, achieve sharp focus with your main imaging camera. Then, loosen the thumbscrew on the 1.25" holder and slide your guide camera up or down until the stars in your guiding software are also sharp. The goal is to make the distance from the prism to the guide sensor equal to the distance from the prism to the main imaging sensor. The included 5mm T2 extender can be used to adjust the main camera's position to help achieve this.

    I'm imaging the Pelican Nebula (IC 5070). Will I have trouble finding a guide star?

    The Pelican Nebula is in a dense region of the Milky Way, so finding a guide star with the ZWO OAG should be straightforward. The main trade-off of an OAG is a smaller field of view for finding stars compared to a guidescope. In star-poor regions, you may need to rotate your camera to place a suitable guide star onto the prism, but for most deep-sky targets, this is not an issue.

    What adapters come included with the ZWO OAG?

    The ZWO OAG comes with a comprehensive set of adapters to fit most imaging trains. Included are an M48 adapter for 2" filter threads, an M42 adapter for T-threads, and an M48-M42 adapter ring for additional flexibility.

    Can I use a non-ZWO guide camera with this OAG?

    Yes. The ZWO OAG includes a standard 1.25” holder. Any guide camera with a 1.25" nosepiece form factor will fit and can be used for autoguiding.

  • SKU ZWO-OAG
    Warranty 2 Years

    • ZWO OAG Body

      × 1

    • 1.25” Holder

      × 1

    • 5mm T2 Extender

      × 1

    • M42 Adapter

      × 1

    • M48 Adapter

      × 1

    • M48-M42 Adapter

      × 1

    • Hexagon Wrench

      × 1

  • ZWO 2-Year Limited Warranty