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ZWO 2" to 1.25" Filter Adapter Ring

ZWO 2" to 1.25" Filter Adapter Ring

by ZWO
SKU ZWO-2-1.25FL
CA$22.00 - CA$22.00
CA$22.00
CA$22.00 - CA$22.00
CA$22.00
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  • Adapts 1.25" Filters to 2" Filter Holders
  • External Thread: M48x0.75 Male (2" Filter Standard)
  • Internal Thread: M28.5x0.6 Female (1.25" Filter Standard)
  • Black Anodized Aluminum Construction
  • Low-Profile Design Minimizes Added Back Focus
3 in stock
Qualifies for FREE Shipping in Canada on orders over $500.
  • Description
  • FAQ
  • Specifications
  • In the Box
  • Warranty

  • Bridge Your Filter Sets — The ZWO 2"-1.25" Filter Adapter Ring

    The ZWO 2"-1.25" Filter Adapter Ring solves a common problem for astrophotographers: it allows you to use your existing collection of 1.25" filters in any standard 2" filter wheel or filter drawer. This simple, precision-machined ring eliminates the need to immediately repurchase your entire filter set when you upgrade to a larger format filter wheel, saving both cost and waste.

    Secure 2" Integration for Your Filter Wheel

    The adapter features standard male M48x0.75 threads on its exterior, the universal standard for 2" astronomical filters. This allows it to mount securely into any slot on a ZWO EFW, a filter drawer, or any other accessory designed to hold 2" filters. The precision threading ensures a flush, tilt-free fit, maintaining the mechanical alignment of your optical train.

    Immediate Compatibility with 1.25" Filters

    Inside the ring, female M28.5x0.6 threads provide a perfect home for any standard mounted 1.25" filter. Simply screw your narrowband, LRGB, or planetary filter into the adapter, and then mount the entire assembly into your 2" holder. This provides a cost-effective way to continue using specialized 1.25" filters, like a high-quality OIII or H-beta, alongside larger 2" filters in the same imaging session.

    Engineered for Minimal Optical Intrusion

    Back focus is a critical resource in any imaging train, and this adapter is designed to consume as little of it as possible. Its low-profile body adds a negligible amount of optical path length. This ensures that you can likely reach focus without having to reconfigure your camera spacing, a crucial benefit for systems with limited back focus to spare.

    An Important Limitation: Sensor Size and Vignetting

    This adapter is an elegant mechanical solution, but it does not change the laws of physics. Using a 1.25" filter with a large sensor, such as an APS-C or full-frame format, will almost certainly cause vignetting, where the corners of the image appear dark because they are not fully illuminated by the filter. This adapter is best used with cameras that have smaller sensors (like the ASI174, ASI290, or ASI533) where the 1.25" filter can illuminate the entire chip.

  • Will this adapter cause vignetting with my camera?

    If you are using a camera with a large sensor (APS-C or full-frame), you will likely experience significant vignetting. The adapter is best suited for cameras with smaller sensors (typically 4/3" format or smaller) where the 1.25" filter can fully illuminate the sensor.

    Does the ZWO filter adapter work in a non-ZWO 2" filter wheel?

    Yes. The adapter uses the standard M48x0.75 thread for 2" filters, making it compatible with any filter wheel, slider, or drawer that adheres to this common standard.

    How much back focus does this adapter add to the optical path?

    The adapter itself is designed to be as thin as possible and adds a negligible amount of optical path length. It should not affect your ability to reach focus in most imaging configurations.

    Can I use this to adapt a 1.25" eyepiece into a 2" focuser?

    No, this is not an eyepiece adapter. This adapter has filter threads on both sides (M48 and M28.5) and is designed exclusively to mount a 1.25" filter into a 2" filter holder.

    Is it better to use this adapter or buy new 2" filters?

    For smaller sensors, this adapter is a very cost-effective solution. For larger sensors, investing in 2" filters is the correct path to avoid vignetting and achieve an evenly illuminated field of view.

  • Type Filter Adapter Ring
    Compatibility Mounts 1.25" Filters in 2" Holders
    External Thread M48x0.75 Male (Standard 2" Filter Thread)
    Internal Thread M28.5x0.6 Female (Standard 1.25" Filter Thread)
    Material Black Anodized Aluminum
    • ZWO 2inch to 1.25inch Filter Adapter Ring

      ZWO 2"-1.25" Filter Adapter Ring

      × 1

  • ZWO 2-Year Warranty