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ZWO M54(M)-M48(F) Adapter - 21mm

ZWO M54(M)-M48(F) Adapter - 21mm

by ZWO
SKU ZWO-M54-M48-21
$25.00 - $25.00
$25.00
$25.00 - $25.00
$25.00
Price Match Policy!
  • Adds exactly 21mm of optical path length
  • Connects M54 male threads to M48 female threads
  • Standard 2-inch filter threading on the M48 side
  • Black anodized aluminum construction minimizes reflections
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  • Description
  • FAQ
  • Specifications
  • In the Box
  • Warranty

  • ZWO M54(M)-M48(F) Adapter - 21mm

    The ZWO M54 to M48 adapter provides a fixed 21mm of extension, bridging the connection between larger M54 threaded correctors and standard M48 threaded accessories like filter wheels or cameras. This adapter is a critical component for achieving precise back focus in imaging trains that require specific, non-standard spacing to reach the sensor at the correct distance.

    Achieving Precise 21mm Back Focus Spacing

    In astrophotography, hitting the exact back focus distance specified by your flattener or reducer is non-negotiable for a sharp, flat field. This adapter adds exactly 21mm of length, allowing you to fine-tune the spacing in your optical train. It's an essential tool when your camera, filter wheel, and off-axis guider combination doesn't add up to the required 55mm or other custom back focus distances.

    Connecting M54 Correctors to M48 Imaging Trains

    Many modern telescopes and full-frame correctors feature a wide M54 threaded output to minimize vignetting. However, the vast majority of imaging accessories, from 2-inch filter wheels to camera T-rings, use the M48x0.75 standard. This ZWO adapter seamlessly converts the larger M54 male thread to the widely-used M48 female thread, ensuring broad compatibility across your equipment.

    • M54 Male Thread: Connects directly to the telescope focuser, field flattener, or reducer.
    • M48 Female Thread: Accepts standard 2-inch filters and connects to your filter wheel, off-axis guider, or camera.
    • Durable Construction: Machined from black anodized aluminum to reduce internal reflections and provide a rigid connection that prevents flexure.

    ZWO's 21mm vs. Other M54-M48 Adapters

    ZWO offers a range of M54 to M48 adapters, and choosing the correct length is critical. The 21mm adapter is not a universal solution but a specific tool for a specific spacing requirement.

    • vs. ZWO 16.5mm Adapter: The 16.5mm adapter is often used to bring a ZWO camera (17.5mm back focus) and a ZWO OAG (16.5mm) to a total of 34mm, leaving 21mm to be made up. This 21mm adapter is that solution. The choice between them depends entirely on the optical path length of the other components in your imaging train.
    • Fixed Length Trade-off: Unlike a variable spacer, this 21mm adapter provides a fixed, rigid extension. This rigidity is a benefit, as it eliminates potential tilt, but it means you must calculate your required back focus precisely before purchasing.

  • What is the main purpose of the ZWO M54-M48 21mm adapter?

    This adapter serves two primary functions: it converts the larger M54 male thread from a corrector or focuser to the more common M48 female thread used by cameras and filter wheels, and it adds a precise 21mm of spacing to help you achieve the correct back focus for your imaging system.

    How do I use the ZWO 21mm adapter to achieve 55mm back focus with my ZWO camera?

    You would use this 21mm adapter as part of a calculated imaging train. For example, if you have a ZWO camera with 17.5mm of back focus and a ZWO filter wheel that is 20mm thick, the total is 37.5mm. To reach 55mm, you would need 17.5mm of spacing, so this 21mm adapter would be too long. However, if your setup required 58.5mm of back focus, this 21mm adapter would be the perfect component to complete the train (17.5mm + 20mm + 21mm = 58.5mm).

    Can I thread a 2-inch filter into the ZWO M54-M48 adapter?

    Yes. The female M48 side of the adapter is threaded to accept standard 2-inch astronomy filters (M48x0.75). This allows you to place a filter within the adapter itself, which can be useful in specific imaging configurations.

    Will this 21mm adapter connect my Sky-Watcher Quattro corrector to an M48 filter wheel?

    Yes, if your Sky-Watcher Quattro coma corrector terminates in M54 male threads, this adapter is designed for that exact scenario. It will connect to the M54 threads on the corrector and present standard M48 female threads for your filter wheel to attach to, all while adding 21mm to the optical path.

    Is the ZWO M54-M48 21mm adapter compatible with non-ZWO equipment?

    Absolutely. As long as your equipment uses the standard M54x0.75 male thread and M48x0.75 female thread conventions, this adapter will work regardless of the brand. It is a universal part for connecting these two common astronomy thread sizes.

    Why would I choose this fixed 21mm adapter instead of a variable spacer?

    A fixed adapter like this 21mm ZWO model offers superior rigidity and eliminates the risk of tilt that can be introduced by some variable or helical spacers. When you know the exact spacing you need, a fixed adapter is the most stable and reliable way to achieve it.

  • SKU ZWO-M54-M48-21
    Connector Side A M54 Male
    Connector Side B M48 Female (2" Filter Thread)
    Length 21 mm

    • ZWO M54 to M48 Extension - 21 mm

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  • ZWO 2-Year Warranty