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ZWO M54 Extension - 16.5mm

ZWO M54 Extension - 16.5mm

by ZWO
SKU ZWO-M54-M54-16.5
$18.00 - $18.00
$18.00
$18.00 - $18.00
$18.00
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  • Optical Length: 16.5mm
  • Connection Side 1: M54x0.75 Male Thread
  • Connection Side 2: M54x0.75 Female Thread
  • Material: Anodized Aluminum
1 in stock
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  • Description
  • FAQ
  • Specifications
  • In the Box
  • Warranty

  • Precision Back Focus for ZWO Full-Frame Systems — The M54 Extension 16.5mm

    The ZWO M54 Extension 16.5mm tube is a purpose-built spacer designed to solve one of the most critical steps in astrophotography: achieving the standard 55mm back focus distance for full-frame ZWO imaging systems. This is not just a generic spacer. It is the specific component required to bridge the gap between a ZWO 2” Filter Wheel (M54) and a full-frame camera like the ASI6200 or ASI2400, completing the optical train with mechanical rigidity and precise spacing.

    Diagram showing the ZWO M54 16.5mm Extension in a 55mm back focus imaging train.

    Achieve the Critical 55mm Back Focus Distance

    Most field flatteners and coma correctors require a sensor distance of exactly 55mm to deliver sharp stars across the frame. The ZWO M54 Extension 16.5mm is a key part of the ZWO system solution. When combined with a ZWO full-frame camera (17.5mm back focus) and a ZWO 21mm M54 spacer, this 16.5mm extension provides the final piece, summing to a perfect 55mm.

    This precision eliminates the need for stacking multiple, less-stable adapters. By using a single, solid spacer, you reduce the potential for optical tilt that can ruin an otherwise perfect image, especially with the demanding tolerances of large, full-frame sensors. It simplifies your setup and provides a reliable, repeatable connection every time you assemble your gear.

    Secure M54 Threading for Full-Frame Payloads

    The ZWO M54 Extension uses M54x0.75 threads on both its male and female ends. This larger diameter provides a more rigid and stable connection than the older M48 standard, which is critical when supporting the weight of a filter wheel and a heavy, cooled full-frame camera. The wider aperture also helps prevent vignetting on large sensors, ensuring the light cone from the corrector reaches the entire sensor without being clipped.

    The male M54 thread connects directly to the filter wheel or camera tilt adapter, while the female side connects to your corrector or off-axis guider. This creates a seamless, all-ZWO train where every component is designed to work together mechanically, preserving the integrity of your optical alignment throughout a long imaging session.

    Close-up of the M54 threads on a ZWO adapter.

    Internal Light Baffling for Maximum Contrast

    The interior of the extension tube is machined with a matte-black, anodized finish. This surface treatment is designed to absorb stray light that might otherwise reflect off internal surfaces and reduce image contrast. While a small component, its contribution to a clean final image is significant, preventing faint, off-axis light from scattering and washing out the delicate details in nebulae and galaxies.

    A Note on System Compatibility

    This extension is engineered as part of the ZWO ecosystem for achieving 55mm back focus. Its 16.5mm length is highly specific to the optical path lengths of ZWO's own cameras and filter wheels. If you are using components from other manufacturers, you must measure your required spacing carefully, as this part may not be the correct length for a mixed-brand imaging train. It represents a trade-off: perfect integration within the ZWO system in exchange for less universal applicability.

    Lightweight and Durable Construction

    Machined from aircraft-grade aluminum, the adapter adds minimal weight to the imaging train. This helps reduce the overall load on your focuser and mount, which is always a consideration with heavy full-frame systems.

  • Which ZWO cameras need the 16.5mm M54 extension for 55mm back focus?

    This spacer is designed for ZWO full-frame cameras like the ASI6200, ASI2400, and ASI2600 when used with the ZWO 2" EFW (20mm path length). The camera's 17.5mm sensor depth plus the 20mm EFW and this 16.5mm spacer totals 54mm, achieving the 55mm standard when threaded onto a corrector.

    Is this the right spacer if I don't use a filter wheel?

    No. If you connect a ZWO full-frame camera (17.5mm back focus) directly to your corrector, you will need a different combination of spacers to reach 55mm, typically a 20mm and a 16.5mm extension combined (or a variable spacer). This 16.5mm piece is specifically for setups that include the 20mm path length of a filter wheel.

    Will this M54 extension cause vignetting?

    No, the M54 diameter is large enough to pass the full light cone from a 2-inch corrector to a full-frame sensor without clipping the edges. It is the preferred standard over M48 for full-frame imaging to prevent vignetting.

    Can I use this adapter with non-ZWO cameras or filter wheels?

    You can, but only if the total optical path length of your components requires exactly 16.5mm of spacing. You must calculate your back focus needs precisely, as this adapter is not a universal solution and is optimized for the ZWO ecosystem.

    Does the ZWO M54 Extension 16.5mm add any tilt?

    As a single, solid-machined component, it is designed to minimize tilt. Using one 16.5mm extension is mechanically more stable and less prone to tilt than stacking multiple smaller spacers to achieve the same distance.

  • Product Code M54-M54-16.5L
    Optical Length 16.5mm
    Male Thread M54x0.75
    Female Thread M54x0.75
    Material Aluminum
    Finish Matte Black Anodized
    • ZWO M54 Extension - 16.5mm

      ZWO M54 to M54 Extension Tube (16.5mm)

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  • ZWO 2-Year Warranty