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Closed October 10–12 for Thanksgiving weekend
ZWO M42-M48 Adapter - 16.5mm

ZWO M42-M48 Adapter - 16.5mm

by ZWO
SKU ZWO-T2-M48-16.5
CA$25.00 - CA$25.00
CA$25.00
CA$25.00 - CA$25.00
CA$25.00
Price Match Policy!
  • Adds a precise 16.5mm of optical path length
  • Connects male M42 (T2) threads to female M48 threads
  • Essential for achieving standard 55mm back focus with specific ZWO accessories
  • Machined from black anodized aluminum to minimize internal reflections
24 in stock
Qualifies for FREE Shipping in Canada on orders over $500.
  • Description
  • FAQ
  • Specifications
  • In the Box
  • Warranty

  • ZWO M42-M48 Adapter - 16.5mm

    The ZWO M42-M48 Adapter adds a precise 16.5mm of extension to your imaging train, converting the standard M42x0.75 T-thread to the larger M48x0.75 format used by 2-inch filters and many flatteners and reducers. This specific length is a critical component for achieving the standard 55mm back focus with ZWO cooled cameras in imaging trains without an off-axis guider.

    Achieve 55mm Back Focus with ZWO Components

    This 16.5mm adapter is not an arbitrary length; it is specifically engineered to solve a common spacing problem. In an imaging train without an off-axis guider, a ZWO camera with 17.5mm of back focus plus the 21mm T2 extender included with ZWO cooled cameras leaves exactly 16.5mm to reach the 55mm back focus standard required by most field flatteners and coma correctors. This adapter fills that gap perfectly (17.5mm + 21mm + 16.5mm = 55mm).

    Step Up from 42mm T-Threads to a 48mm Clear Aperture

    Connecting an M42-threaded camera directly to a 2-inch filter wheel or corrector can act as a bottleneck for the light cone, potentially causing vignetting on larger sensors. By converting the M42 thread to the wider M48 format over its 16.5mm length, this adapter ensures the optical path remains as unobstructed as possible, preserving field illumination and image quality from edge to edge.

    • M42 Male Interface: Threads into the M42 female T-thread on ZWO cameras, filter wheels, and other M42 accessories.
    • M48 Female Interface: Accepts field flatteners, reducers, and other accessories with an M48x0.75 male thread.
    • Durable Construction: Machined from a single piece of black anodized aluminum, it provides a rigid, non-reflective connection that prevents flexure and stray light.

  • What is the primary use for the ZWO 16.5mm M42-M48 adapter?

    Its primary function is to correctly space a ZWO astronomy camera relative to other accessories to achieve the standard 55mm back focus. Combined with a camera with 17.5mm of native back focus and the 21mm T2 extender, it provides the remaining 16.5mm to complete the optical train (17.5mm + 21mm + 16.5mm = 55mm) in setups without an off-axis guider.

    Will this ZWO adapter work with my full-frame camera and reducer?

    It is not the right part for a full-frame sensor. The camera side is still an M42 thread, which limits the clear aperture, so full-frame sensors such as the ASI6200 or ASI2400 would show vignetting. ZWO full-frame cameras use M54 connections instead. For APS-C and smaller sensors, the M48 female output lets you connect directly to M48 flatteners and reducers.

    Do I need the 16.5mm length for a ZWO ASI camera with 6.5mm of back focus?

    No, this adapter is intended for cameras with 17.5mm of back focus. If your ZWO camera has 6.5mm of back focus, you would typically use a different combination of spacers, often including the 11mm T2 ring that comes with the camera, to reach your target back focus distance.

    Can I use this 16.5mm adapter with non-ZWO equipment?

    Absolutely. As long as your components use the standard M42x0.75 (T2) and M48x0.75 threads, this adapter will function perfectly as a 16.5mm extension and thread converter, regardless of the manufacturer.

    What is the difference between M42 and M48 threads?

    Both are common standards in astrophotography, but they differ in diameter.

    • M42 (T2-thread): 42mm diameter with a 0.75mm thread pitch. It is the long-standing standard on most cameras and 1.25" accessories.
    • M48 (Wide-T): 48mm diameter with a 0.75mm thread pitch. It is used for 2-inch filters and accessories to provide a wider, less restrictive clear aperture for larger sensors.

    Is the ZWO M42-M48 adapter threaded for filters?

    No, this adapter itself is not designed to hold filters. It is a spacer and thread converter. The M48 female thread is intended to accept an M48 male accessory, such as a field flattener or reducer.

  • SKU ZWO-T2-M48-16.5
    Optical Length 16.5 mm
    Camera Side Connector M42 x 0.75 (T2) Male
    Telescope Side Connector M48 x 0.75 Female
    Warranty 2 Years

    • 16.5mm M42 to M48 Extension Adapter

      × 1

  • ZWO 2-Year Manufacturer Warranty