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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.
ZWO M42-M48 Adapter - 16.5mm

ZWO M42-M48 Adapter - 16.5mm

by ZWO
SKU ZWO-T2-M48-16.5
$18.00 - $18.00
$18.00
$18.00 - $18.00
$18.00
Price Match Policy!
  • Adds a precise 16.5mm of optical path length
  • Connects female M42 (T2) threads to male M48 threads
  • Essential for achieving standard 55mm back focus with specific ZWO accessories
  • Machined from black anodized aluminum to minimize internal reflections
2 in stock
Qualifies for FREE Shipping in CONUS on orders over $350.
  • 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 full-frame correctors. This specific length is a critical component for achieving the standard 55mm back focus when connecting ZWO cameras to ZWO filter wheels and off-axis guiders.

    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. When you connect a ZWO camera with 17.5mm of back focus to a ZWO 2-inch filter wheel (20mm thick), this 16.5mm adapter fills the remaining gap perfectly to hit the 55mm back focus standard required by most field flatteners and coma correctors (17.5mm + 20mm + 16.5mm = 54mm, with 1mm for thread depth).

    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 Female Interface: Connects securely to the T-thread on most astronomy cameras, including all ZWO cooled and uncooled models.
    • M48 Male Interface: Threads directly into 2-inch filter wheels, off-axis guiders, and other accessories that use the M48x0.75 standard.
    • 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. It is designed to be used between a camera with 17.5mm of native back focus and a 20mm thick ZWO filter wheel, providing the necessary 16.5mm to complete the optical train.

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

    Yes, this is an excellent choice for larger sensors. By converting the smaller M42 camera thread to the larger M48 format, it helps prevent vignetting (darkening of the corners) that can occur when the light path is constricted by smaller T-threads. It ensures your full-frame sensor is fully illuminated by the corrected field.

    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 male thread is intended to connect to a component that holds filters, such as a filter wheel or a filter drawer.

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

    • 16.5mm M42 to M48 Extension Adapter

      × 1

  • ZWO 2-Year Manufacturer Warranty