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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.
William Optics 48mm T-Mount for Canon
William Optics 48mm T-Mount for Canon
William Optics 48mm T-Mount for Canon

William Optics 48mm T-Mount for Canon

by William Optics
SKU WO-TM-CN-EOS-M48
$39.00 - $39.00
$39.00
$39.00 - $39.00
$39.00
Price Match Policy!
  • Connects M48 (2-inch) Threaded Correctors to Canon EOS Cameras
  • Wide M48 Aperture Eliminates Vignetting on Full-Frame Sensors
  • Adds a Precise 10.6 mm of Optical Length to the Imaging Train
  • Machined from Black Anodized Aluminum
  • Female M48x0.75 Threading
5 in stock
Qualifies for FREE Shipping in CONUS on orders over $350.
  • Description
  • FAQ
  • Specifications
  • In the Box
  • Warranty

  • William Optics 48mm T-Mount for Canon

    The William Optics 48mm T-Mount for Canon is the professional-grade solution for connecting your Canon EOS camera to a modern 2-inch imaging train, featuring a wide M48 female thread to prevent vignetting on full-frame sensors. It adds a precise 10.6 mm to the optical path, a critical constant for calculating the exact spacing required by field flatteners and reducers to achieve sharp stars across the entire frame.

    M48 Threads & 10.6mm Spacing: The Solution for Full-Frame Canon Imaging

    This adapter solves the most common bottleneck in DSLR astrophotography: the restrictive M42 "T-thread." By using the larger M48 x 0.75 female thread, this T-mount provides a wider, un-obstructed light path from your flattener or reducer to your camera's sensor. This is essential for owners of full-frame Canon cameras, as it eliminates the vignetting (darkened corners) that M42 adapters often create.

    The fixed optical length of 10.6 mm is designed for precision. When paired with a Canon EOS camera body, which has a native flange focal distance of 44mm, this adapter brings your total back focus to 54.6mm. This is within a millimeter of the 55mm standard required by most field correctors, allowing you to achieve a flat field with minimal or no additional spacers.

    William Optics M48 vs. Standard M42 T-Ring: A Wider Path to the Sensor

    While standard M42 T-rings are common, they were designed for older film formats and can act as a choke point for the light cone in a modern imaging setup. The William Optics M48 T-Mount is purpose-built to overcome this limitation.

    • Standard M42 T-Ring: The smaller 42mm thread diameter often vignettes the corners of full-frame and even some large APS-C sensors, forcing you to crop your final images or spend time correcting gradients in post-processing.
    • William Optics M48 T-Mount: The larger 48mm thread diameter provides a clear aperture that fully illuminates sensors up to 44mm diagonally. This ensures your expensive full-frame sensor receives all the light your telescope collects, resulting in brighter, evenly illuminated frames from edge to edge.

  • What is the advantage of the William Optics M48 T-Mount over a standard M42 T-ring for my Canon EOS camera?

    The primary advantage is the larger M48 thread diameter, which prevents vignetting (darkening of the corners) on full-frame and large APS-C camera sensors. A standard M42 T-ring can physically block some of the light cone, while the M48 mount ensures the entire sensor is evenly illuminated.

    Will this M48 T-Mount work with my William Optics refractor and flattener?

    Yes, this T-mount is specifically designed to integrate with William Optics flatteners and other correctors that output an M48 male thread and require approximately 55mm of back focus. The 10.6 mm optical length of this adapter is a key part of that calculation when used with a Canon EOS camera body.

    How do I calculate back focus using the 10.6 mm optical length of this William Optics T-mount?

    You add the adapter's optical length to your camera's flange distance. For a Canon EOS camera, the flange distance is 44mm. So, the total distance from the T-mount's M48 thread to your sensor will be 44mm + 10.6mm = 54.6mm. You can then use thin M48 spacers to reach the exact back focus required by your specific flattener or reducer, which is typically 55mm.

    Is this adapter compatible with both full-frame and APS-C Canon EOS cameras?

    Yes, it is compatible with any camera that uses the Canon EOS mount. While it provides the most significant benefit for full-frame cameras by preventing vignetting, it works perfectly with APS-C models as well, providing a secure, wide-aperture connection to your telescope.

    Can I use 2-inch filters with the William Optics M48 T-Mount?

    This adapter itself does not have threads for a filter. Filters should be placed earlier in the imaging train, typically by threading them into a dedicated filter drawer, a filter wheel, or directly onto the nosepiece of the flattener/reducer before you attach this T-mount.

    Will this adapter let me attach my Canon EOS camera to a Schmidt-Cassegrain telescope for imaging the Orion Nebula (M42)?

    Yes, provided your Schmidt-Cassegrain (SCT) is equipped with a focal reducer or flattener that terminates in male M48 threads. You would thread this T-mount onto the corrector, and then attach your Canon EOS camera to the bayonet mount to image large targets like the Orion Nebula (M42).

  • Telescope Side Connection M48 x 0.75 Female Thread
    Camera Side Connection Canon EOS Camera Mount
    Optical Length 10.6 mm

    • William Optics 48mm T-Mount for Canon EOS

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  • William Optics 2-Year Warranty