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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 54mm Flattener Extender for GT81 WIFD

William Optics 54mm Flattener Extender for GT81 WIFD

by William Optics
SKU WO-AD-M80-54-M48
$68.00 - $68.00
$68.00
$68.00 - $68.00
$68.00
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  • Provides a precise 54mm of optical length
  • Connects the FLAT68III flattener to M48 imaging trains
  • Designed specifically for the William Optics Gran Turismo 81 WIFD
  • Input Thread: M80 x 0.75 female
  • Output Thread: M48 x 0.75 male
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  • Description
  • FAQ
  • Specifications
  • In the Box
  • Warranty

  • 54mm Flattener Extender for GT81 WIFD

    The William Optics 54mm Flattener Extender is a purpose-built adapter that provides exactly 54 mm of optical length for imagers using the GT81 WIFD telescope and FLAT68III flattener. This single component connects the flattener's M80 x 0.75 female thread to the standard M48 x 0.75 male thread of your camera or filter wheel, creating a rigid, tilt-free imaging train.

    The 54mm Spacer for FLAT68III on the GT81 WIFD

    Achieving a perfectly flat field with the Gran Turismo 81 WIFD and FLAT68III flattener requires precise back focus. This 54mm extender is the critical component for reaching the standard 55mm back focus distance required by most astronomy cameras, with the final 1mm typically accounted for within the camera body itself. It replaces guesswork and spacer stacking with a single, correct-length solution.

    Secure M80 to M48 Threaded Connection

    This extender features a female M80 x 0.75 thread that securely attaches to the FLAT68III, ensuring a wide, stable connection point. The male M48 x 0.75 output thread is the universal standard for 2-inch filters and full-frame imaging accessories. By using a single, machined piece instead of multiple generic spacers, you eliminate potential sources of flexure and tilt that can degrade corner star shapes.

  • Why do I need this specific 54mm Flattener Extender for my GT81 WIFD?

    This 54mm extender is engineered to provide the exact spacing required between the William Optics FLAT68III flattener and your camera sensor when used with the Gran Turismo 81 WIFD telescope. This ensures you achieve the specified 55mm back focus for a flat field and sharp stars corner-to-corner.

    How does the 54mm Flattener Extender help achieve the standard 55mm back focus?

    The total back focus of 55mm is a combination of this extender and the internal optical path of your camera. This adapter provides 54 mm of the required distance. The remaining 1 mm is typically the distance from the M48 thread flange on your camera to the sensor plane itself, a common specification for dedicated astronomy cameras.

    What is the advantage of using this single 54mm Flattener Extender over stacking M48 spacers?

    A single, solid extender provides a much more rigid and stable connection. Stacking multiple smaller spacers can introduce flexure or tilt into the imaging train, which can lead to elongated stars in the corners of your images. This purpose-built extender guarantees alignment and stability.

    Will this 54mm Flattener Extender work with my full-frame camera and 2" filter wheel on the GT81 WIFD?

    Yes. The output thread is M48 x 0.75, which is the standard for connecting to most 2" filter wheels and full-frame camera adapters. You must ensure your total back focus, including the filter wheel and any other adapters, adds up to the required 55mm from the flattener's flange.

    Can I use this 54mm Flattener Extender with a different telescope, like a ZenithStar?

    No, this extender is specifically calculated for the focal length and optical design of the William Optics GT81 WIFD when paired with the FLAT68III flattener. Using it on another telescope will likely result in incorrect spacing and poor image quality, as different telescopes require different back focus distances.

    What are the thread sizes for the 54mm Flattener Extender?

    The extender has two threads:

    • Light-In Side (attaches to flattener): M80 x 0.75 female thread
    • Light-Out Side (attaches to camera): M48 x 0.75 male thread
  • Optical Length 54 mm
    Input Thread (Flattener Side) M80 x 0.75
    Output Thread (Camera Side) M48 x 0.75

    • 54mm Flattener Extender for GT81 WIFD

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  • William Optics 2-Year Warranty