William Optics 54mm Flattener Extender for 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.

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.

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.

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.

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.

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