William Optics

0.8x Reducer Flattener for GT71 /GT81 /Z103


  • Sale
  • Regular price $229.00

Yes, our inventory is accurate!

Qualifies for Free Ground Economy Shipping (CONUS Only)

This William Optics 2" Field Flattener and Reducer has been designed to optimize the flat-field imaging performance of William Optics GT71, GT81, Z81 & Z103 refactors. The APO triplet optics of the Field Flattener and Reducer are made with Ohara glass and fully multi-coated to provide good illumination and a beautifully flat field across 97% of full frame sensors. The reducing factor is 0.8X.

Designed with M63 threads on the telescope side, the Field Flattener and Reducer will thread directly into the telescope. Just remove the three screws on the focuser adapter, take off the adapter, and thread the focal reducer/field flattener on in it's stead. The Field Flattener and Reducer has 2" threads on the opposite side to accept a 48mm (Wide) T ring for your DSLR. There is even a slot behind the 2" threads to accept an M48 filter.

The Field Flattener and Reducer is adjustable to help you achieve the proper back focus. Adjustment distances & back focus, as well as the image circle measurement for each of the telescopes are listed below.

Full frame size

  • Designed with nearly Full frame chip-size DSLR cameras in mind.
  • FMC tripllet APO design.
  • Produced entirely with the best Ohara optical glasses.


  • Reducing factor 0.8X.
  • Adjustable design, for perfect back focus it can be used with other models of refractor
  • 48mm filter ready

Superb Finish

  • William Optics polished anodized finish.
  • All internal surfaces threaded and blackened to prevent reflections.

Easy to Use

  • Will accept any standard 48mm wide T-ring for your camera. Not compatible with smaller 42mm T rings.

Suitable for

  • Newer GT71, GT81, Z81, Z103 scopes that have a female M63 thread.  Please check your telescope before ordering.  

Amount of adjustment for DSLR or mirrorless camera:

  • GT71 - 9.1 mm
  • GT81 - 7.1 mm
  • Z103 - 2.5 mm
  • Z81 - 5.2 mm

Back focus:

  • GT71 - 64.1 mm
  • GT81 - 62.1 mm
  • Z103 - 57.5 mm
  • Z81 - 60.2 mm

Image Circle:

  • GT71 - 44.4 mm
  • GT81 - 44.4 mm
  • Z103 - 43.1 mm
  • Z81 - 44.3 mm