William Optics Flat68III Flattener

William Optics Flat68III Flattener: adjustable top correction for your WO-apo

The William Optics Flat68III is an adjustable backfocus field flattener for larger William Optics apochromats. Each refractor naturally produces a slightly curved focal plane. A flat camera sensor cuts through this, causing stars in the corners to stretch into streaks. A flattener corrects that curvature, ensuring stars remain small and round all the way to the corners.

The optics consist of Japanese Ohara glass with full FMC coating: maximum sharpness and clarity, minimal reflections. You adjust the distance with the knurled locking ring, without loose extension tubes.

On the train

The flattener screws onto the focuser using the M92 thread; the camera side is T2 for the T2 ring for your camera brand. Filters with an M48 thread screw directly onto the flattener, neatly in the light path.

Featured accessories

Combine the Flat68III with the T2 ring for your camera brand; the 45 mm Flat68II/Flat7A adapter serves as a spacer when the setup requires it.

For whom yes and for whom no

• ✓ Astrophotographers with a WO Apochromatic Refractor and M92 focuser
• ✓ How to set backfocus without loose rings
• Owners of the small ZenithStars: choose the Flat61R or Flat73A

Specifications

You can find more accessories for this brand at the William Optics brand page.