William Optics Flat GT Flattener for GranTurismo Refractor

William Optics Flat GT Flattener for GranTurismo Refractor: the calculated flattener for your GranTurismo

The William Optics Flat GT is the field flattener for the GranTurismo 71 and 81 apochromats. Each refractor naturally produces a slightly curved focal plane; a flat camera sensor cuts through that, causing stars in the corners to stretch into lines. A flattener corrects that curvature, so stars remain small and round even in the corners. The correction is calculated for full-frame sensors and beyond, which is important with these fast refractors (f/5 to f/7).

With a length of only 22 mm (0.9 inches) and two lens elements in one group, the train remains short, light, and stiff. The included spacer sets the flattener to the correct position for the GT71 and GT81.

The correct sensor distance

Place your camera at approximately 55 mm behind the flattener: the standard backfocus where the William Optics M48 adapters and 48 mm T-rings land precisely. The M48 camera side has an integrated filter thread.

Backfocus deficit?

If your configuration is too short, the William Optics extension for the Flat GT will still bring the train to the correct length.

Featured accessories

Connect your camera with the M48 adapter for your bayonet; the Flat GT extension resolves a back focus shortage.

For whom yes and for whom no

• ✓ Owners of a GranTurismo 71 or 81 who photograph
• Full-frame photographers on a fast apo
• Owners of the ZenithStar series: the Flat61R and Flat73A are calculated for this.

Specifications

You can find more accessories for this merk at the William Optics merk Page.