The Gold Standard for Wide-Field
The William Optics Gran Turismo 81 (GT81) has become a staple in the world of high-performance wide-field imaging. It features a triplet objective lens utilizing FPL-53 synthetic fluorite glass, which is widely considered the gold standard for color correction in refractors.
Mechanically, the scope is built like a tank. The 2.5" Rack & Pinion focuser is smooth, robust, and shows zero flex even when loaded with a heavy mono camera and filter wheel. One of its most distinctive "quality of life" features is the patented clear Bahtinov mask integrated into the lens cover—a small detail that makes focusing in the field significantly faster.
Advantages
- Perfect color correction (Zero fringing)
- Patented built-in Bahtinov mask
- Rock-solid 2.5" R&P Focuser
- Top-tier aesthetic and mechanical finish
Limitations
- Backfocus is critical when using the Reducer
- Heavier than 80mm doublets or Petzvals
- Higher price point for the FPL-53 optics
"The GT81 IV isn't just a telescope; it’s a reliable imaging platform. It is rare to find a piece of gear that combines this level of optical excellence with such thoughtful mechanical design."
Technical Specs
Aperture81mm
Focal Length478mm (f/5.9)
Lens TypeFPL-53 Triplet
Focuser2.5" Dual Speed
Reduced FL382mm (f/4.7)
Weight3.9 kg (8.6 lbs)
Image CircleFull Frame Support