Focus Scientific

William Optics Gran Turismo 81mm f/5.9 Apochromat Refractor OTA (Blue)

The new GT81 three-element super APO offer superb quality for imaging and visual use at an affordable price. The pristine white finish and the elegant blue trim embodies more than just good looks.


  • Triplet air-spaced objective (FPL-53) in adjustable CNC machined ultra high precision lens cell
  • Extremely sharp
  • Excellent color correction
  • Each lens is Fully Multi-Coated with a special super-high transmission coating (STM Coating) on all surfaces
  • The F/5.9 objective is ideal for deep-sky astrophotography
  • 2.5” R&P Ultra robust focuser with 1:10 dual speed: a treat to use during astrophotography, with no image shift and no "Crayford slip"
  • Innovative Bahtinov Mask Cover (Patented) & New Dualside Dovetail Plate (DSD 210) included
  • Pure William Optics quality fit and finish: powder-painted white CNC-machined aluminum tube, blue trim finish, retractable dewshield, dewshield cap
  • Top quality anodizing
  • Very compact for carrying on flights
  • 2" & 1.25" adapter included in the price
  • Anti-marring brass compression rings
  • Though you will never need it, you have a 2-year warranty from WO, and the certainty that we will be there to assist you even beyond that, if you need!
  • Retracted Length: 390mm (15.4")
  • Tube with Rings and Dovetail Weigh: 3.84kg (8.5 lbs)

Standard Package Includes

  • Mounting Rings
  • Guiding Rings
  • New Dualside Dovetail Plate (DSD 210)
  • 2.5” R&P Focuser
  • Innovative Bahtinov Mask Cover (Patented)
  • Soft Carry Case
  • Two-year, no fuss warranty and constant customer service!


  • Aperture: 81mm (3.1")
  • Focal Ratio: F/5.9
  • Focal Length: 480 mm
  • Objective Type: Synthetic Flourite FPL 53 Triplet, Air Spaced, APO
  • Fully Multi-Coated, STM coating
  • Image Circle Diameter: 44mm
  • Lens Shade: Retractable
  • Focuser: 2.5" R&P Focuser with 1:10 Dual Speed micro focuser
  • Focuser Travel: 93mm, graduated in millimeters
  • Features a dual purpose carrying handle/accessory dovetail
  • Dial Type Thermometer Built Into Focuser
  • Bhatinov Mask Cover for Critical Focus
  • 1.25" and 2" Adapter: Compression Rings
  • New Dualside Dovetail Plate (DSD 210)
  • Field Stops: Baffles for Stray Light Suppression
  • Retracted Length: 390mm (15.4")
  • Tube with Rings and Dovetail Weight: 3.84kg (8.5 lbs)
  • Two year warranty