William Optics GT-81 II - Checked & Tuned
 William Optics GT-81 II - Checked & TunedWilliam Optics GT-81 II - Checked & Tuned 

William Optics GT-81 II - Checked & Tuned

£1,149.00✓ 2 year warranty


Unavailable please contact us.

New 2019 version due soon!

About this product

Model:  wo-gt-81_II_2018
Part Number:  A-F81GTII

Latest Model GT-81 II Triplet

The new William Optics GT-81 II APO Triplet refractor features a 3-element f/5.9 objective with Ohara FPL-53 extra-low dispersion glass for optimum colour correction and a sturdy 2.5-inch, dual speed 1:10 Rack and Pinion focuser.

ES Reid Checked Telescope

Es Reid is highly regarded in the optical industry so to ensure our William Optics triplet refractors perform at their very best we send them to him for checking and, if necessary, tuning on his optical bench. 

You can order your telescope with confidence knowing it will have well figured optics, negligible false colour and spherical aberration, and no astigmatism (the bane of any optical system!). Star shapes will be round, not triangular, oval or egg-shaped!

You know it makes sense :-) 

Checked & tuned, for details see here

The William Optics GT-81 II APO Triplet refractor features a 3-element f/5.9 objective with an Ohara FPL-53 extra-low-dispersion glass element for optimum colour correction and a new upgraded dual-speed 2.5-inch 1:10 Rack and Pinion focuser with no image shifting. 

The Hotech SCA Field Flattener is an excellent match for this telescope.  

The William Optics 0.8x focal reducer is also available to reduce the focal-ratio to a fast f4.72. 

An excellent choice for astrophotography!

Includes mounting rings,  guiding rings,  new dovetail plate, 2.5" R&P Focuser,  patented Bahtinov Mask Cover and high quality soft carry case.


    Optically Unbeatable

  • 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.
  • This F/5.9 lens is ideal for astrophotography.

    2.5" Rack & Pinion Focuser

  • New robust 2.5" Rack & Pinion focuser with 1:10 dual speed: a treat to use during astrophotography. No image shifting (capacity 6.8kg / 15lb)!
  • Comes with two locking screws on angled positions for heavy load applications.
  • Chromed, soft thumbscrews, easy to use even with gloves on.

    Simply Beautiful Finish

  • Pure William Optics quality fit and finish: powder-painted white CNC-machined Aluminium tube, gold/red or blue trim finish, retractable dewshield, dewshield cap.
  • Top quality anodising.
  • Very compact for carrying on flights.

    Attention to Details

  • 2" & 1.25" adapter included in the price.
  • Anti-marring brass compression rings.

Eyepiece Field of View Simulator

What's in the box

  • Telescope OTA
  • Vixen style dovetail & mounting rings
  • Guiding / Finder rings
  • 2" to 1.25" Adapter
  • Soft Carry Bag


Aperture 81mm
Focal Ratio F/5.9
Focal Length 478mm
Resolving Power 1.43"
Limiting Magnitude 12.2
Objective Type Three element with FPL-53 Air Spaced, Fully Multi-Coated,STM coatings
Lens Shade Retractable
Rack and Pinion   Focuser 45mm drawtube, 1:10 fine focus


1.25" Adapter
Field Stops Knife-Edge Baffles
Dovetail Vixen style dovetail and mounting rings.
Tube Diameter 90mm
Tube Length (390 mm) Fully Retracted
Tube Weight 3.84kg

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