William Optics Gran Turismo 81 APO w/ Internal Focus Design

Introducing the William Optics Internal Focus Design (WIFD) Apochromatic Series. This innovative and revolutionary design combines a precision (patented) internal focusing mechanism with the highest quality optics available, providing the ultimate Apochromatic refractor for astrophotography. Designed from the ground up with the ability to handle the newest generation of large, heavy, high-resolution cooled cameras, the rock-solid optical tube assembly is uncompromised in quality. The movement of the focuser is integrated inside the main tube assembly, so there are no movements of a focuser drawtube visible from the outside. The user can enjoy the benefits of a traditional two speed fine focuser, while not worrying about limitations typically found in traditional rear mounted focusers.

Focuser Design

William Optic's new design includes the patented WO center focuser with precise internal sliding of fixed optics to prevent image shift. The integrated position viewing window on the focuser provides instant verification of the graduated numerical display. The smooth rack and pinion design is incorporated into the focuser to provide super fine adjustability for critical focus. The internal movement of the optical elements is protected from the elements and can’t come out of alignment. The redistribution of weight allows for better balance during imaging sessions.

Design Principle

The WIFD series will allow for many sizes and is not limited to smaller refractors. Additional optical designs are possible to meet various photographic requirements enhancing the line to include a number of apertures and fast focal ratios.

Inspired by the tremendous success of the WO CAT series of astrographs, William Optics has advanced the capabilities of astrophotography to the next level with this "no weight limit on photo accessories" design. The solid tube where accessories are attached, has a rigid design, and will not flex or exhibit any change in the optical path regardless of the weight of the camera and filter wheel attached to it.

Cat Design

Improved "CAT" design ring tubes and dovetail base are lighter while remaining equally rigid. The new design allows for better balance with heavy accessories, and has integral placement of the focuser knobs, providing easy access to focusing during imaging. Included is the popular WO saddle bar handle, critical for rigid guidescope mounting and autoguiding performance.

Super Smooth Field Rotator. Our field rotator design features smooth camera rotation with markings for degrees and a locking thumbscrew to prevent accidental camera movement, also new Electric Rotator will be available in near future.

William Optics FLAT6AIII Adjustable Field Flattener

The William Optics Adjustable Field Flattener improves the flat-field imaging performance of William Optics GT71, GT81, Z81, and Z103 refractors.

Features of the William Optics Adjustable Field Flattener

APO triplet optics made with Ohara glass.
Fully multi-coated to provide bright and flat field across 97% of full-frame sensors.
Built with M63 threads on the telescope side.

The following telescope models can be used with the William Optics FLAT6AIII Adjustable Field Flattener

Amount of Adjustment:
GT71 - 9.1mm
GT71 - 9.1mm
GT81 - 7.1mm
Z103 - 2.5mm
Z81 - 5.2mm

Back Focus:
GT71 - 64.1mm
GT71 - 9.1mm
GT81 - 62.1mm
Z103 - 57.5mm
Z81 - 60.2mm

Image Circle:
GT71 - 44mm
GT71 - 9.1mm
GT81 - 44mm
Z103 - 43mm
Z81 - 44mm

William Optics UniGuide 32mm Guide Scope - Red

The William Optics UniGuide slide-based guide scope is a great addition to your William Optics telescope set-up. You'll get the perfect focus you need every time!

Comes with an adjustable field flattener and a red 32mm guide scope
The new Apochromatic Series with Internal Focus Design (WIFD)
The new design includes the patented WO center focuser with precise internal sliding of fixed optics to prevent image shift
The WIFD series will allow for many sizes and is not limited to smaller refractors
Improved "CAT" design ring tubes and dovetail base are lighter while remaining equally rigid

William Optics Gran Turismo 81 w/ Internal Focus Design APO
Bag
Saddle bar handle
William Optics FLAT6AIII Adjustable Field Flattener
William Optics UniGuide 32mm Guide Scope - Red

Gran Turismo

William Optics Gran Turismo 71 APO Refractor - Red

William Optics Gran Turismo 81 APO Triplet Refractor Telescope - Gold

William Optics Gran Turismo 81 APO w/ Internal Focus Design, Field Flattener & UniGuide