Overview of the William Optics Internal Focus Design (WIFD)
If you are an astrophotographer, you've likely looked into upgrading your telescope's focuser at some point. The stock focusers on many telescopes are simply not capable of supporting the weight of today's heavy image trains that can include a rotator, off-axis guider, filter wheel, camera, and more. This can cause the focuser to slip out of focus, or even worse: cause dreaded sensor tilt, which can be daunting to fix.
The innovative team at William Optics has been hard at work trying to resolve this problem, and have now announced their patented solution: the William Optics Internal Focus Design, or WIFD for short.
The WIFD is a revolutionary telescope design that moves the focuser from the rear exterior of the telescope to the inside. The WIFD focuser drawtube stays housed in the main chassis of the telescope, which results in a dramatically more stable focuser:
Revolutionary WIFD Focuser: A New Era in Precision Focus
The WIFD features a smooth rack and pinion design that is incorporated into the focuser to provide precise adjustability for critical focus. The internal movement of the optical elements is protected from the elements and can't come out of alignment. This redistribution of weight allows for better balance during imaging sessions.
New Temperature Compensated Lens Cell Design
Super Smooth Field Rotator
The included field rotator features smooth camera rotation with markings for degrees and a locking thumbscrew to prevent accidental camera movement.
Scalability of the William Optics Internal Focuser Design
The WIFD will not just be limited to the GT81, and will be adapted to many sizes of refractors. Additional optical designs are possible to meet various photographic requirements enhancing the line to include a number of apertures and fast focal ratios.
Please note: The focuser travel does not extend over the full range of the markings shown on the telescope tube. This is normal in all WO WIFD/Pleiades telescopes and not a defect in your particular unit.
William Optics WIFD GT81 Specifications
- Telescope Optical Design: APO Triplet Refractor
- Focal Length: 478mm
- Diameter: 81mm
- F/ Ratio: f/5.9
- Compatible Reducers & Flatteners: FLAT6AIII 0.8x Reducer/Flattener (not included) | FLAT68III 1.0x Field Flattener (not included; also requires additional # AD-M80-45-M48 adapter)
- Focuser: WIFD, Compatible with EAF
- Back focus specifications:
- Telescope only: Available maximum backfocus is 183.4mm from the base of the M63 male thread. Telescope can focus as long as your image sensor is placed anywhere between the scope and 183.4mm.
- Telescope with P-FLAT6AIII flattener (sold separately): 55mm with flattener adjustment scale set to 7.1mm
- Telescope with P-FLAT68III flattener (sold separately and requires use of an additional adapter): 55mm with flattener adjustment scale set to 10.9mm
- Image circle size (OTA only, OTA with FLAT6AIII, OTA with FLAT68III): All 44.4mm (full frame coverage)
- OTA weight: 7.3 lbs (3.3 kg)
- Total weight (with rings & dovetail plate): 9.9 lbs (4.5 kgs)
- Tube length (dew shield fully retracted): 420mm
- Tube length (dew shield fully expanded): 500mm
- Dew shield OD: 121mm / 4.76"
- Color: Red
- Lens Glass Type: FPL-53
- Strehl Ratio: 0.95+
- Camera Format: Full Frame | DSLR | Mirrorless | CMOS | CCD
- Zygo Test Report: Included
- M48 T-Mounts Supported: Canon EF, RF | Nikon F, Z | Sony E | Pentax K | Micro Four Thirds (M4/3) | FUJI X
What's in the Box
- William Optics WIFD GT81 81mm f/5.9 Apo Refractor OTA - Red
- Lens cover with Bahtinov Mask
- Zygo Test Report
- Soft Case
Other Information
- Country of Manufacture: Taiwan
