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William Optics Ultra-Cat 56

William Optics Ultra-Cat 56

New product

William Optics Ultra-Cat 56

William Optics Ultra-Cat 56, a 5-element Petzval astrograph designed for wide-field astrophotography. Featuring a 56 mm aperture, 269 mm focal length and f/4.8 focal ratio, it delivers a 50 mm image circle compatible with full-frame cameras without requiring an external field flattener. Its lightweight and compact design makes it an ideal travel imaging telescope.

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William Optics Ultra-Cat 56

Description

The William Optics Ultra-Cat 56 is the most compact member of the Cat series. It has been specifically developed for wide-field astrophotography by combining a lightweight structure, advanced mechanics and a sophisticated 5-element Petzval optical design.

Its 56 mm aperture, 269 mm focal length and fast f/4.8 focal ratio make it particularly suitable for imaging large nebulae, extensive star fields and wide deep-sky regions.

The optical design uses a proprietary 5-element Petzval system developed by William Optics. This architecture provides a naturally flat field without requiring an external field flattener. The 50 mm image circle supports full-frame sensors while maintaining high image quality across the entire field.

The optical assembly incorporates two Super ED elements, one ED element, one lanthanum element and an additional optical element to reduce chromatic aberration and deliver high-contrast images with accurate colour reproduction.

Focusing is handled by the WIFD Rack & Pinion focuser, fully compatible with electronic autofocus systems such as the EAF. Its internal focusing design improves mechanical balance and minimizes flexure issues commonly encountered with heavy imaging setups.

The integrated Sensor Tilt Xterminator allows fast sensor tilt adjustment without removing the camera. An integrated camera rotator provides precise framing control while maintaining mechanical stability.

The telescope is supplied with a laser-engraved integrated Bahtinov mask, CAT carrying handle, mounting ring, Vixen and Arca-Swiss compatible dovetail plate, M54 and M48 adapters and a soft carrying case.

Combining portability, full-frame compatibility and a fully corrected imaging field without additional accessories, the Ultra-Cat 56 is an excellent solution for portable wide-field astrophotography.

Technical Specifications

  • Manufacturer: William Optics
  • Model: Ultra-Cat 56
  • Type: Petzval astrograph
  • Optical design: 5-element Petzval
  • Aperture: 56 mm
  • Focal length: 269 mm
  • Focal ratio: f/4.8
  • Image circle: 50 mm
  • Full-frame compatible
  • APS-C compatible
  • Micro 4/3 compatible
  • Two Super ED elements
  • One ED element
  • One lanthanum element
  • One additional optical element
  • Fully multi-coated optics
  • Integrated field correction
  • No field flattener required
  • Focuser: WIFD Rack & Pinion
  • EAF compatible
  • Focuser travel: 30 mm
  • 1:10 fine focusing ratio
  • Integrated Sensor Tilt Xterminator
  • Integrated camera rotator
  • M54 adapters included
  • M48 adapters included
  • Canon EF compatible
  • Canon RF compatible
  • Nikon F compatible
  • Nikon Z compatible
  • Sony E compatible
  • Pentax K compatible
  • Fuji X compatible
  • Micro 4/3 compatible
  • Vixen dovetail
  • Arca-Swiss compatible
  • Tube length: 296.3 mm to 348.3 mm
  • OTA weight: 2.56 kg
  • Total weight: 3.21 kg
  • Integrated Bahtinov mask
  • Mounting ring included
  • Carry handle included
  • Soft carrying case included
  • Allen key set included

A Familiar Classic, Elevated to Perform.

The Ultra-Cat 56 condenses the series’ 5-element Petzval performance into its most agile, travel-ready form. Built for wide-field imaging, it delivers crisp flat-field precision and vivid color in an ultra-light platform. Purpose-built for sweeping nebulae and vast star fields, the Ultra-Cat 56 lets astrophotographers chase the night sky with total freedom and ease.

Advanced Petzval

Researched and developed by WO, the innovative 5-element Petzval design redefines telescope optics. This advanced system achieves a flawless spot diagram across a medium-format image circle.

Extra-low Dispersion (ED) glasses

Contains 2 Super ED, 1 ED glasses and lanthanum lenses with advanced fully multi-coated, delivering sharp, vibrant images with true-to-life colors, significantly reducing chromatic aberration.

Needs NO Flattener

The Petzval design inherently flattens the field, eliminating the need for an external field flattener.

FOV Performance

Toggle between tabs to see the difference in field of view.

Ultra-Cat 56
Cat 61
Cat 51

Sensor Tilt Xterminator

The Sensor Tilt Xterminator (STX) is an upgraded design that improves upon the traditional Sensor Tilt Adjuster. With the STX, tilt correction can be performed quickly from the side of the assembly, eliminating the need to remove the camera.

The original configuration of 4 pull-in and 8 push-out screws has been streamlined into a more efficient design with 4 push-out and 4 tension screws. Acting like a seesaw, the STX allows for effortless correction by simply loosening one screw and tightening the opposite diagonal one.

Camera Angle Rotator

Adjust camera orientation with precision and confidence, giving you better framing control without compromising rear-end mechanical stability

Compatible with Electronic Motorized Devices

Hassle Free Installation
( No Mounting Bracket Kit required )

Wo patented design

Internal Focuser

The WIFD focusing design relocates the focuser to the center of the telescope, eliminating tube tilt caused by the weight of cameras and accessories. By removing the need for a traditional rear drawtube, the optical path remains fully unobstructed, ensuring clean and precise image performance.

The Ultra-Cat 56 holds three unique patents, ensuring easy and perfect focusing along with precise coaxial image quality, preventing draw tube tilt issues caused by optical misalignment.

Smooth and Accurate Focusing

The precision-engineered Rack & Pinion system in WIFD Focuser ensures smooth and accurate focusing for both visual observation and astrophotography. Its robust design minimizes backlash and delivers reliable performance, even when supporting heavy imaging equipment.

Dual Speed, Ultimate Precision

The 1:10 fine focuser in WIFD series enhances the focusing process by enabling meticulous fine-tuning. This high-ratio mechanism allows for smooth, incremental adjustments, ensuring optimal clarity and sharpness in your celestial images.

Keep track of temp information

A temperature gauge is included in the WIFD focuser knob, allowing astrophotographers to quickly access weather information and adjust equipment settings.

Package Contents

  • William Optics Ultra-Cat 56
  • Mounting ring
  • CAT carry handle
  • Vixen and Arca-Swiss compatible dovetail plate
  • Integrated Sensor Tilt Xterminator
  • Integrated camera rotator
  • M54 adapter
  • M48 adapter