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Product Description
If you're looking for exceptional wide-field imaging performance in a compact astrograph, the William Optics Ultra-Cat 56 delivers in every way. Featuring an advanced 5-element Petzval optical design constructed from premium glass—including Super ED, ED, Lanthanum, and a proprietary X-Element—this telescope produces razor-sharp, well-corrected stars from center to edge. The naturally flat field eliminates the need for an external flattener or back-focus calculations, making camera setup simple and reliable. With a massive 50mm image circle, stars remain pinpoint across Full Frame sensors and beyond, with compatibility extending to Medium Format cameras. Designed specifically for astrophotography, the Ultra-Cat 56 is engineered to elevate both image quality and ease of use.
With a fast f/4.8 focal ratio and a 269mm focal length, the Ultra-Cat 56 is optimized for capturing expansive deep-sky targets with shorter exposure times. The lightweight yet robust optical tube incorporates William Optics' patented Internal Focus Design (WIFD), providing smooth, precise, and vibration-free focusing without introducing vignetting or balance issues. The focuser is fully compatible with electronic autofocusers for hands-free precision. Integrated features such as the Sensor Tilt Xterminator (STX) and built-in rotator allow for fine tilt correction and effortless framing, ensuring uniform sharpness across the entire sensor. Combined with thoughtful engineering and premium build quality, the William Optics Ultra-Cat 56 stands out as a powerful, all-in-one imaging solution for serious astrophotographers.
Key Features
- Advanced 5-Element Petzval Optics: Eliminates field curvature, ensuring sharp, edge-to-edge stars without additional flatteners.
- 50mm Large Image Circle: Fully supports Full Frame cameras, APS-C and M4/3 sensors for optimal performance. Compatible with Medium Format.
- Fast f/4.8 Optics: Superior light-gathering capability, enabling deep-sky imaging with shorter exposure times.
- WIFD (William's Internal Focuser Design): Patented internal rack-and-pinion focuser ensures stable and precise focusing. No vignetting or balance issues — ideal for astrophotography. Compatible with EAF (Electronic Automatic Focuser) for precision focus control.
- Sensor Tilt Xterminator (STX) & Rotator: Integrated tilt adjuster eliminates sensor misalignment, ensuring uniform image sharpness.
- No Flattener Required: The optical design naturally corrects field curvature, simplifying setup.
- Anti-Shrink Lens Cell Technology: Reduces thermal expansion effects, maintaining perfect optical alignment in any climate.
- Patented Bahtinov Mask for Focusing: Built-in focusing aid ensures pinpoint star sharpness with ease.
- Premium Build & Ergonomic Design: Lightweight yet robust (3.21 kg / 7.08 lbs) construction with a sleek anodized finish. Patented handle bar design for enhanced portability and ease of use.
- Versatile Camera Compatibility: Supports Canon EF, RF, Nikon F,Z, Sony E, Pentax K, MFT, and FUJI X mounts.
Included Sensor Tilt Xterminator (STX)
The STX builds upon the foundation of traditional sensor tilt adjusters, offering a streamlined and intuitive design that eliminates the need for cumbersome disassembly. Unlike conventional systems that require camera removal for tilt correction, the STX allows adjustments to be made directly from the side of the assembly, significantly reducing setup time and enhancing ease of use.
By refining the original 4 pull-in and 8 push-out screw configuration into a more efficient 4 push-out and 4 locked screw system, the STX enables precise and controlled adjustments. Operating like a seesaw mechanism, the system allows for effortless corrections—simply loosen one screw and tighten the opposite diagonal screw to achieve fine tilt alignment. This ensures that astrophotographers can make on-the-fly refinements without disrupting their imaging workflow, maintaining pinpoint star performance across the entire frame.
What's in the Box
Specifications
| Design: | 5-Element Advanced Petzval |
| Lens Elements: | 2x Super ED Glass 1x ED Glass 1x Lanthanum Glass 1x X-Element |
| Focal Length: | 269mm |
| Diameter: | 56mm |
| Aperture: | f/4.8 |
| Focuser: | WIFD (WilliamOptics Internal Focus Design) Note: Compatible with EAF |
| Image Circle: | 50mm >Full Frame |
| Tube Length: | 296.3mm-349.3mm |
| Tube Weight: | 2.56kg / 5.64lbs |
| Total Weight: | 3.21kg / 7.08lbs |
| Adapters Included: | Sensor Tilt Xterminator Rotator M54/M48 Camera Adapters |
| T-Mounts Supported: | Canon EF/RF Nikon F/Z Sony E Pentax K MFT (M4/3) FUJI X |
| Camera Formats Supported: | Medium Format (Compatible) Full Frame (Recommended) APS-C M4/3 |
Spot Diagram
What can I see with a William Optics Ultra-Cat 56 WFID APO Petzval OTA (L-UC56)?
Here are some simulated views of common objects. Results with your telescope will vary with viewing conditions, obrits, equipment and more.
Jupiter with
25mm Eyepiece - 11x Magnification
(Sold Separately)
Jupiter with
10mm Eyepiece - 27x Magnification
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Jupiter with
5mm Eyepiece - 54x Magnification
Sold Separately
Moon with 25mm Eyepiece
11x Magnification
(Sold Separately)
Moon with 10mm Eyepiece
27x Magnification
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Moon with 5mm Eyepiece
54x Magnification
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Andromeda with 36mm Eyepiece
7x Magnification
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Andromeda with 25mm Eyepiece
11x Magnification
(Sold Separately)
Andromeda with 10mm Eyepiece
27x Magnification
Sold Separately
