The Ultra-Cat 56 is a high-performance 56mm apochromatic refractor, engineered for astrophotographers who demand exceptional portability without sacrificing optical precision, color accuracy, and wide-field performance.

Featuring a 5-element advanced Petzval optical design with super ED and lanthanum glass, paired with a fast f/4.8 focal ratio, the Ultra-Cat 56 delivers razor-sharp, perfectly flat images across a 50mm image circle. With a 269mm focal length, it is optimized for Full Frame, APS-C, and M4/3 sensors, and remains fully compatible with Medium Format cameras, making it an ideal ultra-wide-field imaging platform for deep-sky and large-scale nebula photography.

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 Optics 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 (4.31 kg / 9.5 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.

Note

Astrophotography Only
This telescope is specifically designed for astrophotography, and its optical design does not support visual observation.