Ultra-Cat 56
$1,090.00 USD before tax and duties. Tax and duties will be collected during checkout.
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.
- Lens Type
- 5-Element Advanced Petzval
- Lens Elements
- Super ED Glass x2 ED Glass x1 Lanthanum Glass x1 X-Element x1
- Focal Length
- 269 mm
- Diameter
- 56 mm
- Focal Ratio
- f/4.8
- Image Circle
- 50 mm
- Focuser
- WIFD R&P Focuser Compatible with EAF
- Focus Travel
- 0-30 mm
- Adapter Included
- Sensor Tilt Xterminator Rotator M54, M48 Camera Adapters
- Optional Flattener
- No Flattener Required
- T-Mount Support
- Canon EF, RF Nikon F, Z Sony E Pentax K MFT (M4/3) FUJI X
- Camera Format
- Full Frame APS-C M4/3
- Dovetail Type
- Vixen ↔︎ Arca-Swiss
- Tube Length
- 296.3 mm - 348.3 mm
- OTA Weight
- 2.56 kg / 5.64 lbs
- Total Weight
- 3.21 kg / 7.08 lbs
Choose options
$1,090.00 USD before tax and duties. Tax and duties will be collected during checkout.
What's in the box
Main Tube
Bahtinov Cap
M48, M54 adapter with wrench
Dual-side Plate
Mounting RingHandle bar
Soft Carry Case
Allen Key Set
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
Extra-low Dispersion (ED) glasses
Needs NO Flattener
FOV Performance
Image Circle: 50 mm
Focal Length: 269 mm
Image Circle: 46 mm
Focal Length: 300 mm
Image Circle: 48 mm
Focal Length: 250 mm
comprehensive configuration
Precision Imaging Adjustment
Sensor Tilt Xterminator (STX)
Learn More
Camera Angle Rotator
Compatible with Electronic Motorized Devices
Hassle Free Installation
( No Mounting Bracket Kit required )
Leading the market
Wo patented design
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.
:
Internal Focuser
Learn More
Integrated Bahtinov mask
Learn MoreCAT Handle Bar
Crafts for enhanced portability and versatility.
Mounting Ring
Designed for seamless functionality without compromising on stability. Engineered with wide surface contacts, this innovative ring ensures a secure fit while enabling fast, easy detachment.
