Ultra-Cat 76 · 30th Anniversary Limited Edition
The Ultra-Cat 76 · 30th Anniversary Edition is a commemorative refractor celebrating three decades of William Optics craftsmanship and innovation. Built upon the acclaimed five-element advanced Petzval optical design, this limited edition of 100 units worldwide combines uncompromising astrophotography performance with a symbolic anniversary finish.
Featuring a unique laser-engraved emblem of a cat embracing “30” ,personally hand-signed by founder William Yang on the lens cover, and accompanied by a 30th Anniversary Certificate, the Ultra-Cat 76 is not only a professional imaging instrument but also a collector’s piece that honors the Cat series legacy.
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 (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.
Anniversary Special
UniGuide 32mm f/3.75
- Lens Type
- Doublet Lens
- Focal Length
- 120 mm
- Diameter
- 32 mm
- Focal Ratio
- f/3.75
- Tube Length
- 147 mm
- Total Weight
- 0.23 kg / 0.51 lbs
- Lens Type
- 5-Element Advanced Petzval
- Lens Elements
- Super ED Glass x2 ED Glass x1 Lanthanum Glass x1 X-Element x1
- Focal Length
- 365 mm
- Diameter
- 76 mm
- Focal Ratio
- f/4.8
- Image Circle
- 50 mm
- Focuser
- WIFD R&P Focuser Compatible with EAF
- Focuser Travel
- 0-20 mm (Ruler to 21mm)
- 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
- 363 mm - 415 mm
- OTA Weight
- 3.81 kg / 8.4 lbs
- Total Weight
- 4.98 kg / 10.98 lbs
Choose options
The Ultra-Cat 76 · 30th Anniversary Edition is a commemorative refractor celebrating three decades of William Optics craftsmanship and innovation. Built upon the acclaimed five-element advanced Petzval optical design, this limited edition of 100 units worldwide combines uncompromising astrophotography performance with a symbolic anniversary finish.
Featuring a unique laser-engraved emblem of a cat embracing “30” ,personally hand-signed by founder William Yang on the lens cover, and accompanied by a 30th Anniversary Certificate, the Ultra-Cat 76 is not only a professional imaging instrument but also a collector’s piece that honors the Cat series legacy.
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 (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.
What's in the box
Main Tube
Bahtinov Cap
M48, M54 Adapter with Wrench
Dual-side Plate
Mounting Ring & Handle bar
Riser Blocks
Soft Carry Case
Allen Key Set
Three Decades of Vision, Inspiring Generations to Come.
Celebrating 30 years of William Optics craftsmanship, the Ultra-Cat 76 brings the acclaimed five-element Petzval design into a commemorative edition. Compact yet powerful, it delivers premium optical performance with a special anniversary finish, engraved emblem, and serialized marking—a telescope that honors the past and inspires the future.
Limited 100 Units
Individually numbered to underscore its exclusivity as a commemorative edition.
Symbolic Laser Engraving
A unique design of a cat embracing the number “30,” honoring the legacy of the Cat series.
Founder’s Signature
Personally hand-signed by William Yang on the lens cover, every telescope is a unique collector’s piece.
Commemorative Certificate
Accompanied by an official 30th Anniversary certificate to mark its special place in William Optics history.
Advanced Petzval
Extra-low Dispersion (ED) glasses
Needs NO Flattener
Never easier to capture deep sky objects
comprehensive configuration
Precision Imaging Adjustment
Sensor Tilt Xterminator (STX)
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 76 · 30th Anniversary Limited Edition 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
Integrated Bahtinov mask
CAT 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.
Expert Review
Small Frame, Big Ambition — My Nights with the UltraCat 76