William Optics Ultra-Cat 131 Refractor Telescope
The William Optics Ultra-Cat 131 is the flagship of the Ultra-Cat series, representing the pinnacle of wide-field astrophotography performance. Built around a large-aperture 131mm apochromatic optical system and an advanced 5-element Petzval design, it delivers extraordinary light-gathering power, exceptional color correction, and razor-sharp stars across an expansive, flat image circle.
Designed for serious astrophotographers and observatories alike, the Ultra-Cat 131 combines a fast focal ratio with uncompromising optical precision, enabling stunning deep-sky detail, rich contrast, and immersive wide-field compositions. Its premium mechanical construction, thermal stability, and flagship-level engineering set a new benchmark for large-format astrophotography systems.
Note: This telescope is specifically designed for astrophotography. Its optical design does not support visual observation.
Key Features
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Advanced 5-Element Petzval Design
Eliminates field curvature, providing sharp, flat-field images without requiring additional flatteners. -
60mm Superior Image Circle
Supports full-frame and medium-format cameras for wide-field and detailed astrophotography, offering a larger image circle than conventional 106mm telescopes. -
F/4.9 Fast Optics
Delivers excellent light-gathering capability for vibrant, detailed deep-sky photography. -
WIFD (William's Internal Focuser Design)
Patented internal focuser ensures precise, stable focusing and hassle-free imaging while helping avoid balance issues and vignetting. -
Anti-Shrink Lens Cell Technology
Minimizes the effects of thermal expansion and contraction, helping maintain optical alignment under changing temperatures. -
Integrated Sensor Tilt Corrector
Patented design allows sensor tilt adjustment to optimize image sharpness and detail across the image field. -
Built-In Patented Bahtinov Mask
Simplifies focusing and helps achieve pinpoint focus precision. -
Patented Handle Bar Design
Combines ergonomic handling with enhanced portability. -
Personalized Laser Engraving
Free customization is available for direct purchases, adding a personal touch to your telescope.
Specifications
- Lens Type: 5-Element Advanced Petzval
- Lens Elements: 2 × Super ED Glass, 1 × ED Glass, 1 × Lanthanum Glass, 1 × X-Element
- Focal Length: 648 mm
- Aperture: 131 mm
- Focal Ratio: f/4.9
- Image Circle: 60 mm
- Focuser: WIFD Rack-and-Pinion Focuser, compatible with EAF
- Focuser Travel: 0–20 mm
- Included Adapters: Sensor Tilt Xterminator Rotator; M68, M54, and M48 camera adapters
- Optional Flattener: Not required
- T-Mount Support: Canon EF, Canon RF, Nikon F, Nikon Z, Sony E, Pentax K, MFT (M4/3), FUJIFILM X
- Supported Camera Formats: Medium Format, Full Frame, APS-C, M4/3
- Dovetail Type: Losmandy
- Tube Length: 650–785.5 mm
- Optical Tube Assembly Weight: 11.3 kg / 24.91 lbs
- Total Weight: 13.97 kg / 30.8 lbs
Other Information
- Country of Manufacture: Taiwan