The mighty Ultra-Cat 131 is finally here! 30th Anniversary Limited Edition will be shipping beginning in March, with a standard edition soon to follow. The Ultra-Cat 131 · 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 30 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 131 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 DesignEliminates field curvature, providing sharp, flat-field images without requiring additional flatteners. 60mm Superior Image CircleFully supports full-frame and medium-format cameras for wide-field and detailed astrophotography, outperforming standard 106mm telescopes. F/4.9 Fast OpticsOffers exceptional light-gathering capability for vibrant deep-sky photography. WIFD (William’s Internal Focuser Design)Patented internal focuser ensures precise, stable, and hassle-free imaging, avoiding balance issues and eliminating vignetting. Anti-Shrink Lens Cell TechnologyMinimizes thermal expansion and contraction, maintaining perfect optical alignment in any environment. Sensor Tilt CorrectorIntegrated and patented design eliminates distortion, optimizing sharpness and detail for professional-level results. Built-In Patented Bahtinov MaskSimplifies focusing for pinpoint precision, a feature that sets it apart from competitors. Patented Handle Bar DesignCombines ergonomic usability with enhanced portability. Lens Type 5-Element Advanced Petzval Lens Elements Super ED Glass x2 ED Glass x1 Lanthanum Glass x1 X-Element x1 Focal Length 648 mm Diameter 131 mm Focal Ratio f/4.9 Image Circle 60 mm Focuser WIFD R&P Focuser Compatible with EAF Focuser Travel 0-20 mm Adapter Included Sensor Tilt Xterminator Rotator M68, 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 Medium Format Full Frame APS-C M4/3 Dovetail Type Losmandy Tube Length 650 mm - 785.5 mm OTA Weight 9.95 kg / 21.94 lbs
