An anniversary you can see

Optical excellence without compromise

• 5-element Petzval design for a perfectly corrected, flat image field – without the need for an additional flattener.

• Super ED glass, two ED elements and one lanthanum element for maximum colour fidelity and sharpness.

• 131 mm aperture, 648 mm focal length, f/4.9 – ideal for deep sky astrophotography with high light intensity.

• WIFD 60 mm R&P Focuser, EAF-compatible, with 0–20 mm Sensor Tilt Xterminator Rotator for perfect adjustment.

• Extensive camera compatibility from Canon EF/RF to Nikon F/Z to Sony E, Fuji X and MFT.

• Individual Numbering: Each unit is uniquely serialized (01–30).

Weighing just under 10 kg and measuring 650–785 mm in length, the Ultra-Cat 131 is remarkably portable for its performance class. Its high-quality mechanics, precise rotation and focus solution, and Losmandy rail make it a reliable partner for demanding sessions – whether in the garden or under dark mountain skies.

A telescope for visionaries

The William Optics Ultra-Cat 131 is more than just an APO refractor. It’s a statement: a statement of quality, of passion, and of a vision for the future of astrophotography. Anyone who owns such an instrument holds a piece of William Optics history in their hands—and an instrument that can inspire generations to come.