William Optics Ultra-Cat 131 WFID APO Petzval OTA | L-UC131 NEAF2026 Identical filter thickness to existing

Identical filter thickness to existing standards and double-sided fine polishing

That means you can get more out of every observing session

the peripheral light reduction control is excellent

but the story does not end there

Use the iOptron 90° Dielectric Star Diagonal to place your head in a comfortable viewing position when your refractor or catadioptric optical tube assembly (OTA) is aimed at or near the zenith

William Optics Ultra-Cat 131 WFID APO Petzval OTA | L-UC131 NEAF2026 Identical filter thickness to existingThe 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,