Ultra-Cat 108 R

The William Optics Ultra-Cat 108 R is a refined 108mm apochromatic astrograph designed for astrophotographers who need wide-field performance with greater rear-end mechanical stability. Built on the proven 5-element advanced Petzval optical platform of the Ultra-Cat 108, it keeps the fast f/4.8 focal ratio, 60mm image circle, and WIFD internal focusing system while introducing the updated STX-R rear interface. The STX-R structure reverses the original rear mechanical layout to improve support for heavier modern imaging trains, helping reduce the chance of rear-end sag when using cooled cameras, filter wheels, off-axis guiders, or longer accessory stacks. With its flat-field Petzval optics, stable internal focusing, and refined rear-end support, the Ultra-Cat 108 R is built for demanding deep-sky imaging with full-frame and medium-format camera systems. Key Features: Advanced 5-Element Petzval Design Provides a naturally flat image field without requiring an additional field flattener, delivering sharp stars and clean detail across a wide imaging area. 60mm Superior Image Circle Supports full-frame and medium-format camera systems, giving astrophotographers more freedom for wide-field composition and high-resolution deep-sky imaging. F/4.8 Fast Optics Captures deep-sky objects efficiently with a bright optical system designed for rich nebulae, galaxies, and expansive celestial structures. WIFD (William Optics Internal Focuser Design) The patented internal focusing system keeps the focusing mechanism centered inside the telescope, improving balance and helping avoid rear drawtube-related flexure or vignetting. STX-R Rear Tilt Interface An evolved STX structure with a reversed rear mechanical layout, designed to improve support for heavier imaging setups and reduce the chance of rear-end sag while retaining convenient tilt adjustment capability. Anti-Shrink Lens Cell Technology Helps maintain stable optical alignment under changing temperatures by minimizing the effects of material expansion and contraction around the lens cell. Built-In Patented Bahtinov Mask Integrated into the front cap for quick and accurate focusing, making precise star focus easier in the field. Patented Handle Bar Design Improves handling, portability, and accessory mounting while maintaining the clean mechanical layout of the Ultra-Cat platform. Personalized Laser Engraving Available for direct purchases, allowing each telescope to carry a customized personal mark.