The William Optics 1.25" 90° erecting prism diagonal D-EP90-125-RC61 (SKU: D-EP90-125-RC61) is a high-quality correcting-image diagonal designed exclusively for the William Optics RedCat 61 III WIFD telescope. The BaK4 prism with anti-reflection coatings provides a correctly oriented image (up is up, left is left), making the diagonal ideal for daytime and terrestrial observing. The interior is matte-blackened and threaded to minimize stray light, while the CNC-machined 6061T aluminium housing ensures durability and precision. Depending on production batch, the plate may be anodized in black or red.

Key features

• 90° erecting prism diagonal for correct-image viewing
• dedicated to the William Optics RedCat 61 III WIFD telescope
• BaK4 prism with anti-reflection coatings for high contrast and transmission
• standard 1.25" telescope and eyepiece interface
• CNC-machined 6061T aluminium body with threaded matte-black interior
• excellent for daytime and terrestrial observing
• note: limited backfocus – not all 1.25" eyepieces may reach focus
• manufactured in Taiwan; 2-year William Optics warranty
• not compatible with earlier RedCat 61 versions or with RedCat 71

Included items

• William Optics 1.25" 90° erecting prism diagonal D-EP90-125-RC61

Technical specifications

• manufacturer: William Optics
• model: D-EP90-125-RC61
• diagonal type: erecting prism diagonal
• angle: 90°
• telescope side: 1.25" barrel
• eyepiece side: 1.25" barrel
• prism material: BaK4 optical glass
• optical coatings: anti-reflection coated
• internal finish: matte-blackened and threaded
• housing material: CNC-machined 6061T aluminium
• intended use: daytime and terrestrial observing with RedCat 61 III WIFD
• compatibility: RedCat 61 III WIFD only
• not compatible with: earlier RedCat 61 models, RedCat 71
• country of manufacture: Taiwan
• warranty period: 2 years