Explore Scientific 99% Reflective 3" Diagonal

A 3-inch dielectric-coated star diagonal that reflects 99% of incoming light, designed for telescopes with 3-inch focusers.

The first-surface dielectric coating reflects virtually all incoming light, delivering the brightest image your telescope can produce.

The double-taper insert barrel slides smoothly into 3-inch focusers and the wider taper section prevents the diagonal from accidentally falling free. A compression ring lock secures eyepieces. Includes a 2-inch adapter so you can use your existing 2-inch eyepiece collection, and dust covers to keep optics clean in storage.

Key Features

• 99% first-surface dielectric coating for maximum brightness
• Double-taper insert barrel for secure, smooth fit
• Compression ring eyepiece lock
• 2" adapter and dust covers included
• Weight: 2.0 lbs (0.90 kg)

Ideal For

• Large refractor owners — the ES ED152 and other 3"-focuser telescopes
• Deep-sky visual observers — 99% dielectric reflectivity for the brightest possible views
• 2" eyepiece users — included adapter means your existing eyepieces work immediately

Good to Know

• 1.25" eyepiece adapter is sold separately
• Designed for telescopes with a 3" focuser — will not fit standard 2" focuser drawtube