iOptron 1.25" Dielectic Star Diagonal

The iOptron 1.25" dielectric star diagonal is an excellent upgrade for any refractor or catadioptric telescope that accepts standard 1.25" accessories. Featuring multi-layer dielectric mirror coatings, this diagonal delivers high reflectivity (up to 99%), sharper contrast, and excellent color fidelity across the entire visible spectrum.

Whether you're observing planets, double stars, or deep-sky objects, this diagonal helps your telescope deliver the clean, bright images it’s capable of—without distortion or degradation.

High Reflectivity Dielectric Mirror

At the heart of this diagonal is a precision-polished mirror coated with multiple dielectric layers. Unlike aluminum or silver coatings that degrade over time, dielectric coatings are extremely hard and durable, offering years of consistent performance without tarnishing or scratching.

The result? More light to your eye, higher contrast, and sharper detail—especially helpful when observing subtle features on the Moon, Jupiter, or Saturn.

CNC Machined Body and Compression Ring Design

The diagonal housing is made from CNC-machined aluminum, with a black anodized finish that’s both durable and lightweight. The 1.25" eyepiece holder uses a brass compression ring, which gently grips your eyepiece barrel without marring or scratching the surface.

The 1.25" nosepiece also includes a removable barrel with standard filter threads, allowing you to use your favorite color or light pollution filters without modifying your diagonal setup.

Great for Visual Use with Refractors and SCTs

This diagonal is a perfect visual companion for any telescope with a 1.25" focuser or visual back, including:

• Refractors with 1.25" focusers

• Schmidt-Cassegrain telescopes using a 1.25" visual back

• Maksutov-Cassegrains

• Short-tube and spotting-style scopes with 90° viewing needs

It provides a 90° viewing angle, ideal for high-altitude targets or comfortable seated observing.

Included Accessories

• 1.25" dielectric mirror star diagonal

• Dust caps for nosepiece and eyepiece holder

• Brass compression ring

• Filter-threaded nosepiece

• Boxed packaging

Final Thoughts

The iOptron 1.25" dielectric star diagonal is a dependable optical upgrade for astronomers who want better image brightness, improved contrast, and long-lasting durability. It’s a practical enhancement over stock prism or lower-end mirror diagonals, and it’s built to handle years of regular observing.

Whether you're chasing planetary detail or scanning open clusters, this diagonal helps your scope reach its full visual potential.

Observing Tip:
For best performance, pair your dielectric diagonal with fully multi-coated eyepieces. You’ll maximize throughput, improve contrast, and get the most from your telescope’s aperture.