Alstar 1.25″ 45° Prism Diagonal Telescope

Description

Product Overview

The Alstar 1.25 inch 45 degree prism diagonal is engineered to provide superior image quality for both daytime terrestrial observation and night‑time astronomy. Unlike conventional mirror diagonals, this model uses a high‑precision optical prism that eliminates the slight distortion and loss of contrast often associated with reflective surfaces. Constructed from a robust metal barrel, the diagonal offers a secure fit in any 1.25 inch focuser and includes a threaded section for attaching standard 1.25 inch filters. Weighing only 3.2 ounces and measuring 4.4 x 2.1 x 2.8 inches, it is compact yet built to last, thanks to a protective coating on the prism that resists wear and environmental exposure.

Usage

Designed for versatile use, this diagonal excels in a variety of observing scenarios. Whether you are scanning the lunar surface, tracking deep‑sky objects, or conducting detailed terrestrial surveys of wildlife and landscapes, the prism delivers a bright, sharp image with accurate color rendition. Its ergonomic orientation allows comfortable viewing from above, reducing neck strain during extended sessions. The built‑in filter thread lets you add neutral density or light‑pollution filters, expanding its utility for astrophotography and high‑contrast daytime work.

Why Choose Us

Alstar’s reputation for precision optics is reflected in every component of this diagonal. The optical prism is fabricated from high‑index glass, providing superior light transmission compared to standard mirrors. The metal barrel is machined to tight tolerances, ensuring a snug, wobble‑free connection that maintains collimation. Each unit undergoes rigorous quality testing, including alignment checks and coating durability assessments, guaranteeing consistent performance over years of use. Our customer support team is available to assist with installation tips and filter recommendations, reinforcing the value of choosing a product backed by expertise and service.

Key Features

• Optical prism replaces mirror for clearer, sharper images
• 45° angle provides comfortable viewing orientation from above
• Metal barrel with protective coating ensures long‑term durability
• Standard 1.25 inch filter thread accommodates a range of accessories
• Lightweight, compact design fits most 1.25 inch telescope focusers

FAQ

Can this diagonal be used with Newtonian telescopes?

No, the design is intended for refractors, spotting scopes, and other telescopes that accept a 1.25 inch diagonal. Newtonian setups typically require a different mounting solution.

Is the prism coated for protection?

Yes, the prism features a multi‑layer anti‑reflective coating that protects against scratches and reduces light loss, extending the product’s lifespan.

What filters are compatible?

The built‑in 1.25 inch thread accepts any standard 1.25 inch filter, including neutral density, light‑pollution, and color correction filters.

How does the image quality compare to a mirror diagonal?

The prism delivers higher contrast and less chromatic aberration because it does not suffer from the slight surface imperfections that can affect mirrors, resulting in a brighter and more detailed view.

Is installation difficult?

Installation is straightforward: simply insert the diagonal into the focuser, tighten the set screw, and attach any desired filter. No additional tools are required.