Description
Product Overview
The A ALSTAR 90 Degree Erecting Prism is engineered for users who demand a true‑upright image from their optical instruments. Unlike traditional mirror diagonals, this prism utilizes optically processed BK7 glass, ensuring minimal light loss and superior image clarity. The housing combines a lightweight ABS plastic body with metal barrels for a rigid, vibration‑free connection, while an aluminum clamping screw secures the eyepiece firmly in place. Dimensions measure 4.4 x 2.1 x 2.8 inches and the unit weighs only 4.6 ounces, making it easy to mount on any 1.25″ telescope or spotting scope. A built‑in dust cap and plug protect the optics when not in use, extending the product’s lifespan.
Usage
Designed for both daytime terrestrial observation and nighttime astronomy, this erecting prism excels in a variety of environments. Birdwatchers can enjoy a correctly oriented view of wildlife without the need to mentally flip the image, while hikers and nature photographers benefit from the left‑right correction when scanning landscapes. Astronomers appreciate the clear, sharp view of celestial objects, especially when paired with a 1.25″ filter for light‑pollution reduction. The prism’s universal 1.25″ eyepiece thread makes it compatible with most standard accessories, allowing seamless integration into existing setups.
Why Choose Us
A ALSTAR stands out for its commitment to optical excellence and durable construction. The use of BK7 glass—a high‑index material prized for its low dispersion—delivers true‑color fidelity and sharp contrast, outperforming many mirror‑based alternatives that can introduce distortion. Each prism undergoes rigorous quality testing to ensure precise 90‑degree light deviation and a secure fit that resists loosening during transport. The inclusion of a dust cap and plug demonstrates attention to long‑term maintenance, a feature often omitted by competitors. With a proven best‑seller rank of #16 in Telescope Diagonals, this product has earned the trust of the astronomy community.
Key Features
- Premium BK7 glass prism for high‑definition, distortion‑free images
- 90‑degree erecting design provides upright, left‑right corrected view
- ABS housing with metal barrels and aluminum clamping screw ensures a solid, vibration‑free fit
- Standard 1.25″ eyepiece and filter thread compatibility for versatile accessory use
- Dust cap and plug included to protect optics and extend product life
FAQ
Can this prism be used with any 1.25 inch eyepiece?
Yes, the prism features a universal 1.25″ thread that fits the vast majority of telescope and spotting scope eyepieces on the market.
Will the erecting prism affect image brightness?
Because it is made from BK7 glass rather than a reflective mirror, light transmission loss is minimal, preserving brightness and contrast for both daytime and night‑time viewing.
Is the prism suitable for astrophotography?
The prism provides a correctly oriented image, which can be advantageous for visual observation, but for long‑exposure astrophotography many users prefer a standard diagonal to avoid additional glass surfaces that may introduce slight chromatic aberration.
How do I protect the prism when not in use?
Use the supplied dust cap to cover the front surface and the dust plug for the rear thread. This prevents dust and moisture from entering the optical path.
What is the warranty on this product?
A ALSTAR offers a one‑year limited warranty covering manufacturing defects. Register your purchase on the official website to activate warranty support.
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