Best Telescope Diagonals of 2026

The SVBONY SV188P Dielectric Mirror Star Diagonal is designed for astronomical viewing with its super flat mirror and over 99% reflective surface. Its 1.25 inches nosepiece fits 1.25 inches telescopes and accepts standard 1.25in filters, eyepieces, Barlow lenses and other accessories with a 1.25in insert barrel. The 90 degree viewing angle provides a more comfortable viewing angle for observing objects overhead. Additionally, the diagonal corrects the upside down and left right reversed image, and its built-in brass ring and thumbscrew accessories avoid eyepiece rotation during adjustments without scratching your eyepieces barrels.

The Astromania Telescope Diagonal offers a 90° angle design that lets you enjoy comfortable viewing without straining your neck, whether you're observing stars or landscapes. Its Amici prism technology ensures you see images upright and correctly oriented, which is great for birdwatching or deep-sky viewing. The diagonal features premium multi-layer coatings that boost brightness and clarity, giving you sharper and clearer views compared to standard mirrors. Built with a sturdy aluminum barrel and impact-resistant housing, it’s designed to withstand harsh temperatures, making it a reliable choice for outdoor astronomy enthusiasts who want durability and excellent optical performance.

The SVBONY Diagonal Mirror enhances your telescope experience with its 1.25-inch diameter, making it compatible with standard telescopes and eyepieces. The aluminum construction ensures high light transmittance, delivering clearer and brighter images. Additionally, the brass compression ring protects against surface damage, allowing you to use your eyepiece without worry. With support for 1.25-inch filters, this diagonal mirror offers versatility for a range of observations, giving you more options for your stargazing adventures.

The SVBONY SV188P Diagonal offers excellent performance for your telescope viewing needs. It features a high-reflective dielectric coating that boosts brightness and clarity, meaning you get clearer and more vivid images of the night sky. The 2-inch size fits most telescopes and eyepieces and even supports 2-inch filters, giving you flexibility with your accessories. It also includes a converter so you can easily use 1.25-inch eyepieces and other telescope components. With a comfortable 90-degree viewing angle, you can observe the stars without straining your neck, and the upright image reduces the need for extra image correction after viewing. This diagonal is designed to make your stargazing more enjoyable and convenient.

The Celestron Erect Image Prism is a great accessory for your telescope, especially for daytime terrestrial viewing. With this 1.25” diagonal, you can enjoy right side up and left-to-right correct images when using refractors and Schmidt-Cassegrain telescopes. The prism easily inserts into 1.25” focusers or visual backs and accepts standard 1.25” eyepieces. This means you can use your existing eyepieces with this prism, saving you the hassle of purchasing additional accessories. Weighing just 136.08 grams, it is lightweight and won't add much bulk to your setup. The Celestron Erect Image Prism is a versatile and convenient tool that enhances your viewing experience and allows you to explore the world around you with your telescope.

The Celestron Star Diagonal enhances your telescope experience by providing clear and bright views. With its 90° viewing angle, you can observe comfortably for longer periods, particularly through refractor and cassegrain telescopes. The diagonal features 58 layers of dielectric coatings, ensuring that over 99% of the light collected reaches your eyepiece, resulting in stunning images. Additionally, the twist-lock mechanism secures your eyepiece in place, promoting better optical alignment and reducing any potential image distortion. This diagonal also includes a step-down adapter, making it compatible with both 2” and 1.25” eyepieces and accessories for added versatility.

The SVBONY 1.25 inches 90 Degree Dielectric Mirror Diagonal is a great addition to your refracting or catadioptric telescopes. Its 90% reflectivity flat mirror helps reduce light loss and provides a clear and sharp view. The diagonal has a standard 1.25 inches diameter and a 90-degree viewing angle, making it compatible with eyepieces and barlow lenses. The full metal body with a dust cover is durable and ensures a prolonged life.

The SVBONY Diagonal Mirror enhances your stargazing experience with its 45-degree correct-image prism, ensuring you see sharp, upright images without any left-right inversion. Its innovative design features a durable ABS plastic housing and precision-machined aluminum barrels, providing both strength and stability. The inclusion of a brass lock screw and compression rings allows for secure attachment, protecting your telescope from scratches and damage. Additionally, it supports 1.25-inch filters, giving you the flexibility to customize your observations for a more versatile viewing experience.

The Astromania 1.25" 90-Degree Diagonal Mirror is a useful accessory for refractor and Cassegrain telescopes, offering a comfortable viewing orientation as you observe from above. It features a filter thread for any 1.25" filter and accepts standard 1.25" eyepieces. The mirror has a protective coating to ensure a long life and a metal barrel that provides secure seating in the focuser. With its wide 90 degree angle, you can view a correct image from a refractor telescope stand and just look down with a comfortable angle.

The CELESTRON Twist Lock Diagonal is designed to improve your telescope viewing experience. It offers a convenient 90° angle, making it easier and more comfortable to observe celestial objects without straining your neck. The diagonal features advanced dielectric coatings with 58 layers, which reflect over 99% of the light, ensuring you get bright and clear views. Its diffraction-limited optics help deliver sharp images by minimizing distortions. Additionally, the twist-lock mechanism keeps your eyepiece securely centered, improving the alignment and overall image quality. This accessory is perfect for refractor and cassegrain telescopes, enhancing both comfort and performance.