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IMPORTANT: Our store is located in Canada. All orders that include products manufactured outside of Canada or USA will be subject to tariffs and duties, regardless of the order value. US customers are responsible for all applicable duties and tariffs, and those will be billed by the carrier, except for the Lacerta upgrade kit, for which we collect them at checkout.
IMPORTANT: Our store is located in Canada. All orders that include products manufactured outside of Canada or USA will be subject to tariffs and duties, regardless of the order value. US customers are responsible for all applicable duties and tariffs, and those will be billed by the carrier, except for the Lacerta upgrade kit, for which we collect them at checkout.
William Optics 99% Dielectric Dura Bright Diagonal - 1.25"
William Optics 99% Dielectric Dura Bright Diagonal - 1.25"
William Optics 99% Dielectric Dura Bright Diagonal - 1.25"
William Optics 99% Dielectric Dura Bright Diagonal - 1.25"

William Optics 99% Dielectric Dura Bright Diagonal - 1.25"

by William Optics
SKU WO-D-125D-C-DB
$138.00 - $138.00
$138.00
$138.00 - $138.00
$138.00
Price Match Policy!
  • 1.25" Barrel Diameter
  • 99% Dielectric Coated Mirror
  • 1/12λ Mirror Surface Accuracy
  • 12mm Thick Mirror Substrate
  • 100% Real Carbon Fiber Side Plates
1 in stock
Qualifies for FREE Shipping in CONUS on orders over $350.
  • Description
  • FAQ
  • Specifications
  • In the Box
  • Warranty

  • William Optics 99% Dielectric Dura Bright Diagonal - 1.25"

    The William Optics 1.25" Dura-Bright Diagonal delivers maximum image brightness and contrast through its 99% reflective dielectric coatings and a precision 1/12λ mirror. Built on a thermally stable 12mm thick substrate and housed in a patented, permanently aligned chassis with 100% real carbon fiber plates, this diagonal ensures your telescope's optical path remains perfect from the first day of use.

    The 1/12λ Mirror: 99% Reflectivity for Maximum Contrast

    A star diagonal is a critical element in the optical chain, and the Dura-Bright is built around a laboratory-grade mirror. The 12mm thick substrate provides exceptional thermal and mechanical stability, while the surface is polished to a 1/12λ wave accuracy, preserving the sharpness produced by your telescope's objective. Dielectric coatings provide 99% reflectivity, noticeably brightening the image and increasing contrast on faint deep-sky targets and subtle planetary details like the cloud bands of Jupiter.

    Patented Design: 100% Carbon Fiber and Permanent Alignment

    William Optics rejects the idea that a diagonal should ever need user adjustment. Where competing designs use collimation screws—an admission of potential mechanical flexure—the Dura-Bright employs a patented, fixed housing that guarantees perfect alignment for life. The 100% real carbon fiber side plates provide extreme rigidity and a touch of class, while internal baffles eliminate stray light for blacker backgrounds.

    • Compression Rings: Both the 1.25" eyepiece holder and adapter use brass compression rings to securely grip your eyepieces without marring their barrels.
    • Glove-Friendly Screws: Large, knurled thumbscrews are easy to operate even on cold nights while wearing gloves.
    • Internal Safety Stop: A machined stop prevents long 1.25" eyepiece barrels from ever making contact with the diagonal's mirror surface.

    Dura-Bright vs. Standard Diagonals: A 5% Gain in Reflectivity

    Compared to standard aluminum or silver diagonals that typically offer 90-94% reflectivity, the Dura-Bright's 99% dielectric mirror transmits significantly more light to your eye. This 5% or greater increase in light throughput makes a visible difference when observing at the limits of your telescope, rendering faint galaxies brighter and globular clusters more resolved. The dielectric coatings are also far more durable than standard coatings, ensuring this brightness advantage does not degrade over years of use and cleaning.

  • What is the benefit of the William Optics Dura-Bright Diagonal's 99% reflectivity?

    The 99% reflectivity from the dielectric coatings ensures the maximum amount of light from your telescope reaches the eyepiece. This results in brighter images and higher contrast compared to standard diagonals (which are often 90-94% reflective), making faint objects easier to see and planetary details more distinct.

    Will the 1.25" Dura-Bright Diagonal improve my views of Jupiter and Saturn?

    Yes. The combination of high reflectivity and the 1/12λ mirror surface preserves the finest details your telescope can resolve. This allows for sharper views of Jupiter’s Great Red Spot, subtle cloud bands, and the Cassini Division in Saturn’s rings, especially when compared to a lower-quality stock diagonal.

    Why doesn't the William Optics Dura-Bright Diagonal have collimation screws?

    William Optics considers adjustable alignment systems a sign of poor mechanical design. The Dura-Bright uses a patented, rigid, non-adjustable housing to guarantee perfect alignment from the factory that will not shift over time. This ensures consistent, optimal performance without the need for user adjustment.

    Is the carbon fiber on the Dura-Bright Diagonal just for aesthetics?

    While the 100% real carbon fiber side plates are visually striking, their primary purpose is structural. Carbon fiber is exceptionally strong, rigid, and lightweight, contributing to the diagonal's robust, permanently aligned construction.

    How do I use filters with the William Optics 1.25" Dura-Bright Diagonal?

    You attach standard 1.25" threaded filters directly to the barrel of your 1.25" eyepieces before inserting them into the diagonal. The diagonal itself does not have filter threads.

    How does the Dura-Bright Diagonal perform for splitting double stars like Albireo in my 80mm refractor?

    For a task like splitting the colorful components of Albireo (Beta Cygni), the Dura-Bright excels. Its high-precision 1/12λ mirror prevents any degradation of the star's Airy disk, ensuring the tightest possible stars. The high light transmission also helps maintain the brightness and rich color contrast of the binary pair in a smaller 80mm aperture.

  • Diagonal Size 1.25"
    Viewing Angle 90°
    Reflectivity 99%
    Mirror Coatings Dielectric
    Mirror Surface Accuracy 1/12λ
    Mirror Thickness 12mm
    Side Plate Material 100% Real Carbon Fiber
    Alignment Patented Non-Adjustable Design
    Eyepiece Holder Brass Compression Ring
    Baffling Internal Anti-Reflection Baffling
    Safety Feature Internal Stop for Eyepiece Barrels

    • 1.25" Dura Bright Dielectric Diagonal

      × 1

    • Dust Caps

      × 2

  • William Optics 2-Year Warranty