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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.
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"
SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"

SVBONY SV188P 90° Dielectric Mirror Diagonal - 2"

by SVBONY
SKU SV-F9171D
$63.00 - $63.00
$63.00
$63.00 - $63.00
$63.00
Price Match Policy!
  • 99% Reflectivity Dielectric Coatings
  • 90-Degree Viewing Angle
  • 11mm Thick Mirror Substrate
  • Durable Aluminum Alloy Body
  • Brass Compression Ring Eyepiece Holder
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Availability Info
Qualifies for FREE Shipping in CONUS on orders over $350.
  • Description
  • FAQ
  • Specifications
  • In the Box
  • Warranty

  • SVBONY SV188P 99% Reflectivity 90-Degree Dielectric Mirror Diagonal

    The SVBONY SV188P 90-Degree Dielectric Mirror Diagonal maximizes image brightness by delivering 99% reflectivity from its precision 11mm thick mirror. This design ensures that the absolute minimum amount of light is lost in the optical path, providing brighter, higher-contrast views through refractors and Cassegrain telescopes.

    99% Dielectric Mirror: Maximizing Light Throughput

    At the core of the SV188P is a mirror with advanced dielectric coatings that achieve 99% reflectivity. Unlike standard aluminum or silver coatings that can degrade over time, these multi-layer coatings are highly durable and deliver consistent light transmission across the visible spectrum. The mirror itself is 11mm thick, providing excellent thermal stability to maintain a precise figure during temperature changes.

    • 99% Reflectivity: Transmits nearly all collected light to your eyepiece, resulting in visibly brighter images compared to diagonals with lower-grade coatings.
    • Dielectric Coatings: Offer superior durability and resistance to aging, ensuring the diagonal maintains its peak optical clarity for years of use.
    • 11mm Thick Mirror: Provides a stable optical surface that resists warping from temperature fluctuations, preserving image sharpness.

    90-Degree Ergonomics and Eyepiece Protection

    Designed for comfortable observing, the 90-degree angle of the SV188P places the eyepiece in a natural position for viewing objects high in the sky, reducing neck strain during long sessions. The robust aluminum alloy body houses a non-marring brass compression ring, which secures your eyepieces firmly without scratching their barrels—a significant upgrade over simple set screw designs.

    • Comfortable Viewing Angle: The 90-degree bend is ideal for use with refractor and Cassegrain-style telescopes where the eyepiece would otherwise be at an awkward angle.
    • Brass Compression Ring: Grips the eyepiece barrel uniformly, preventing scratches and ensuring a secure, centered fit.
    • Aluminum Alloy Construction: Provides a rigid, durable frame for the optical components, ensuring reliable alignment.

    SV188P's 99% Reflectivity vs. Standard Silver Diagonals

    While a standard silver-coated diagonal typically offers 95-97% reflectivity, the SVBONY SV188P's 99% dielectric coatings provide a measurable increase in image brightness. This difference is most apparent when observing faint deep-sky objects or resolving low-contrast details on planets at high magnification.

    • Brighter Images: The 2-4% increase in light transmission can be the difference between spotting a faint galaxy arm or seeing only the core.
    • Enhanced Durability: Dielectric coatings do not tarnish or oxidize like silver, offering a longer operational life with consistent optical clarity.
    • Trade-off: The SV188P produces an image that is upright but mirror-reversed (left-to-right), making it perfect for astronomy but unsuitable for terrestrial viewing where correct image orientation is required.

  • Why is a 99% dielectric diagonal like the SVBONY SV188P better than a standard one?

    A 99% dielectric diagonal like the SVBONY SV188P transmits more of the light gathered by your telescope to the eyepiece. Standard diagonals can lose 5% or more of the light, but the SV188P loses only 1%. This results in brighter, higher-contrast images, which is especially critical for observing faint deep-sky objects like nebulae and galaxies.

    What is the image orientation through the SVBONY SV188P diagonal?

    The SVBONY SV188P provides an image that is upright but mirror-inverted (left and right are reversed). This is standard for astronomical mirror diagonals and is perfectly fine for observing celestial objects, as there is no "up" or "down" in space. However, it is not suitable for terrestrial viewing.

    How does the SVBONY SV188P's brass compression ring protect my eyepieces?

    Instead of a single set screw digging into your eyepiece barrel, the SVBONY SV188P uses a soft brass compression ring that tightens evenly around the barrel. This provides a secure grip without leaving scratches or gouges, preserving the condition of your valuable eyepieces.

    Will the SVBONY SV188P work with my refractor or SCT?

    Yes, the SV188P is designed specifically for telescopes that focus straight through the back, such as refractors, Schmidt-Cassegrains (SCTs), and Maksutov-Cassegrains. The 90-degree angle provides a much more comfortable viewing position than looking straight through.

    How will the SV188P's 99% reflectivity help when observing faint details on Jupiter with my 8" SCT?

    When observing planets like Jupiter, maximizing light throughput is key to seeing subtle, low-contrast features. The SVBONY SV188P's 99% reflectivity ensures that the faintest details in Jupiter's cloud bands and the Great Red Spot are delivered to your eye with maximum brightness and contrast, making them easier to resolve at high magnification.

    Is the SVBONY SV188P diagonal suitable for terrestrial viewing, like bird watching?

    No, the SVBONY SV188P is not recommended for terrestrial use. It produces a mirror-reversed image, meaning text would appear backwards. For correct image orientation for daytime viewing, you would need a 45-degree or 90-degree correct-image prism diagonal.

  • Brand SVBONY
    Material Aluminum Alloy
    Coatings Dielectric
    Reflectivity 99%
    Reflection Surface Dielectrically Coated
    Mirror Thickness 11mm
    Image Orientation Erect Image, Mirror Inverted
    Set Screws M4

    • SVBONY SV188P 2" Dielectric Diagonal

      × 1

    • Dust Caps

      × 2

  • SVBONY 1-Year Warranty