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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.
SVBONY SV221 45° Correct Image Prism Diagonal - 1.25"
SVBONY SV221 45° Correct Image Prism Diagonal - 1.25"
SVBONY SV221 45° Correct Image Prism Diagonal - 1.25"
SVBONY SV221 45° Correct Image Prism Diagonal - 1.25"
SVBONY SV221 45° Correct Image Prism Diagonal - 1.25"
SVBONY SV221 45° Correct Image Prism Diagonal - 1.25"
SVBONY SV221 45° Correct Image Prism Diagonal - 1.25"
SVBONY SV221 45° Correct Image Prism Diagonal - 1.25"
SVBONY SV221 45° Correct Image Prism Diagonal - 1.25"
SVBONY SV221 45° Correct Image Prism Diagonal - 1.25"
SVBONY SV221 45° Correct Image Prism Diagonal - 1.25"
SVBONY SV221 45° Correct Image Prism Diagonal - 1.25"
SVBONY SV221 45° Correct Image Prism Diagonal - 1.25"
SVBONY SV221 45° Correct Image Prism Diagonal - 1.25"

SVBONY SV221 45° Correct Image Prism Diagonal - 1.25"

par SVBONY
UGC SV-W9178B
$17.59 - $17.59
$17.59
$17.59 - $17.59
$17.59
Égalisation de prix!
  • Produces a fully erect, non-reversed image
  • Comfortable 45° viewing angle for terrestrial observation
  • Standard 1.25" barrel fits most refractor telescopes
  • Features a 19mm clear aperture
  • Threaded (M28.5x0.6) to accept 1.25" filters
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Info disponibilité
Admissible à la livraison GRATUITE aux USA pour les commandes de plus de 350$.
  • Description
  • FAQ
  • Specifications
  • In the Box
  • Warranty

  • SVBONY SV221 45-Degree Erecting Prism Diagonal for Refractor Telescope

    The SVBONY SV221 converts your refractor for terrestrial viewing, delivering a fully erect, non-reversed image at a comfortable 45° angle. It fits standard 1.25 inch focusers, features a 19mm clear aperture for bright views, and adds approximately 86mm of optical length to your light path. Weighing only 79g, this multi-coated prism diagonal is threaded for M28.5x0.6 filters, making it a lightweight and versatile addition to your kit.

    Correct-Image Views at a Comfortable 45° Angle

    The primary function of the SV221 is to correct the inverted and reversed image produced by a refractor telescope. Its internal prism system delivers an erect, non-reversed view, just as you see with your naked eye, making it intuitive to track moving subjects like birds, ships, or wildlife. The 45° deflection provides a much more comfortable viewing posture for daytime observation compared to looking straight through the telescope.

    The multi-coated prism and 19mm clear aperture ensure that the image remains bright and clear. This makes the SV221 an essential accessory for transforming your astronomical refractor into a powerful, long-range spotting scope for terrestrial use.

    Secure Clamping and 1.25" Filter Compatibility

    The SV221 is constructed with a durable, precision-molded plastic main body and machined aluminum barrels for a secure fit. Unlike basic diagonals that use a single screw to hold the eyepiece, this model features a brass compression ring that provides a firm, even grip without scratching or marring your eyepiece barrels. This secure connection maintains optical alignment and protects your equipment.

    For added versatility, the 1.25" nosepiece is threaded for standard M28.5x0.6 filters. You can easily attach a moon filter, a light pollution filter, or colored planetary filters to enhance your views without needing a separate filter cell.

    SV221 Erecting Prism vs. a Standard Mirror Diagonal

    It's important to choose the right diagonal for your purpose. While both redirect light for comfortable viewing, they produce very different images.

    • Standard Mirror Diagonal: A typical "star diagonal" uses a mirror to bend the light path. This produces an image that is upright but reversed left-to-right. This is perfectly acceptable for astronomy, as stars are points of light, but it can be disorienting for terrestrial viewing where "left is left" matters.
    • SVBONY SV221 Erecting Prism: This diagonal uses a prism to provide a fully corrected image—upright and not reversed. This is the ideal choice for daytime, terrestrial observation with a refractor or Maksutov-Cassegrain, as it makes panning and tracking objects natural and intuitive.

  • Why do I need the SVBONY SV221 for daytime viewing with my refractor?

    A refractor telescope naturally produces an image that is upside-down and backward. The SVBONY SV221 uses a 45° prism to correct this, delivering an erect and non-reversed image. This makes it possible to use your astronomy telescope as a high-power spotting scope for activities like birdwatching or landscape viewing.

    Will the SVBONY SV221 work with my Newtonian telescope?

    No. The SVBONY SV221 is designed for refractor and Cassegrain-type telescopes. A Newtonian reflector does not have enough focuser travel to reach focus with the additional 86mm optical length of a prism diagonal. Newtonians require very low-profile focusers and do not typically use diagonals in the same way.

    Can I use 1.25" filters with the SVBONY SV221 diagonal?

    Yes. The 1.25" barrel of the SV221 has standard M28.5x0.6 filter threads. This allows you to attach any standard 1.25" filter, such as a moon filter for reducing glare or a light pollution filter for enhancing contrast on celestial objects.

    What is the advantage of the SVBONY SV221's clamping system?

    The SV221 features a brass compression ring inside the eyepiece holder. When you tighten the screw, this ring tightens evenly around the eyepiece barrel. This is superior to a simple screw which can scratch or dent your eyepieces and potentially cause a slight tilt.

    Is the SVBONY SV221 suitable for high-magnification planetary viewing?

    While the SVBONY SV221 can be used for astronomy, it is primarily optimized for lower-power terrestrial viewing. Prism diagonals can sometimes introduce a small amount of chromatic aberration (false color) at very high magnifications. For critical, high-power observation of planets like Jupiter or Saturn, a high-quality mirror diagonal is often preferred by discerning astronomers.

    How does the 45° angle of the SV221 affect observing?

    The 45° angle is ideal for terrestrial viewing, as you are typically looking at objects at or near the horizon. This provides a comfortable, natural neck position. For astronomical viewing, a 90° diagonal is often preferred, as it makes it easier to view objects that are high overhead, near the zenith.

  • Brand SVBONY
    Model SV221
    Optical Design Prism Diagonal
    Barrel Size 1.25 inch
    Deflection Angle 45°
    Image Orientation Erect image, non-reversed
    Clear Aperture 19mm
    Coatings Multi-Coated (MC)
    Eyepiece Connection 1.25" Clamp with Screw
    Filter Threads M28.5x0.6
    Optical Length appr. 86mm
    Material Plastic & Metal
    Net Weight 79g / 2.78oz

    • SV221 1.25" 45 Degree Correct Image Prism Diagonal

      × 1

    • M3 Screws

      × 3

    • Dust Cap

      × 1

    • Dust Plug

      × 1

  • SVBONY Warranty Policy