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SVBONY SV135 7-21mm 52-36° Zoom Eyepiece - 1.25"

by SVBONY
SKU SV-W9105B
CA$38.00 - CA$38.00
CA$38.00
CA$38.00 - CA$38.00
CA$38.00
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  • 7mm to 21mm zoom focal length
  • 60° (at 21mm) to 40° (at 7mm) apparent field of view
  • Standard 1.25" barrel size
  • 13mm - 15mm of eye relief
  • Fully multi-coated optics for high contrast
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  • Description
  • FAQ
  • Specifications
  • In the Box
  • Warranty

  • Svbony SV135 1.25" 7-21mm Zoom Eyepiece

    The Svbony SV135 1.25" 7-21mm Zoom Eyepiece replaces a whole set of fixed eyepieces, offering a continuous focal length range from 7mm to 21mm with a simple twist. Its 7-element, 4-group optical design is fully multi-coated, delivering a 60° field of view at its widest setting. With 13mm to 15mm of eye relief and a weight of just 145g, it provides a versatile and comfortable viewing experience for planetary and lunar observation.

    The 7-21mm Zoom Range: Instant Magnification Adjustment

    The core advantage of the SV135 is its ability to change magnification without swapping eyepieces. You can start at the 21mm setting for a wide, low-power view to easily locate an object like Saturn, then simply twist the barrel to zoom in to 7mm for a high-power, detailed view of the rings—all without ever taking your eye from the telescope or losing the object from the field.

    60°-40° Field of View and Fully Multi-Coated Optics

    The SV135's 7-element optical system is fully multi-coated to maximize light transmission and contrast, which is critical for discerning faint details on Jupiter's cloud bands or resolving stars in tight clusters. The apparent field of view varies with magnification, from a wide 60° at 21mm to a more focused 40° at 7mm. This is a necessary trade-off in a zoom design, prioritizing magnification power at the high end.

    Ergonomics for Viewing: 15mm Eye Relief and 1.25" Filter Threads

    With an eye relief range of 13mm to 15mm, the SV135 is comfortable for most observers, including those who wear glasses. A twist-up rubber eye guard helps block stray light and maintain proper eye positioning. The standard 1.25" barrel is compatible with virtually any telescope, and the M28.5*0.6 threads allow you to attach standard 1.25" filters, like a moon filter for reducing glare.

    SV135 Zoom vs. Fixed Focal Length Eyepieces: The Convenience Trade-Off

    While a set of individual Plössl eyepieces might offer a wider, flatter field at each specific focal length, the SV135 zoom offers unparalleled convenience. It is an ideal solution for public outreach, travel scopes, or for observers who want to quickly find the optimal magnification for changing atmospheric conditions without carrying a case full of accessories.

    • Advantage of the SV135: One eyepiece covers a wide range of magnifications, is cost-effective, and simplifies your observing kit.
    • Advantage of Fixed Eyepieces: Typically provide a wider apparent field of view and potentially sharper edge-of-field correction compared to a zoom at the same focal length.

  • What is the main advantage of the Svbony SV135 zoom eyepiece?

    The primary advantage of the Svbony SV135 is convenience. It allows you to change magnification from a low-power 21mm to a high-power 7mm with a simple twist, eliminating the need to swap between multiple fixed-focal-length eyepieces. This is ideal for tracking objects or finding the perfect magnification for current seeing conditions.

    How does the field of view of the SV135 change when I zoom?

    The apparent field of view (AFOV) on the SV135 is variable. It is at its widest, 60°, at the 21mm setting. As you increase magnification by twisting towards the 7mm setting, the field of view narrows to 40°. This is a common characteristic of zoom eyepiece designs.

    Is the 13-15mm eye relief on the SV135 comfortable for eyeglass wearers?

    Yes, the 13mm - 15mm eye relief is generally sufficient for most eyeglass wearers to see the majority of the field of view comfortably. The adjustable rubber eye guard also helps in finding the optimal viewing distance from the lens.

    How would I use the SV135 zoom eyepiece to observe Jupiter with an 8" f/10 SCT?

    With an 8" f/10 SCT (2032mm focal length), you would start with the Svbony SV135 at the 21mm setting to get a wide, low-power view (97x magnification) to easily find and center Jupiter. Once centered, you can smoothly twist the eyepiece towards 7mm, increasing the magnification up to 290x to see details like the Great Red Spot and individual cloud bands, stopping at the point where the image is sharpest based on atmospheric conditions.

    Can the SV135 eyepiece show the entire Pleiades (M45) cluster in a small refractor?

    It depends on the refractor's focal length. The Pleiades (M45) is a very large cluster, requiring a wide true field of view. At its 21mm setting with a 60° apparent field, the SV135 may frame the cluster in a short focal length refractor (e.g., 400-500mm). However, in longer focal length telescopes, a fixed eyepiece with a wider field stop, like a 32mm Plössl, would be better suited for viewing the entire cluster at once.

    Can I use standard 1.25" filters with the Svbony SV135?

    Yes. The barrel of the Svbony SV135 is threaded with the standard M28.5*0.6 pitch, making it compatible with all standard 1.25" astronomy filters, such as moon filters, color filters for planets, or light pollution filters.

  • SKU W9105D
    Focal Length 7mm - 21mm
    Apparent Field of View 60° - 40°
    Barrel Size 1.25"
    Eye Relief 13mm - 15mm
    Lens Design 7 elements in 4 groups
    Lens Coating Fully Multi-Coated Green
    Zoom Type Linear
    Filter Threads M28.5*0.6
    Rubber Eye Guard Yes
    Material Metal + Optical Glass
    Color Black
    Net Weight 145g
    Package Dimensions 110 x 80 x 70mm
  • Svbony 1-Year Warranty