Skip to content
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.
ZWO AR Protective Window

ZWO AR Protective Window

by ZWO
SKU ZWO-D21AR
$15.00 - $39.00
$15.00
$15.00 - $39.00
$15.00
Price Match Policy!
  • Protects camera sensor from dust and humidity
  • 21mm diameter for specific ZWO camera models
  • High-transmission Anti-Reflection (AR) coatings
  • 1/4λ surface flatness prevents image degradation
  • 1.1mm thickness ensures no change to back focus
Backordered
Request Stock Alert
Availability Info
Qualifies for FREE Shipping in CONUS on orders over $350.
  • Description
  • FAQ
  • Specifications
  • In the Box
  • Warranty

  • ZWO D21 AR Protective Window

    The ZWO D21 AR Window provides essential sensor protection with an optically precise 1/4λ surface flatness to maintain image sharpness. Its 21mm diameter and slim 1.1mm thickness ensure a perfect fit in compatible ZWO cameras, using high-transmission anti-reflection coatings to shield the sensor from dust and moisture without altering the optical path.

    Transparent Protection at 1/4λ Flatness

    This window serves as a clear, protective barrier between your camera's delicate sensor and the outside environment. The 1/4λ surface flatness specification guarantees the window is optically parallel, preventing it from introducing any distortion, astigmatism, or other aberrations into your images. It is an insurance policy for your sensor that has no detectable impact on optical quality.

    Seamless Fit with a 21mm Diameter

    Designed as a direct replacement or protective addition, the 21mm diameter window fits a wide range of popular ZWO cameras, including the ASI120, ASI224, ASI290, ASI178, and ASI385 series. This precise sizing ensures it seats correctly within the camera body, providing a complete seal against contaminants.

    Minimal Optical Impact at 1.1mm Thickness

    At just 1.1mm thick and featuring anti-reflection (AR) coatings on both surfaces, this window is engineered to be nearly invisible to your telescope's light path. The AR coatings maximize light transmission and eliminate ghosting from bright stars. The 1.1mm thickness matches original factory windows, ensuring you maintain the correct back focus without needing additional spacers or adjustments.

  • What is the primary purpose of the ZWO D21 AR Window?

    It acts as a protective cover for your camera's sensor. It shields the delicate sensor from dust, humidity, and potential physical contact without degrading image quality, thanks to its 1/4λ flatness and AR coatings.

    Which ZWO cameras use the D21 AR Window?

    The D21 AR window is compatible with several ZWO cameras, including the ASI120MM/MM-S, ASI224MC, ASI385MC, ASI290MC/MM, ASI290MINI, ASI178MM, and ASI120MINI models. Always confirm your specific camera model before purchasing.

    Will installing the D21 AR Window change my focus point?

    No. With a thickness of just 1.1mm, it is designed to be optically neutral and match the original window in compatible cameras. Your focus point and back focus should remain unchanged.

    How do I install the ZWO D21 AR Window on my ASI290MM Mini?

    Installation involves carefully unscrewing the front nosepiece of the camera to access the sensor chamber. The old window (if present) can be gently removed, and the new D21 AR window is dropped into its place. Ensure the environment is as dust-free as possible during the process.

    Can I use the D21 AR Window instead of a UV/IR cut filter for planetary imaging with my ASI224MC?

    No, this is not a filter. The D21 is an AR-coated clear window designed for protection and maximum light transmission. For planetary imaging with a color camera like the ASI224MC, you still need a separate UV/IR Cut (Luminance) filter to ensure correct color balance and sharpness, as the sensor is sensitive to out-of-band light.

    How should I clean the ZWO D21 AR Window?

    Treat it like any high-quality optic. First, use a clean air blower to remove any loose dust. For fingerprints or smudges, use a microfiber cloth with a small amount of a dedicated optical cleaning solution. Wipe gently in a circular motion from the center outwards to avoid scratching the AR coatings.

  • SKU ZWO-D21AR1
    Diameter 21 mm
    Thickness 1.1 mm
    Surface Flatness 1/4 λ
    Type AR Coated Protective Window

    • D21 AR Window

      × 1

  • ZWO 2-Year Warranty