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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.
ZWO 2.5mm 170° All-Sky Lens - For 1/2" Sensors

ZWO 2.5mm 170° All-Sky Lens - For 1/2" Sensors

by ZWO
SKU ZWO-LENS-2-5
$22.00 - $22.00
$22.00
$22.00 - $22.00
$22.00
Price Match Policy!
  • 2.5mm Focal Length
  • 170° All-Sky Field of View
  • Designed for 1/2" Format Sensors
  • CS-Mount Thread
1 in stock
Qualifies for FREE Shipping in CONUS on orders over $350.
  • Description
  • FAQ
  • Specifications
  • In the Box
  • Downloads
  • Warranty

  • ZWO 2.5mm 170° All-Sky Lens - For 1/2" Sensors

    The ZWO 2.5mm 170° All-Sky CS Lens transforms your astronomy camera into a horizon-to-horizon sentinel, capturing a massive 170-degree field of view in a single frame. This 2.5mm focal length lens is engineered specifically for cameras with a 1/2" sensor, such as the ZWO ASI178 and ASI185 series, to monitor meteor showers, track atmospheric phenomena, or conduct sky surveillance.

    Achieve a 170° All-Sky Perspective

    The primary function of this 2.5mm lens is to deliver an immense 170° field of view. This expansive coverage allows you to capture the entire visible sky dome at once, making it the ideal tool for time-lapses of the Milky Way's transit, recording meteor showers like the Perseids or Geminids, or monitoring for transient events like fireballs and satellite flares.

    Optimized for 1/2" Format Sensors

    This lens is designed to match the imaging circle of 1/2" format sensors. When paired with cameras like the ZWO ASI178MM, ASI178MC, or ASI185MC, it produces a complete, circular all-sky image with minimal vignetting at the sensor's edges. This ensures that the data you collect from horizon to horizon is usable and consistent.

    • Direct Compatibility: Threads directly onto the CS-mount of compatible ZWO cameras.
    • Sensor Match: The 2.5mm focal length is calculated to project the full 170° field onto the smaller sensor format, preventing wasted field of view or excessive black borders.

    CS-Mount Connection and Considerations

    The lens features a standard CS-mount thread for direct attachment to many planetary and guide cameras. However, it's critical to note that if your camera has a C-mount thread, a C-to-CS mount adapter is required to achieve focus. This adapter is not included and must be sourced separately. This is a crucial distinction, as a C-mount camera without the adapter will not reach focus with this lens.

  • What cameras are compatible with the ZWO 2.5mm All-Sky Lens?

    This 2.5mm lens is specifically designed for cameras with a 1/2" sensor format and a CS-mount. It is an excellent match for models like the ZWO ASI178MM, ASI178MC, and ASI185MC. It will also work with the ASI120 series.

    Do I need any adapters to use the ZWO 2.5mm lens?

    It depends on your camera's mount. The lens has a CS-mount thread. If your camera (like the ASI178) has a native CS-mount, it will attach directly. If your camera uses a C-mount, you will need a C-to-CS mount adapter ring to achieve focus. This adapter is not included.

    Is the ZWO 2.5mm lens good for capturing the Geminids meteor shower?

    Yes, absolutely. Its 170° field of view makes it perfect for meteor showers. You can point the camera straight up and capture meteors appearing anywhere in the sky without having to aim, making it an ideal setup for automated meteor detection with software like SharpCap or FireCapture.

    Will this 2.5mm lens work with a larger sensor, like an APS-C camera?

    No, this lens is not recommended for sensors larger than 1/2". The image circle it projects is too small for larger sensors and will result in severe vignetting, showing only a small illuminated circle in the center of a large black frame.

    Can I use filters with the ZWO 170° All-Sky Lens?

    This lens does not have a standard filter thread on the front or rear element. It is designed for wide-field, unfiltered imaging of the night sky. Attempting to place a filter in the optical path would require a custom solution.

    How do I focus the ZWO 2.5mm lens?

    The lens has a manual focus ring. You will need to adjust it by hand to achieve sharp stars. It's best to perform this at night, viewing a live feed from the camera on a laptop screen and adjusting the focus until stars appear as tight points of light.

  • SKU ZWO-LENS-2.5
    Focal Length 2.5mm
    Field of View 170°
    Mount CS-Mount
    Recommended Sensor Format 1/2"
    Warranty 2 Years

    • 170º 2.5mm CS Lens

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  • ZWO 2-Year Limited Warranty