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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.
Celestron M42 Spacer Kit
Celestron M42 Spacer Kit
Celestron M42 Spacer Kit
Celestron M42 Spacer Kit
Celestron M42 Spacer Kit
Celestron M42 Spacer Kit

Celestron M42 Spacer Kit

by Celestron
SKU CEL-93618
$47.95 - $47.95
$47.95
$47.95 - $47.95
$47.95
Price Match Policy!
  • Includes three M42 x 0.75 spacer rings: 7.5mm, 12mm, and 30mm
  • Achieve precise back-focus for various telescope and camera combinations
  • Black anodized aluminum construction with glare-threaded interiors for maximum contrast
  • Knurled grip surface for easy, secure installation
  • Each ring is clearly labeled with its length for quick identification
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  • Description
  • FAQ
  • Specifications
  • In the Box
  • Downloads
  • Warranty

  • Celestron M42 Spacer Kit

    The Celestron M42 Spacer Kit provides three essential lengths—7.5mm, 12mm, and 30mm—to precisely achieve the correct back-focus for your imaging system. These rings use the standard M42 x 0.75 T-thread, ensuring compatibility with a wide range of cameras and telescope T-adapters. By inserting the correct spacer, you eliminate the elongated stars at the edge of the frame that result from incorrect spacing, ensuring your images are sharp across the entire sensor.

    Back-Focus Correction: Achieving Pinpoint Stars with 7.5mm, 12mm, and 30mm Spacers

    Attaining the exact back-focus distance specified by your telescope's optical design is critical for astrophotography. This kit simplifies the process by providing three of the most commonly needed spacer lengths. For example, a RASA 8 requires a 25mm back-focus; if your ZWO camera consumes 17.5mm, the 7.5mm ring in this kit provides the perfect solution to achieve sharp, pinpoint stars across the field.

    • 7.5mm Spacer: Ideal for matching many popular ZWO cameras to the required back-focus on a RASA 8 astrograph.
    • 12mm Spacer: Provides the correct spacing for many Atik cameras when used with a RASA 8.
    • 30mm Spacer: Converts ZWO cameras equipped with a filter slider to the 55mm back-focus standard, making them perfectly spaced for Schmidt-Cassegrain and EdgeHD telescopes.

    Physical Design: Machined Aluminum with High-Contrast M42 x 0.75 Threads

    Each ring in the Celestron M42 Spacer Kit is machined from black anodized aluminum for durability and a precise fit. The interior surfaces are blackened and glare-threaded, a critical feature that prevents stray light from reflecting off internal surfaces and reducing the contrast of your images. The exterior features a knurled grip surface, allowing you to easily and securely thread and unthread the spacers, even when wearing gloves in the dark.

  • How do I know which M42 Spacer Kit ring to use for my RASA 8 and ZWO camera?

    First, find the required back-focus for the RASA 8 with its M42 adapter, which is 25mm. Then, find the back-focus of your ZWO camera (for example, 17.5mm). Subtract the camera's back-focus from the required back-focus (25mm - 17.5mm = 7.5mm). You would need the 7.5mm spacer ring from the kit to achieve perfect spacing.

    Which spacer from the M42 Spacer Kit do I need for my EdgeHD 8" and a ZWO camera with a filter slider?

    To use a camera with a Schmidt-Cassegrain or EdgeHD telescope, you typically need to meet the 55mm back-focus standard. The 30mm spacer ring is specifically designed to be combined with ZWO cameras and their filter sliders to achieve this 55mm distance, ensuring a fully illuminated and corrected field.

    What does "M42 x 0.75" thread mean for the M42 Spacer Kit?

    M42 x 0.75 refers to the thread specification. "M42" means it is a metric thread with a 42mm diameter, and "0.75" is the thread pitch in millimeters. This is the universal standard for "T-threads" or "T-mounts" in astronomy, ensuring these spacer rings will be compatible with the vast majority of telescope T-adapters, T-rings, and astrophotography cameras.

    Are the rings in the M42 Spacer Kit labeled?

    Yes, each of the three rings (7.5mm, 12mm, and 30mm) is labeled with its length. This makes it easy to identify the correct spacer you need for your setup without having to measure them each time.

    What is the purpose of the glare-threaded interior on these spacers?

    The blackened and glare-threaded interior surfaces are designed to trap and absorb any off-axis stray light that enters the optical train. This prevents internal reflections that can lower image contrast, wash out faint details, and introduce artifacts into your astrophotos. It's a critical feature for high-contrast imaging.

    How do I install a spacer from the M42 Spacer Kit with a DSLR camera?

    For a DSLR, you will typically have a T-Ring that attaches to your camera body and a T-Adapter that slides into the telescope's focuser. You would place the required M42 spacer ring between the T-Ring and the T-Adapter to add the necessary distance.

  • Thread M42 x 0.75
    Spacer Lengths 7.5mm (.29"), 12mm (.47"), and 30mm (1.18")
    Construction Aluminum, black anodized
    Interior Finish Blackened and glare threaded
    Exterior Finish Knurled grip surface, labeled with length

    • 7.5mm M42 Spacer Ring

      × 1

    • 12mm M42 Spacer Ring

      × 1

    • 30mm M42 Spacer Ring

      × 1

  • Celestron 2-Year Warranty