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Until May 2nd, 2025, orders under US$800 will not incur any duties or taxes upon delivery. Please note that orders under US$800 crossing the Canada-USA border after this date will be subject to duties. They will be billed by the carrier, and you will be responsible to pay them. Prioritize ordering items that are in stock!
Until May 2nd, 2025, orders under US$800 will not incur any duties or taxes upon delivery. Please note that orders under US$800 crossing the Canada-USA border after this date will be subject to duties. They will be billed by the carrier, and you will be responsible to pay them. Prioritize ordering items that are in stock!

Features

  • Adjusts back-focus between your camera and telescope for the best astroimaging results
  • Kit includes 3 spacer rings of different lengths (7.5mm, 12mm, 30mm)
  • Threads to your T-Ring and T-Adapter with standard male and female T-Threads

Celestron M42 Spacer Kit

To achieve the best astroimages, it is important to attain the proper back-focus distance for your camera relative to the telescope it is being used with. If the back-focus distance your camera consumes is not exact, the performance at the corners of full frame imaging sensors will suffer—stars will appear elongated and not as pinpoints.
Example: RASA 8 with a ZWO ASI 183 MC PRO camera

  • Required back-focus distance for RASA 8 with included M42 camera adapter: 25mm
  • Back-focus consumed by ZWO ASI 183 MC PRO camera: 17.5mm
  • To achieve equal back-focus distance, a 7.5mm M42 spacer ring is required


Celestron’s M42 Spacer Ring kit includes three different length spacer rings to achieve the proper back-focus distance with our popular Celestron optical tubes and T-thread camera adapters.

How to Use
Depending your method of astrophotography (DSLR or CCD/CMOS), there are two ways to use the M42 Spacer Ring. If you are using a DSLR, place the desired M42 Spacer Ring between your T-Ring and your T-Adapter for your optical tube. If you are using a CCD or CMOS camera, place the desired M42 Spacer Ring between the camera and the T-Adapter for your optical tube.


Below is a quick guide to help you determine which spacer ring to use for our EdgeHD, Schmidt-Cassegrain, and RASA 8 optical tubes:

Spacer Ring Size: Works best with:
7.5mm Provides proper spacing with RASA 8 for many ZWO cameras
12mm Provides proper spacing with RASA 8 for many Atik cameras
30mm Converts ZWO camera w/filter slider to 55mm back-focus standard for use with Schmidt-Cassegrain & EdgeHD


Body
The M42 Spacer Rings are machined aluminum black anodized. The internal surfaces are blackened and glare-threaded to provide the highest contrast. Each spacer ring has a knurled surface, providing a great gripping surface for threading/unthreading. The M42 Spacer Rings are compatible with M42 x 0.75 (T-thread) camera adapters.

Specifications

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

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