The Celestron M42 Spacer Ring Kit adjusts the back-focus between your camera and telescope for the best astroimaging results. The kit includes 3 spacer rings of different lengths (7.5mm, 12mm, 30mm) and threads to your T-Ring and T-Adapter with standard male and female T-Threads
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.
An example is the Celestron RASA 8 with a ZWO ASI 183 MC PRO camera. The required back-focus distance for the RASA 8 with included M42 camera adapter is 25mm. The back-focus consumed by the ZWO ASI 183 MC PRO camera is 17.5mm. So, to achieve equal back-focus distance, a 7.5mm M42 spacer ring is required.
The Celestron 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.
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. the desired M42 Spacer Ring between the camera and the T-Adapter for your optical tube.
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.
Here is a quick guide to help you determine which spacer ring to use for The Celestron 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
You can learn more about the Celestron M42 Spacer Ring Kit at Celestron’s website.
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