Optimize your astroimaging setup with the Celestron M42 Spacer Ring Kit, designed to precisely adjust the back-focus distance between your camera and telescope. This kit is essential for achieving the best possible astroimages, especially when dealing with full-frame sensors where improper back-focus can lead to elongated stars at the image corners. The kit includes three spacer rings of varying lengths (7.5mm, 12mm, 30mm), each crafted to fit standard male and female T-Threads commonly found on T-Rings and T-Adapters.

For example, using a RASA 8 telescope with a ZWO ASI 183 MC PRO camera requires a specific back-focus distance. The RASA 8, with its included M42 camera adapter, has a required back-focus distance of 25mm, while the ZWO ASI 183 MC PRO camera consumes 17.5mm of back-focus. To achieve the correct back-focus distance in this scenario, a 7.5mm M42 spacer ring is necessary.

The Celestron M42 Spacer Ring kit caters to various popular Celestron optical tubes and T-thread camera adapters, providing flexibility and precision in your astrophotography setup. Depending on your astrophotography method (DSLR or CCD/CMOS camera), the M42 Spacer Ring can be placed between your T-Ring and T-Adapter for optical tubes, or between the camera and T-Adapter.

This quick guide will help you choose the right spacer ring for EdgeHD, Schmidt-Cassegrain, and RASA 8 optical tubes:

7.5mm: Ideal for achieving proper spacing with the RASA 8 for many ZWO cameras.
12mm: Suitable for proper spacing with the RASA 8 for many Atik cameras.
30mm: Converts ZWO cameras with filter sliders to the 55mm back-focus standard for use with Schmidt-Cassegrain & EdgeHD.

Each M42 Spacer Ring is made from machined aluminum with a black anodized finish. The internal surfaces are blackened and glare-threaded to ensure the highest contrast, with a knurled surface for easy threading and unthreading. These rings are compatible with M42 x 0.75 (T-thread) camera adapters, making them a versatile and essential addition to your astrophotography gear.

Specifications

Thread:	M42 x 0.75
Spacer lengths:	7.5mm (.29"), 12mm (.47"), and 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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Celestron M42 Spacer Ring Kit

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