Celestron M42 Spacer Kit

With three different length spacer rings, this M42 Spacer Kit from Celestron allows for appropriate back-focus between Celestron optical tubes and T-thread camera adapters be achieved. Attaining the proper back focus for your camera-telescope system is critical. Without it, you'll see what appear to be elongated stars instead of pinpoints. This is because of reduced performance at the corners of full frame imaging sensors.

Take an 8" RASA with ZWO ASI183MC Pro camera for example:

• Required back-focus distance for 8" with included M42 camera adapter: 25 mm

• Back-focus consumed by the ZWO ASI183MC PRO: 17.5 mm

• For equal back-focus distance to be achieved, a 7.5 mm M42 spacer ring is required

Usage Instructions

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.

The three spacer rings included in this kit are listed below along with a quick guide to help you decide which spacer is best suited for Celestron's Schmidt-Cassegrain, EdgeHD, and RASA 8 optical tubes:

• 7.5 mm: Works best with the RASA 8 in combination with several ZWO cameras

• 12 mm: Works best with the RASA 8 in combination with several Atik cameras

• 30 mm: Converts ZWO cameras with a filter slider to 55 mm back-focus standard for use with SCT and EdgeHD

Exterior Body

Celestron M42 Spacer Rings are machined from black anodized aluminum with blackened and glare-threaded internal surfaces for maximum contrast. Each spacer ring has a knurled surface, providing a great gripping surface for threading/unthreading. Compatible with M42x0.75 (T-thread) camera adapters.

Celestron M42 Spacer Kit Highlights

• Enables optimal astro-imaging results by altering the back focus between your camera and telescope

• Kit includes 7.5 mm, 12 mm, and 30 mm spacer rings

• Threads to your T-Ring and T-Adapter with standard male and female T-Threads