Overcome the challenges of astrophotography with the M42 Spacer Ring Kit, expertly designed to help you achieve the optimal back-focus distance for your camera in relation to your telescope. This kit is essential for capturing the best astroimages, as an incorrect back-focus distance can lead to compromised performance at the corners of full-frame imaging sensors, resulting in elongated stars instead of precise pinpoints.For instance, when using a Rasa 8 with a Zwo Asi 183 Mc Pro camera, the required back-focus distance with the included M42 camera adapter is 25mm. However, the Zwo Asi 183 Mc Pro camera consumes a back-focus of 17.5mm. To equalize this back-focus distance, a 7.5mm M42 spacer ring from our kit is required.The M42 Spacer Ring Kit includes three differently sized spacer rings, allowing you to achieve the correct back-focus distance with various popular Celestron optical tubes and T-thread camera adapters. Using the M42 Spacer Ring is straightforward. If you're using a Dslr, simply place the appropriate M42 Spacer Ring between your T-Ring and your T-Adapter for your optical tube. For Ccd or Cmos camera users, place the desired M42 Spacer Ring between the camera and the T-Adapter for your optical tube.Each M42 Spacer Ring is crafted from machined aluminum and is black anodized. The internal surfaces are blackened and glare-threaded to provide the highest contrast. The spacer rings feature a knurled surface, ensuring a secure grip for easy threading and unthreading. These rings are compatible with M42 x 0.75 (T-thread) camera adapters.To assist you in choosing the correct spacer ring, here's a quick guide for our EdgeHD, Schmidt-Cassegrain, and Rasa 8 optical tubes: - The 7.5mm ring provides proper spacing with Rasa 8 for many Zwo cameras.- The 12mm ring offers correct spacing with Rasa 8 for numerous Atik cameras.- The 30mm ring converts Zwo camera with a filter slider to a 55mm back-focus standard for use with Schmidt-Cassegrain and EdgeHD.With the M42 Spacer Ring Kit, you can enhance your astrophotography experience, ensuring high-quality, precise images every time..