The Celestron Off-Axis Guider is the simple solution to your telescope needs. The Celestron Off-Axis Lens Guider is an essential astroimaging accessory for long focal length telescopes that require the most accurate guiding possible. It uses a prism to intercept a small portion of the telescopeâ€™s focal plane (outside the field of view of the main imaging camera) to locate a guide star. Any movement seen by the guide star will be the exact same movement seen by the imaging camera. Guiding this way will correct for tracking errors, as well as opto-mechanical errors or flexure. The result: better astroimages with pinpoint round stars. Providing a large 12.5mm prism that can be adjusted to move closer to the center of the telescopeâ€™s focal plane, depending on the size of the imaging camera. This results in brighter guide stars, with the help of the large prism to fully illuminate the autoguider sensor. Featuring a high-quality, fixed-orientation Helical focuser. This provides extremely smooth and accurate focus of the autoguider without changing (or twisting) the autoguider camera orientation. Including all the needed spacers and adapters are included for most common imaging configurations, including DSLR cameras, Nightscape CCD cameras, and more. The following adapters are included with the Celestron Telescope Accessory: SCT/EdgeHD, female M48, female M42 (T-thread), male M48, male M42 (T-thread), 3 T-thread spacers.