The 48mm T-Adapter is the accessory of choice if you'd like to attach your full frame DSLR or astronomical camera to a Celestron EdgeHD optical tube. With DSLR CCD chips getting larger, Celestron created the 48mm T-Adapter to reduce vignetting and provide a larger light path to your camera's sensor, producing exceptional astrophotos. The standard T-Adapter for EdgeHD 9.25", 11", and 14" comes with a 42mm T-Thread for a 42mm T-Ring. This smaller 42mm T-Adapter truncates the light cone coming from the back of the EdgeHD optical tubes, which creates vignetting in the corners of full frame imaging sensors. The 48mm T-Adapter has a larger T-Thread opening, allowing the unhindered light to illuminate the entire sensor, optimizing your full-frame sensor's capabilities.