The 48 mm 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 48 mm 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 42 mm T-Thread for a 42 mm T-Ring. This smaller 42 mm 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 48 mm T-Adapter has a larger T-Thread opening, allowing the unhindered light to illuminate the entire sensor, optimizing your full-frame sensor"_s capabilities.
Below, you will find the difference between the 42 mm and the 48 mm T-Rings to give you an idea of the space the 42 mm and 48 mm T-Threads on the T-Adapter will provide.
Note: The 48 mm T-Adapter will not offer any advantage to imagers with smaller APS-C sensors. For this, Celestron still recommends the 42 mm T-Adapter (#93646) and 42 mm T-Rings for your specific model of camera. T-Rings are sold separately. See our 42 mm Nikon T-Ring or Canon EOS T-Ring.
The chart below shows the relative illumination of the sensor in a 42 mm and a 48 mm T-Adapter. The X-axis is the distance from the center of the camera sensor. The Y-Axis is the amount of light being received. As you can see, the 48 mm receives more light than the 42 mm T-Adapter and will reduce vignetting in your images.