The Explore Scientific Field Flattener for f/5 to f/7 Refractors
goes between your telescope and camera to correct coma aberration for
sharp images of stars in the corners of your photos. It is designed to
work with telescopes with focal ratios between f/5 and 7 and requires
55mm (±2mm) of spacing between the back of the device and the camera
This device is for photographic use only. It is not intended for visual use.