Orion 8893 Field Flattener for Short Refractors

hi everyone i'm ken with orion telescopes and this here is the orion field flattener for fast refractors this is designed for any smaller refractor in the 400 to 650 millimeter focal length range there's a distortion at the edge of the field with those type of refractors if your ccd camera is big enough to see it the edges will be not as sharp as the center field curvature well the field flattener will correct that and give you nice sharp images from the center of the chip all the way to the edge of your frame it's fully multi-coated two elements 38 millimeter clear aperture for little to no vignetting depending on the size of your ccd camera chip and the front of it is threaded for filters so you can thread on a light pollution filter or any other imaging filter you so desire again the orion field flattener for fast refractors thank you very much you