This Askar 1X Full Frame Flattener is designed specifically for the 140APO. It does not change the effective focal length of the telescope, which is f/7, but it DOES further flatten the field, correcting for both field curvature and coma, to reveal fine star points to the edges of the field. The Askar 1X Flattener has a triplet design and supports a 44 mm image circle. The telescope side has an M91*1 thread, and the camera side of the flattener has a built-in M48x0.75 (2") thread to accept filters and comes with three adapters (M68*1, M54*0.75, and M48*0.75). Both ends come with threaded metal caps to protect the optics when not in use. SPECIFICATIONS Lens Design: Triplet Back Focus: 55 mm from base of M48 male threads Telescope Focal Length with Flattener Attached: 980 mm Telescope Focal Ratio with Flattener Attached: f/7 Camera Side Thread Types: M68*1, M54*0.75, M48*0.75
