The field flattener & reducer for the ASKAR FRA 400 is a dedicated corrector with a reducing power of 0.7X. It shortens the focal length from 400mm to 280mm and the focal ratio from f/5.6 to f/3.9 halving the exposure time. The working distance between the flattener and the sensor is 55mm.
The flattener/reducer can be connected to the focuser of the Askar FRA 400 using the M68 x 1 male thread, on the camera side there is the universal M48 x 0.75 male thread. The flattener has an internal M48 x 0.75 thread to accept any standard 2" filter.
Spot diagram SharpStar 400 + 0.7x dedicated reducer