The FM-40 is a precision variable focusing microscope. When used with the included focusing screen, it will allow astrophotographers to achieve pinpoint focus for their photos. Correctly focused images will produce stunning enlargements.

The Takahashi focusing microsope can also be used as a terrestrial eyepiece. Screw in the .965 ocular adapter tube and place the FM-40 into a telescope. It will provide an erect image. By moving the drawtube, the focal length changes from 4mm to 6mm.