Undeflected

By sliding this prism in front of the spectrum I can deflect outward any portion of the spectrum I like, and by a mirror can reflect it through a second lens, forming a patch of light on the screen overlapping the patch of light formed by the undeflected rays.

A lump of matter flying in space might enter our solar system with such speed as to be able to pass through and go on its way almost undeflected.