High resolution slit-free direct-viewing multiplexing field spectrograph

A spectrograph of 500 or greater resolution having no aperture-limiting slits or pinholes, comprising

• i) a single f/4 or lower entrance lens group of 3 mm or larger diameter, with each element aligned on a common optical axis, and not containing any cylindrical or aspheric elements,
• ii) at least one spectrally dispersive element selected from prisms and/or gratings,
• iii) an observation image plane distance from the entrance lens group at least 10 times the focal length of the entrance lens group, and
• iv) a viewing port after the dispersive elements for direct viewing of the spectrum with the unaided eye, or recording with standard retail consumer cameras with their integrated focusing elements
• v) optionally having a field lens prior to the entrance lens, selected from positive or negative elements, having aperture greater than the diameter of the entrance lens group,
• vi) optionally having a focusing element after the dispersive elements, positioned at a distance from the entrance lens group of at least 10× the focal length of the entrance lens group,
• vii) optionally having an array detector element at the focal plane of the focusing element in vii) to record the spectrum,
• viii) optionally having an attachment mechanism at the viewing port to secure a camera with its integrated focusing elements to record the spectrum,
• ix) optionally having a beam splitter positioned before or after the optional field lens, but before the entrance lens group, to enable simultaneous visual and spectrographic recording of objects in the field,
• x) optionally having a flip mirror positioned before or after the optional field lens, but before the entrance lens group to enable alternate visual and spectrographic recording of objects in the field,
• xi) optionally including filters or polarizing elements at any point in the optical path from before the field lens to the final observation port and/or image plane.