The typical DFM Engineering spectrograph is a Cassegrain instrument incorporating the standard features of a classical spectrograph used at classification dispersion.

The acquisition and guiding is performed by the Guide-Acquire-Module (GAM). The spectrograph optical system consists of the classical configuration and consists of the following subsystems:

Decker: A decker with different apertures is provided to define the slit length. The Decker is aluminized to allow acquisition and guiding. The apertures are remotely controlled.

Bilateral Adjustable Slit: The slit width is continuously variable over a wide range. The slit jaws are polished and set at a 6 degree angle to allow acquisition and guiding from the slit jaws. The slit width is remotely controlled.

Grating: Gratings are mounted in interchangeable cells. The grating and its cell are attached to a grating tilt stage allowing the resulting spectra to be positioned in the focal plane of the camera. A door in the spectrograph housing allows easy access to the grating and its cell so they may be easily changed. The grating tilt is remotely controlled.

Collimator: An off axis parabolic collimator is provided. The collimator is mounted on a stage allowing remote control of the focus.

Filter Wheel: A remotely controlled filter wheel is provided to allow the use of order separation filters.

Camera Lens: The typical camera consists of a commercial lens assembly mounted to a manually removable stage. Additional stages may be provided with different focal length lens assemblies.

Detector: A commercially available cooled and integrating CCD camera is provided.

Housing: The spectrograph is contained within an aluminum dust tight housing. A front flange allows attaching the spectrograph to the bolt pattern on the Guide-Acquire-Module.