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.